Merge pull request #2447 from bagerard/_changelog_0_22_0

prepare 0.22.0

.gitignore

@@ -1,8 +1,15 @@
-.*
 !.gitignore
 *~
 *.py[co]
 .*.sw[po]
+.cache/
+.coverage
+.coveragerc
+.env
+.idea/
+.pytest_cache/
+.tox/
+.eggs/
 *.egg
 docs/.build
 docs/_build
@@ -13,8 +20,6 @@ env/
 .settings
 .project
 .pydevproject
-tests/test_bugfix.py
 htmlcov/
 venv
 venv3
-scratchpad

.landscape.yml

@@ -1,22 +0,0 @@
-pylint:
-    disable:
-        # We use this a lot (e.g. via document._meta)
-        - protected-access
-
-    options:
-        additional-builtins:
-            # add xrange and long as valid built-ins. In Python 3, xrange is
-            # translated into range and long is translated into int via 2to3 (see
-            # "use_2to3" in setup.py). This should be removed when we drop Python
-            # 2 support (which probably won't happen any time soon).
-            - xrange
-            - long
-
-pyflakes:
-    disable:
-        # undefined variables are already covered by pylint (and exclude
-        # xrange & long)
-        - F821
-
-ignore-paths:
-    - benchmark.py

.pre-commit-config.yaml

@@ -0,0 +1,17 @@
+fail_fast: false
+repos:
+  - repo: https://github.com/ambv/black
+    rev: 20.8b1
+    hooks:
+      - id: black
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.4
+    hooks:
+      - id: flake8
+        additional_dependencies:
+          - flake8-import-order
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v2.7.4
+    hooks:
+      - id: pyupgrade
+        args: [--py36-plus]

.readthedocs.yml

@@ -0,0 +1,20 @@
+# .readthedocs.yml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+# Optionally set the version of Python and requirements required to build your docs
+python:
+  version: 3.7
+  install:
+    - requirements: docs/requirements.txt
+    # docs/conf.py is importing mongoengine
+    # so mongoengine needs to be installed as well
+    - method: setuptools
+      path: .

.travis.yml

@@ -1,13 +1,10 @@
 # For full coverage, we'd have to test all supported Python, MongoDB, and
 # PyMongo combinations. However, that would result in an overly long build
 # with a very large number of jobs, hence we only test a subset of all the
-# combinations:
+# combinations.
-# * MongoDB v3.4 & the latest PyMongo v3.x is currently the "main" setup,
+# * Python3.7, MongoDB v3.4 & the latest PyMongo v3.x is currently the "main" setup,
-#   tested against Python v2.7, v3.5, v3.6, v3.7, v3.8 and PyPy.
+# Other combinations are tested. See below for the details or check the travis jobs
-# * Besides that, we test the lowest actively supported Python/MongoDB/PyMongo
+
-#   combination: MongoDB v3.4, PyMongo v3.4, Python v2.7.
-# * MongoDB v3.6 is tested against Python v3.6, and PyMongo v3.6, v3.7, v3.8.
-#
 # We should periodically check MongoDB Server versions supported by MongoDB
 # Inc., add newly released versions to the test matrix, and remove versions
 # which have reached their End of Life. See:
@@ -16,41 +13,43 @@
 #
 # Reminder: Update README.rst if you change MongoDB versions we test.
 
-
 language: python
-python:
-- 2.7
-- 3.5
-- 3.6
-- 3.7
-- 3.8
-- pypy
-- pypy3
-
 dist: xenial
+python:
+  - 3.6
+  - 3.7
+  - 3.8
+  - 3.9
+  - pypy3
 
 env:
   global:
-    - MONGODB_3_4=3.4.17
+    - MONGODB_3_4=3.4.19
-    - MONGODB_3_6=3.6.12
+    - MONGODB_3_6=3.6.13
-    - PYMONGO_3_9=3.9
+    - MONGODB_4_0=4.0.13
-    - PYMONGO_3_6=3.6
+
     - PYMONGO_3_4=3.4
+    - PYMONGO_3_6=3.6
+    - PYMONGO_3_9=3.9
+    - PYMONGO_3_11=3.11
+
+    - MAIN_PYTHON_VERSION=3.7
   matrix:
-    - MONGODB=${MONGODB_3_4} PYMONGO=${PYMONGO_3_9}
+    - MONGODB=${MONGODB_3_4} PYMONGO=${PYMONGO_3_11}
 
 matrix:
-
   # Finish the build as soon as one job fails
   fast_finish: true
 
   include:
-  - python: 2.7
+    - python: 3.7
-    env: MONGODB=${MONGODB_3_4} PYMONGO=${PYMONGO_3_4}
+      env: MONGODB=${MONGODB_3_6} PYMONGO=${PYMONGO_3_6}
-  - python: 3.7
+    - python: 3.7
-    env: MONGODB=${MONGODB_3_6} PYMONGO=${PYMONGO_3_6}
+      env: MONGODB=${MONGODB_3_6} PYMONGO=${PYMONGO_3_9}
-  - python: 3.7
+    - python: 3.7
-    env: MONGODB=${MONGODB_3_6} PYMONGO=${PYMONGO_3_9}
+      env: MONGODB=${MONGODB_3_6} PYMONGO=${PYMONGO_3_11}
+    - python: 3.8
+      env: MONGODB=${MONGODB_4_0} PYMONGO=${PYMONGO_3_11}
 
 install:
   # Install Mongo
@@ -60,29 +59,23 @@ install:
   # Install Python dependencies.
   - pip install --upgrade pip
   - pip install coveralls
-  - pip install flake8 flake8-import-order
+  - pip install pre-commit
-  - pip install tox         # tox 3.11.0 has requirement virtualenv>=14.0.0
+  - pip install tox
-  - pip install virtualenv  # virtualenv>=14.0.0 has dropped Python 3.2 support (and pypy3 is based on py32)
   # tox dryrun to setup the tox venv (we run a mock test).
   - tox -e $(echo py$TRAVIS_PYTHON_VERSION-mg$PYMONGO | tr -d . | sed -e 's/pypypy/pypy/') -- -a "-k=test_ci_placeholder"
-  # Install black for Python v3.7 only.
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.7' ]]; then pip install black; fi
 
 before_script:
   - mkdir ${PWD}/mongodb-linux-x86_64-${MONGODB}/data
   - ${PWD}/mongodb-linux-x86_64-${MONGODB}/bin/mongod --dbpath ${PWD}/mongodb-linux-x86_64-${MONGODB}/data --logpath ${PWD}/mongodb-linux-x86_64-${MONGODB}/mongodb.log --fork
-  - if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then flake8 .; else echo "flake8 only runs on py27"; fi   # Run flake8 for Python 2.7 only
+  # Run pre-commit hooks (black, flake8, etc) on entire codebase
-  - if [[ $TRAVIS_PYTHON_VERSION == '3.7' ]]; then black --check .; else echo "black only runs on py37"; fi   # Run black for Python 3.7 only
+  - if [[ $TRAVIS_PYTHON_VERSION == $MAIN_PYTHON_VERSION ]]; then pre-commit run -a; else echo "pre-commit checks only runs on py37"; fi
-  - mongo --eval 'db.version();'    # Make sure mongo is awake
+  - mongo --eval 'db.version();' # Make sure mongo is awake
 
 script:
   - tox -e $(echo py$TRAVIS_PYTHON_VERSION-mg$PYMONGO | tr -d . | sed -e 's/pypypy/pypy/') -- -a "--cov=mongoengine"
 
-# For now only submit coveralls for Python v2.7. Python v3.x currently shows
-# 0% coverage. That's caused by 'use_2to3', which builds the py3-compatible
-# code in a separate dir and runs tests on that.
 after_success:
-- if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then coveralls --verbose; else echo "coveralls only sent for py27"; fi
+  - if [[ $TRAVIS_PYTHON_VERSION == $MAIN_PYTHON_VERSION ]]; then coveralls --verbose; else echo "coveralls only sent for py37"; fi
 
 notifications:
   irc: irc.freenode.org#mongoengine
@@ -90,8 +83,8 @@ notifications:
 # Only run builds on the master branch and GitHub releases (tagged as vX.Y.Z)
 branches:
   only:
-  - master
+    - master
-  - /^v.*$/
+    - /^v.*$/
 
 # Whenever a new release is created via GitHub, publish it on PyPI.
 deploy:
@@ -104,11 +97,11 @@ deploy:
   distributions: "sdist bdist_wheel"
 
   # Only deploy on tagged commits (aka GitHub releases) and only for the parent
-  # repo's builds running Python v2.7 along with PyMongo v3.x and MongoDB v3.4.
+  # repo's builds running Python v3.7 along with PyMongo v3.x and MongoDB v3.4.
   # We run Travis against many different Python, PyMongo, and MongoDB versions
   # and we don't want the deploy to occur multiple times).
   on:
     tags: true
     repo: MongoEngine/mongoengine
-    condition: ($PYMONGO = ${PYMONGO_3_9}) && ($MONGODB = ${MONGODB_3_4})
+    condition: ($PYMONGO = ${PYMONGO_3_11}) && ($MONGODB = ${MONGODB_3_4})
-    python: 2.7
+    python: 3.7

AUTHORS

@@ -255,3 +255,7 @@ that much better:
  * Filip Kucharczyk (https://github.com/Pacu2)
  * Eric Timmons (https://github.com/daewok)
  * Matthew Simpson (https://github.com/mcsimps2)
+ * Leonardo Domingues (https://github.com/leodmgs)
+ * Agustin Barto (https://github.com/abarto)
+ * Stankiewicz Mateusz (https://github.com/mas15)
+ * Felix Schultheiß (https://github.com/felix-smashdocs)

CONTRIBUTING.rst

@@ -20,19 +20,43 @@ post to the `user group <http://groups.google.com/group/mongoengine-users>`
 Supported Interpreters
 ----------------------
 
-MongoEngine supports CPython 2.7 and newer. Language
+MongoEngine supports CPython 3.5 and newer as well as Pypy3.
-features not supported by all interpreters can not be used.
+Language features not supported by all interpreters can not be used.
-The codebase is written in python 2 so you must be using python 2
+
-when developing new features. Compatibility of the library with Python 3
+Python3 codebase
-relies on the 2to3 package that gets executed as part of the installation
+----------------------
-build. You should ensure that your code is properly converted by
+
-`2to3 <http://docs.python.org/library/2to3.html>`_.
+Since 0.20, the codebase is exclusively Python 3.
+
+Earlier versions were exclusively Python2, and were relying on 2to3 to support Python3 installs.
+Travis runs the tests against the main Python 3.x versions.
+
 
 Style Guide
 -----------
 
-MongoEngine uses `black <https://github.com/python/black>`_ for code
+MongoEngine's codebase is formatted with `black <https://github.com/python/black>`_, other tools like
-formatting.
+flake8 are also used. Those tools will run as part of the CI and will fail in case the code is not formatted properly.
+
+To install all development tools, simply run the following commands:
+
+.. code-block:: console
+
+    $ python -m pip install -r requirements-dev.txt
+
+
+You can install `pre-commit <https://pre-commit.com/>`_ into your git hooks,
+to automatically check and fix any formatting issue before creating a
+git commit.
+
+To enable ``pre-commit`` simply run:
+
+.. code-block:: console
+
+    $ pre-commit install
+
+See the ``.pre-commit-config.yaml`` configuration file for more information
+on how it works.
 
 Testing
 -------

README.rst

@@ -12,9 +12,8 @@ MongoEngine
 .. image:: https://coveralls.io/repos/github/MongoEngine/mongoengine/badge.svg?branch=master
   :target: https://coveralls.io/github/MongoEngine/mongoengine?branch=master
 
-.. image:: https://landscape.io/github/MongoEngine/mongoengine/master/landscape.svg?style=flat
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
-  :target: https://landscape.io/github/MongoEngine/mongoengine/master
+  :target: https://github.com/ambv/black
-  :alt: Code Health
 
 About
 =====
@@ -26,15 +25,15 @@ an `API reference <https://mongoengine-odm.readthedocs.io/apireference.html>`_.
 
 Supported MongoDB Versions
 ==========================
-MongoEngine is currently tested against MongoDB v3.4 and v3.6. Future versions
+MongoEngine is currently tested against MongoDB v3.4, v3.6 and v4.0. Future versions
 should be supported as well, but aren't actively tested at the moment. Make
 sure to open an issue or submit a pull request if you experience any problems
-with MongoDB version > 3.6.
+with MongoDB version > 4.0.
 
 Installation
 ============
 We recommend the use of `virtualenv <https://virtualenv.pypa.io/>`_ and of
-`pip <https://pip.pypa.io/>`_. You can then use ``pip install -U mongoengine``.
+`pip <https://pip.pypa.io/>`_. You can then use ``python -m pip install -U mongoengine``.
 You may also have `setuptools <http://peak.telecommunity.com/DevCenter/setuptools>`_
 and thus you can use ``easy_install -U mongoengine``. Another option is
 `pipenv <https://docs.pipenv.org/>`_. You can then use ``pipenv install mongoengine``
@@ -42,13 +41,14 @@ to both create the virtual environment and install the package. Otherwise, you c
 download the source from `GitHub <http://github.com/MongoEngine/mongoengine>`_ and
 run ``python setup.py install``.
 
+The support for Python2 was dropped with MongoEngine 0.20.0
+
 Dependencies
 ============
-All of the dependencies can easily be installed via `pip <https://pip.pypa.io/>`_.
+All of the dependencies can easily be installed via `python -m pip <https://pip.pypa.io/>`_.
 At the very least, you'll need these two packages to use MongoEngine:
 
 - pymongo>=3.4
-- six>=1.10.0
 
 If you utilize a ``DateTimeField``, you might also use a more flexible date parser:
 
@@ -58,6 +58,10 @@ If you need to use an ``ImageField`` or ``ImageGridFsProxy``:
 
 - Pillow>=2.0.0
 
+If you need to use signals:
+
+- blinker>=1.3
+
 Examples
 ========
 Some simple examples of what MongoEngine code looks like:
@@ -125,7 +129,7 @@ installed in your environment and then:
 .. code-block:: shell
 
     # Install tox
-    $ pip install tox
+    $ python -m pip install tox
     # Run the test suites
     $ tox
 

benchmarks/test_basic_doc_ops.py

@@ -45,7 +45,7 @@ def test_basic():
 
     print(
         "Doc setattr: %.3fus"
-        % (timeit(lambda: setattr(b, "name", "New name"), 10000) * 10 ** 6)
+        % (timeit(lambda: setattr(b, "name", "New name"), 10000) * 10 ** 6)  # noqa B010
     )
 
     print("Doc to mongo: %.3fus" % (timeit(b.to_mongo, 1000) * 10 ** 6))

benchmarks/test_inserts.py

@@ -4,12 +4,14 @@ import timeit
 def main():
     setup = """
 from pymongo import MongoClient
+
 connection = MongoClient()
 connection.drop_database('mongoengine_benchmark_test')
 """
 
     stmt = """
 from pymongo import MongoClient
+
 connection = MongoClient()
 
 db = connection.mongoengine_benchmark_test
@@ -56,6 +58,7 @@ myNoddys = noddy.find()
 
     setup = """
 from pymongo import MongoClient
+
 connection = MongoClient()
 connection.drop_database('mongoengine_benchmark_test')
 connection.close()

docs/Makefile

@@ -33,7 +33,7 @@ clean:
 html:
 	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
 	@echo
-	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."
+	@echo "Build finished. Check $(BUILDDIR)/html/index.html"
 
 dirhtml:
 	$(SPHINXBUILD) -b dirhtml $(ALLSPHINXOPTS) $(BUILDDIR)/dirhtml

docs/changelog.rst

@@ -7,9 +7,51 @@ Development
 ===========
 - (Fill this out as you fix issues and develop your features).
 
+Changes in 0.22.0
+=================
+- Fix LazyReferenceField dereferencing in embedded documents #2426
+- Fix regarding the recent use of Cursor.__spec in .count() that was interfering with mongomock #2425
+- Drop support for Python 3.5 by introducing f-strings in the codebase
+
+Changes in 0.21.0
+=================
+- Bug fix in DynamicDocument which is not parsing known fields in constructor like Document do #2412
+- When using pymongo >= 3.7, make use of Collection.count_documents instead of Collection.count
+    and Cursor.count that got deprecated in pymongo >= 3.7.
+    This should have a negative impact on performance of count see Issue #2219
+- Fix a bug that made the queryset drop the read_preference after clone().
+- Remove Py3.5 from CI as it reached EOL and add Python 3.9
+- Fix some issues related with db_field/field conflict in constructor #2414
+- BREAKING CHANGE: Fix the behavior of Doc.objects.limit(0) which should return all documents (similar to mongodb) #2311
+- Bug fix in ListField when updating the first item, it was saving the whole list, instead of
+    just replacing the first item (as usually done when updating 1 item of the list) #2392
+- Add EnumField: ``mongoengine.fields.EnumField``
+- Refactoring - Remove useless code related to Document.__only_fields and Queryset.only_fields
+- Fix query transformation regarding special operators #2365
+- Bug Fix: Document.save() fails when shard_key is not _id #2154
+
+Changes in 0.20.0
+=================
+- ATTENTION: Drop support for Python2
+- Add Mongo 4.0 to Travis
+- Fix error when setting a string as a ComplexDateTimeField #2253
+- Bump development Status classifier to Production/Stable #2232
+- Improve Queryset.get to avoid confusing MultipleObjectsReturned message in case multiple match are found #630
+- Fixed a bug causing inaccurate query results, while combining ``__raw__`` and regular filters for the same field #2264
+- Add support for the `elemMatch` projection operator in .fields() (e.g BlogPost.objects.fields(elemMatch__comments="test")) #2267
+- DictField validate failed without default connection (bug introduced in 0.19.0) #2239
+- Remove methods that were deprecated years ago:
+    - name parameter in Field constructor e.g `StringField(name="...")`, was replaced by db_field
+    - Queryset.slave_okay() was deprecated since pymongo3
+    - dropDups was dropped with MongoDB3
+    - ``Queryset._ensure_indexes`` and ``Queryset.ensure_indexes``, the right method to use is ``Document.ensure_indexes``
+- Added pre-commit for development/CI #2212
+- Renamed requirements-lint.txt to requirements-dev.txt #2212
+- Support for setting ReadConcern #2255
+
 Changes in 0.19.1
 =================
-- Requires Pillow < 7.0.0 as it dropped Python2 support
+- Tests require Pillow < 7.0.0 as it dropped Python2 support
 - DEPRECATION: The interface of ``QuerySet.aggregate`` method was changed, it no longer takes an unpacked list of
     pipeline steps (*pipeline) but simply takes the pipeline list just like ``pymongo.Collection.aggregate`` does. #2079
 
@@ -437,9 +479,6 @@ Changes in 0.8.3
 - Document.select_related() now respects ``db_alias`` (#377)
 - Reload uses shard_key if applicable (#384)
 - Dynamic fields are ordered based on creation and stored in _fields_ordered (#396)
-
-  **Potential breaking change:** http://docs.mongoengine.org/en/latest/upgrade.html#to-0-8-3
-
 - Fixed pickling dynamic documents ``_dynamic_fields`` (#387)
 - Fixed ListField setslice and delslice dirty tracking (#390)
 - Added Django 1.5 PY3 support (#392)

docs/conf.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 #
 # MongoEngine documentation build configuration file, created by
 # sphinx-quickstart on Sun Nov 22 18:14:13 2009.
@@ -42,8 +41,8 @@ source_suffix = ".rst"
 master_doc = "index"
 
 # General information about the project.
-project = u"MongoEngine"
+project = "MongoEngine"
-copyright = u"2009, MongoEngine Authors"
+copyright = "2009, MongoEngine Authors"  # noqa: A001
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the

docs/django.rst

@@ -13,7 +13,7 @@ Help Wanted!
 
 The MongoEngine team is looking for help contributing and maintaining a new
 Django extension for MongoEngine! If you have Django experience and would like
-to help contribute to the project, please get in touch on the 
+to help contribute to the project, please get in touch on the
-`mailing list <http://groups.google.com/group/mongoengine-users>`_ or by 
+`mailing list <http://groups.google.com/group/mongoengine-users>`_ or by
 simply contributing on
 `GitHub <https://github.com/MongoEngine/django-mongoengine>`_.

docs/faq.rst

@@ -10,4 +10,3 @@ If this is a requirement for your project, check the alternative:  `uMongo`_ and
 
 .. _uMongo: https://umongo.readthedocs.io/
 .. _MotorEngine: https://motorengine.readthedocs.io/
-

docs/guide/connecting.rst

@@ -31,6 +31,8 @@ the :attr:`host` to
 
     connect('project1', host='mongodb://localhost/database_name')
 
+.. note:: URI containing SRV records (e.g mongodb+srv://server.example.com/) can be used as well as the :attr:`host`
+
 .. note:: Database, username and password from URI string overrides
     corresponding parameters in :func:`~mongoengine.connect`: ::
 
@@ -86,7 +88,7 @@ using 3 different databases to store data::
         connect(alias='user-db-alias', db='user-db')
         connect(alias='book-db-alias', db='book-db')
         connect(alias='users-books-db-alias', db='users-books-db')
-        
+
         class User(Document):
             name = StringField()
 

docs/guide/defining-documents.rst

@@ -76,6 +76,7 @@ are as follows:
 * :class:`~mongoengine.fields.EmailField`
 * :class:`~mongoengine.fields.EmbeddedDocumentField`
 * :class:`~mongoengine.fields.EmbeddedDocumentListField`
+* :class:`~mongoengine.fields.EnumField`
 * :class:`~mongoengine.fields.FileField`
 * :class:`~mongoengine.fields.FloatField`
 * :class:`~mongoengine.fields.GenericEmbeddedDocumentField`
@@ -426,19 +427,6 @@ either a single field name, or a list or tuple of field names::
         first_name = StringField()
         last_name = StringField(unique_with='first_name')
 
-Skipping Document validation on save
-------------------------------------
-You can also skip the whole document validation process by setting
-``validate=False`` when calling the :meth:`~mongoengine.document.Document.save`
-method::
-
-    class Recipient(Document):
-        name = StringField()
-        email = EmailField()
-
-    recipient = Recipient(name='admin', email='root@localhost')
-    recipient.save()               # will raise a ValidationError while
-    recipient.save(validate=False) # won't
 
 Document collections
 ====================
@@ -555,7 +543,6 @@ There are a few top level defaults for all indexes that can be set::
             'index_background': True,
             'index_cls': False,
             'auto_create_index': True,
-            'index_drop_dups': True,
         }
 
 
@@ -574,11 +561,6 @@ There are a few top level defaults for all indexes that can be set::
     in systems where indexes are managed separately. Disabling this will improve
     performance.
 
-:attr:`index_drop_dups` (Optional)
-    Set the default value for if an index should drop duplicates
-    Since MongoDB 3.0 drop_dups is not supported anymore. Raises a Warning
-    and has no effect
-
 
 Compound Indexes and Indexing sub documents
 -------------------------------------------

docs/guide/document-instances.rst

@@ -41,35 +41,6 @@ already exist, then any changes will be updated atomically.  For example::
 .. seealso::
     :ref:`guide-atomic-updates`
 
-Pre save data validation and cleaning
--------------------------------------
-MongoEngine allows you to create custom cleaning rules for your documents when
-calling :meth:`~mongoengine.Document.save`.  By providing a custom
-:meth:`~mongoengine.Document.clean` method you can do any pre validation / data
-cleaning.
-
-This might be useful if you want to ensure a default value based on other
-document values for example::
-
-    class Essay(Document):
-        status = StringField(choices=('Published', 'Draft'), required=True)
-        pub_date = DateTimeField()
-
-        def clean(self):
-            """Ensures that only published essays have a `pub_date` and
-            automatically sets `pub_date` if essay is published and `pub_date`
-            is not set"""
-            if self.status == 'Draft' and self.pub_date is not None:
-                msg = 'Draft entries should not have a publication date.'
-                raise ValidationError(msg)
-            # Set the pub_date for published items if not set.
-            if self.status == 'Published' and self.pub_date is None:
-                self.pub_date = datetime.now()
-
-.. note::
-    Cleaning is only called if validation is turned on and when calling
-    :meth:`~mongoengine.Document.save`.
-
 Cascading Saves
 ---------------
 If your document contains :class:`~mongoengine.fields.ReferenceField` or

docs/guide/gridfs.rst

@@ -2,8 +2,6 @@
 GridFS
 ======
 
-.. versionadded:: 0.4
-
 Writing
 -------
 

docs/guide/index.rst

@@ -10,8 +10,10 @@ User Guide
    defining-documents
    document-instances
    querying
+   validation
    gridfs
    signals
    text-indexes
+   migration
    logging-monitoring
    mongomock

docs/guide/installing.rst

@@ -12,7 +12,7 @@ MongoEngine is available on PyPI, so you can use :program:`pip`:
 
 .. code-block:: console
 
-    $ pip install mongoengine
+    $ python -m pip install mongoengine
 
 Alternatively, if you don't have setuptools installed, `download it from PyPi
 <http://pypi.python.org/pypi/mongoengine/>`_ and run

docs/guide/migration.rst

@@ -0,0 +1,267 @@
+===================
+Documents migration
+===================
+
+The structure of your documents and their associated mongoengine schemas are likely
+to change over the lifetime of an application. This section provides guidance and
+recommendations on how to deal with migrations.
+
+Due to the very flexible nature of mongodb, migrations of models aren't trivial and
+for people that know about `alembic` for `sqlalchemy`, there is unfortunately no equivalent
+library that will manage the migration in an automatic fashion for mongoengine.
+
+Example 1: Addition of a field
+==============================
+
+Let's start by taking a simple example of a model change and review the different option you
+have to deal with the migration.
+
+Let's assume we start with the following schema and save an instance:
+
+.. code-block:: python
+
+    class User(Document):
+        name = StringField()
+
+    User(name="John Doe").save()
+
+    # print the objects as they exist in mongodb
+    print(User.objects().as_pymongo())    # [{u'_id': ObjectId('5d06b9c3d7c1f18db3e7c874'), u'name': u'John Doe'}]
+
+On the next version of your application, let's now assume that a new field `enabled` gets added to the
+existing ``User`` model with a `default=True`. Thus you simply update the ``User`` class to the following:
+
+.. code-block:: python
+
+    class User(Document):
+        name = StringField(required=True)
+        enabled = BooleaField(default=True)
+
+Without applying any migration, we now reload an object from the database into the ``User`` class
+and checks its `enabled` attribute:
+
+.. code-block:: python
+
+    assert User.objects.count() == 1
+    user = User.objects().first()
+    assert user.enabled is True
+    assert User.objects(enabled=True).count() == 0    # uh?
+    assert User.objects(enabled=False).count() == 0   # uh?
+
+    # this is consistent with what we have in the database
+    # in fact, 'enabled' does not exist
+    print(User.objects().as_pymongo().first())    # {u'_id': ObjectId('5d06b9c3d7c1f18db3e7c874'), u'name': u'John'}
+    assert User.objects(enabled=None).count() == 1
+
+As you can see, even if the document wasn't updated, mongoengine applies the default value seamlessly when it
+loads the pymongo dict into a ``User`` instance. At first sight it looks like you don't need to migrate the
+existing documents when adding new fields but this actually leads to inconsistencies when it comes to querying.
+
+In fact, when querying, mongoengine isn't trying to account for the default value of the new field and so
+if you don't actually migrate the existing documents, you are taking a risk that querying/updating
+will be missing relevant record.
+
+When adding fields/modifying default values, you can use any of the following to do the migration
+as a standalone script:
+
+.. code-block:: python
+
+    # Use mongoengine to set a default value for a given field
+    User.objects().update(enabled=True)
+    # or use pymongo
+    user_coll = User._get_collection()
+    user_coll.update_many({}, {'$set': {'enabled': True}})
+
+
+Example 2: Inheritance change
+=============================
+
+Let's consider the following example:
+
+.. code-block:: python
+
+    class Human(Document):
+        name = StringField()
+        meta = {"allow_inheritance": True}
+
+    class Jedi(Human):
+        dark_side = BooleanField()
+        light_saber_color = StringField()
+
+    Jedi(name="Darth Vader", dark_side=True, light_saber_color="red").save()
+    Jedi(name="Obi Wan Kenobi", dark_side=False, light_saber_color="blue").save()
+
+    assert Human.objects.count() == 2
+    assert Jedi.objects.count() == 2
+
+    # Let's check how these documents got stored in mongodb
+    print(Jedi.objects.as_pymongo())
+    # [
+    #   {'_id': ObjectId('5fac4aaaf61d7fb06046e0f9'), '_cls': 'Human.Jedi', 'name': 'Darth Vader', 'dark_side': True, 'light_saber_color': 'red'},
+    #   {'_id': ObjectId('5fac4ac4f61d7fb06046e0fa'), '_cls': 'Human.Jedi', 'name': 'Obi Wan Kenobi', 'dark_side': False, 'light_saber_color': 'blue'}
+    # ]
+
+As you can observe, when you use inheritance, MongoEngine stores a field named '_cls' behind the scene to keep
+track of the Document class.
+
+Let's now take the scenario that you want to refactor the inheritance schema and:
+- Have the Jedi's with dark_side=True/False become GoodJedi's/DarkSith
+- get rid of the 'dark_side' field
+
+move to the following schemas:
+
+.. code-block:: python
+
+    # unchanged
+    class Human(Document):
+        name = StringField()
+        meta = {"allow_inheritance": True}
+
+    # attribute 'dark_side' removed
+    class GoodJedi(Human):
+        light_saber_color = StringField()
+
+    # new class
+    class BadSith(Human):
+        light_saber_color = StringField()
+
+MongoEngine doesn't know about the change or how to map them with the existing data
+so if you don't apply any migration, you will observe a strange behavior, as if the collection was suddenly
+empty.
+
+.. code-block:: python
+
+    # As a reminder, the documents that we inserted
+    # have the _cls field = 'Human.Jedi'
+
+    # Following has no match
+    # because the query that is used behind the scene is
+    # filtering on {'_cls': 'Human.GoodJedi'}
+    assert GoodJedi.objects().count() == 0
+
+    # Following has also no match
+    # because it is filtering on {'_cls': {'$in': ('Human', 'Human.GoodJedi', 'Human.BadSith')}}
+    # which has no match
+    assert Human.objects.count() == 0
+    assert Human.objects.first() is None
+
+    # If we bypass MongoEngine and make use of underlying driver (PyMongo)
+    # we can see that the documents are there
+    humans_coll = Human._get_collection()
+    assert humans_coll.count_documents({}) == 2
+    # print first document
+    print(humans_coll.find_one())
+    # {'_id': ObjectId('5fac4aaaf61d7fb06046e0f9'), '_cls': 'Human.Jedi', 'name': 'Darth Vader', 'dark_side': True, 'light_saber_color': 'red'}
+
+As you can see, first obvious problem is that we need to modify '_cls' values based on existing values of
+'dark_side' documents.
+
+.. code-block:: python
+
+    humans_coll = Human._get_collection()
+    old_class = 'Human.Jedi'
+    good_jedi_class = 'Human.GoodJedi'
+    bad_sith_class = 'Human.BadSith'
+    humans_coll.update_many({'_cls': old_class, 'dark_side': False}, {'$set': {'_cls': good_jedi_class}})
+    humans_coll.update_many({'_cls': old_class, 'dark_side': True}, {'$set': {'_cls': bad_sith_class}})
+
+Let's now check if querying improved in MongoEngine:
+
+.. code-block:: python
+
+    assert GoodJedi.objects().count() == 1  # Hoorah!
+    assert BadSith.objects().count() == 1   # Hoorah!
+    assert Human.objects.count() == 2       # Hoorah!
+
+    # let's now check that documents load correctly
+    jedi = GoodJedi.objects().first()
+    # raises FieldDoesNotExist: The fields "{'dark_side'}" do not exist on the document "Human.GoodJedi"
+
+In fact we only took care of renaming the _cls values but we havn't removed the 'dark_side' fields
+which does not exist anymore on the GoodJedi's and BadSith's models.
+Let's remove the field from the collections:
+
+.. code-block:: python
+
+    humans_coll = Human._get_collection()
+    humans_coll.update_many({}, {'$unset': {'dark_side': 1}})
+
+.. note:: We did this migration in 2 different steps for the sake of example but it could have been combined
+    with the migration of the _cls fields: ::
+
+        humans_coll.update_many(
+            {'_cls': old_class, 'dark_side': False},
+            {
+                '$set': {'_cls': good_jedi_class},
+                '$unset': {'dark_side': 1}
+            }
+        )
+
+
+And verify that the documents now load correctly:
+
+.. code-block:: python
+
+    jedi = GoodJedi.objects().first()
+    assert jedi.name == "Obi Wan Kenobi"
+
+    sith = BadSith.objects().first()
+    assert sith.name == "Darth Vader"
+
+
+An other way of dealing with this migration is to iterate over
+the documents and update/replace them one by one. This is way slower but
+it is often useful for complex migrations of Document models.
+
+.. code-block:: python
+
+    for doc in humans_coll.find():
+        if doc['_cls'] == 'Human.Jedi':
+            doc['_cls'] =  'Human.BadSith' if doc['dark_side'] else 'Human.GoodJedi'
+            doc.pop('dark_side')
+            humans_coll.replace_one({'_id': doc['_id']}, doc)
+
+.. warning:: Be aware of this `flaw <https://groups.google.com/g/mongodb-user/c/AFC1ia7MHzk>`_ if you modify documents while iterating
+
+Recommendations
+===============
+
+- Write migration scripts whenever you do changes to the model schemas
+- Using :class:`~mongoengine.DynamicDocument` or ``meta = {"strict": False}`` may help to avoid some migrations or to have the 2 versions of your application to co-exist.
+- Write post-processing checks to verify that migrations script worked. See below
+
+Post-processing checks
+======================
+
+The following recipe can be used to sanity check a Document collection after you applied migration.
+It does not make any assumption on what was migrated, it will fetch 1000 objects randomly and
+run some quick checks on the documents to make sure the document looks OK. As it is, it will fail
+on the first occurrence of an error but this is something that can be adapted based on your needs.
+
+.. code-block:: python
+
+    def get_random_oids(collection, sample_size):
+        pipeline = [{"$project": {'_id': 1}}, {"$sample": {"size": sample_size}}]
+        return [s['_id'] for s in collection.aggregate(pipeline)]
+
+    def get_random_documents(DocCls, sample_size):
+        doc_collection = DocCls._get_collection()
+        random_oids = get_random_oids(doc_collection, sample_size)
+        return DocCls.objects(id__in=random_oids)
+
+    def check_documents(DocCls, sample_size):
+        for doc in get_random_documents(DocCls, sample_size):
+            # general validation (types and values)
+            doc.validate()
+
+            # load all subfields,
+            # this may trigger additional queries if you have ReferenceFields
+            # so it may be slow
+            for field in doc._fields:
+                try:
+                    getattr(doc, field)
+                except Exception:
+                    LOG.warning(f"Could not load field {field} in Document {doc.id}")
+                    raise
+
+    check_documents(Human, sample_size=1000)

docs/guide/querying.rst

@@ -609,7 +609,7 @@ to push values with index::
 .. note::
     Currently only top level lists are handled, future versions of mongodb /
     pymongo plan to support nested positional operators.  See `The $ positional
-    operator <http://www.mongodb.org/display/DOCS/Updating#Updating-The%24positionaloperator>`_.
+    operator <https://docs.mongodb.com/manual/tutorial/update-documents/#Updating-The%24positionaloperator>`_.
 
 Server-side javascript execution
 ================================

docs/guide/signals.rst

@@ -44,8 +44,8 @@ Available signals include:
 
 `post_save`
   Called within :meth:`~mongoengine.Document.save` after most actions
-  (validation, insert/update, and cascades, but not clearing dirty flags) have 
+  (validation, insert/update, and cascades, but not clearing dirty flags) have
-  completed successfully.  Passed the additional boolean keyword argument 
+  completed successfully.  Passed the additional boolean keyword argument
   `created` to indicate if the save was an insert or an update.
 
 `pre_delete`

docs/guide/text-indexes.rst

@@ -8,7 +8,7 @@ After MongoDB 2.4 version, supports search documents by text indexes.
 Defining a Document with text index
 ===================================
 Use the *$* prefix to set a text index, Look the declaration::
-  
+
   class News(Document):
       title = StringField()
       content = StringField()
@@ -35,10 +35,10 @@ Saving a document::
        content="Various improvements").save()
 
 Next, start a text search using :attr:`QuerySet.search_text` method::
-  
+
   document = News.objects.search_text('testing').first()
   document.title # may be: "Using mongodb text search"
-  
+
   document = News.objects.search_text('released').first()
   document.title # may be: "MongoEngine 0.9 released"
 

docs/guide/validation.rst

@@ -0,0 +1,123 @@
+====================
+Document Validation
+====================
+
+By design, MongoEngine strictly validates the documents right before they are inserted in MongoDB
+and makes sure they are consistent with the fields defined in your models.
+
+MongoEngine makes the assumption that the documents that exists in the DB are compliant with the schema.
+This means that Mongoengine will not validate a document when an object is loaded from the DB into an instance
+of your model but this operation may fail under some circumstances (e.g. if there is a field in
+the document fetched from the database that is not defined in your model).
+
+
+Built-in validation
+===================
+
+Mongoengine provides different fields that encapsulate the corresponding validation
+out of the box. Validation runs when calling `.validate()` or `.save()`
+
+.. code-block:: python
+
+    from mongoengine import Document, EmailField
+
+    class User(Document):
+        email = EmailField()
+        age = IntField(min_value=0, max_value=99)
+
+    user = User(email='invalid@', age=24)
+    user.validate()     # raises ValidationError (Invalid email address: ['email'])
+    user.save()         # raises ValidationError (Invalid email address: ['email'])
+
+    user2 = User(email='john.doe@garbage.com', age=1000)
+    user2.save()        # raises ValidationError (Integer value is too large: ['age'])
+
+Custom validation
+=================
+
+The following feature can be used to customize the validation:
+
+* Field `validation` parameter
+
+.. code-block:: python
+
+    def not_john_doe(name):
+        if name == 'John Doe':
+            raise ValidationError("John Doe is not a valid name")
+
+    class Person(Document):
+        full_name = StringField(validation=not_john_doe)
+
+    Person(full_name='Billy Doe').save()
+    Person(full_name='John Doe').save()  # raises ValidationError (John Doe is not a valid name)
+
+
+* Document `clean` method
+
+This method is called as part of :meth:`~mongoengine.document.Document.save` and should be used to provide
+custom model validation and/or to modify some of the field values prior to validation.
+For instance, you could use it to automatically provide a value for a field, or to do validation
+that requires access to more than a single field.
+
+.. code-block:: python
+
+    class Essay(Document):
+        status = StringField(choices=('Published', 'Draft'), required=True)
+        pub_date = DateTimeField()
+
+        def clean(self):
+            # Validate that only published essays have a `pub_date`
+            if self.status == 'Draft' and self.pub_date is not None:
+                raise ValidationError('Draft entries should not have a publication date.')
+            # Set the pub_date for published items if not set.
+            if self.status == 'Published' and self.pub_date is None:
+                self.pub_date = datetime.now()
+
+.. note::
+    Cleaning is only called if validation is turned on and when calling
+    :meth:`~mongoengine.Document.save`.
+
+* Adding custom Field classes
+
+We recommend as much as possible to use fields provided by MongoEngine. However, it is also possible
+to subclass a Field and encapsulate some validation by overriding the `validate` method
+
+.. code-block:: python
+
+    class AgeField(IntField):
+
+        def validate(self, value):
+            super(AgeField, self).validate(value)     # let IntField.validate run first
+            if value == 60:
+                self.error('60 is not allowed')
+
+    class Person(Document):
+        age = AgeField(min_value=0, max_value=99)
+
+    Person(age=20).save()   # passes
+    Person(age=1000).save() # raises ValidationError (Integer value is too large: ['age'])
+    Person(age=60).save()   # raises ValidationError (Person:None) (60 is not allowed: ['age'])
+
+
+.. note::
+
+   When overriding `validate`, use `self.error("your-custom-error")` instead of raising ValidationError explicitly,
+   it will provide a better context with the error message
+
+Skipping validation
+====================
+
+Although discouraged as it allows to violate fields constraints, if for some reason you need to disable
+the validation and cleaning of a document when you call :meth:`~mongoengine.document.Document.save`, you can use `.save(validate=False)`.
+
+.. code-block:: python
+
+    class Person(Document):
+        age = IntField(max_value=100)
+
+    Person(age=1000).save()    # raises ValidationError (Integer value is too large)
+
+    Person(age=1000).save(validate=False)
+    person = Person.objects.first()
+    assert person.age == 1000
+

docs/index.rst

@@ -7,7 +7,7 @@ MongoDB. To install it, simply run
 
 .. code-block:: console
 
-    $ pip install -U mongoengine
+    $ python -m pip install -U mongoengine
 
 :doc:`tutorial`
   A quick tutorial building a tumblelog to get you up and running with
@@ -91,4 +91,3 @@ Indices and tables
 * :ref:`genindex`
 * :ref:`modindex`
 * :ref:`search`
-

docs/requirements.txt

@@ -0,0 +1,3 @@
+pymongo>=3.11
+Sphinx==3.2.1
+sphinx-rtd-theme==0.5.0

docs/tutorial.rst

@@ -18,7 +18,7 @@ location --- running it locally will be easier, but if that is not an option
 then it may be run on a remote server. If you haven't installed MongoEngine,
 simply use pip to install it like so::
 
-    $ pip install mongoengine
+    $ python -m pip install mongoengine
 
 Before we can start using MongoEngine, we need to tell it how to connect to our
 instance of :program:`mongod`. For this we use the :func:`~mongoengine.connect`

docs/upgrade.rst

@@ -52,7 +52,7 @@ rename its occurrences.
 This release includes a major rehaul of MongoEngine's code quality and
 introduces a few breaking changes. It also touches many different parts of
 the package and although all the changes have been tested and scrutinized,
-you're encouraged to thorougly test the upgrade.
+you're encouraged to thoroughly test the upgrade.
 
 First breaking change involves renaming `ConnectionError` to `MongoEngineConnectionError`.
 If you import or catch this exception, you'll need to rename it in your code.
@@ -85,10 +85,10 @@ by default from now on.
 
 The 0.8.7 package on pypi was corrupted.  If upgrading from 0.8.7 to 0.9.0 please follow: ::
 
-    pip uninstall pymongo
+    python -m pip uninstall pymongo
-    pip uninstall mongoengine
+    python -m pip uninstall mongoengine
-    pip install pymongo==2.8
+    python -m pip install pymongo==2.8
-    pip install mongoengine
+    python -m pip install mongoengine
 
 0.8.7
 *****
@@ -153,7 +153,7 @@ inherited classes like so: ::
 
     # 4. Remove indexes
     info = collection.index_information()
-    indexes_to_drop = [key for key, value in info.iteritems()
+    indexes_to_drop = [key for key, value in info.items()
                        if '_types' in dict(value['key'])]
     for index in indexes_to_drop:
         collection.drop_index(index)

mongoengine/__init__.py

@@ -10,12 +10,12 @@ from mongoengine import signals
 # mongoengine, e.g. instead of `from mongoengine.connection import connect`,
 # users can simply use `from mongoengine import connect`, or even
 # `from mongoengine import *` and then `connect('testdb')`.
-from mongoengine.connection import *
+from mongoengine.connection import *  # noqa: F401
-from mongoengine.document import *
+from mongoengine.document import *  # noqa: F401
-from mongoengine.errors import *
+from mongoengine.errors import *  # noqa: F401
-from mongoengine.fields import *
+from mongoengine.fields import *  # noqa: F401
-from mongoengine.queryset import *
+from mongoengine.queryset import *  # noqa: F401
-from mongoengine.signals import *
+from mongoengine.signals import *  # noqa: F401
 
 
 __all__ = (
@@ -28,7 +28,7 @@ __all__ = (
 )
 
 
-VERSION = (0, 19, 1)
+VERSION = (0, 22, 0)
 
 
 def get_version():

mongoengine/base/datastructures.py

@@ -1,8 +1,6 @@
 import weakref
 
 from bson import DBRef
-import six
-from six import iteritems
 
 from mongoengine.common import _import_class
 from mongoengine.errors import DoesNotExist, MultipleObjectsReturned
@@ -53,7 +51,7 @@ class BaseDict(dict):
         if isinstance(instance, BaseDocument):
             self._instance = weakref.proxy(instance)
         self._name = name
-        super(BaseDict, self).__init__(dict_items)
+        super().__init__(dict_items)
 
     def get(self, key, default=None):
         # get does not use __getitem__ by default so we must override it as well
@@ -63,18 +61,18 @@ class BaseDict(dict):
             return default
 
     def __getitem__(self, key):
-        value = super(BaseDict, self).__getitem__(key)
+        value = super().__getitem__(key)
 
         EmbeddedDocument = _import_class("EmbeddedDocument")
         if isinstance(value, EmbeddedDocument) and value._instance is None:
             value._instance = self._instance
         elif isinstance(value, dict) and not isinstance(value, BaseDict):
-            value = BaseDict(value, None, "%s.%s" % (self._name, key))
+            value = BaseDict(value, None, f"{self._name}.{key}")
-            super(BaseDict, self).__setitem__(key, value)
+            super().__setitem__(key, value)
             value._instance = self._instance
         elif isinstance(value, list) and not isinstance(value, BaseList):
-            value = BaseList(value, None, "%s.%s" % (self._name, key))
+            value = BaseList(value, None, f"{self._name}.{key}")
-            super(BaseDict, self).__setitem__(key, value)
+            super().__setitem__(key, value)
             value._instance = self._instance
         return value
 
@@ -99,7 +97,7 @@ class BaseDict(dict):
     def _mark_as_changed(self, key=None):
         if hasattr(self._instance, "_mark_as_changed"):
             if key:
-                self._instance._mark_as_changed("%s.%s" % (self._name, key))
+                self._instance._mark_as_changed(f"{self._name}.{key}")
             else:
                 self._instance._mark_as_changed(self._name)
 
@@ -117,13 +115,13 @@ class BaseList(list):
         if isinstance(instance, BaseDocument):
             self._instance = weakref.proxy(instance)
         self._name = name
-        super(BaseList, self).__init__(list_items)
+        super().__init__(list_items)
 
     def __getitem__(self, key):
         # change index to positive value because MongoDB does not support negative one
         if isinstance(key, int) and key < 0:
             key = len(self) + key
-        value = super(BaseList, self).__getitem__(key)
+        value = super().__getitem__(key)
 
         if isinstance(key, slice):
             # When receiving a slice operator, we don't convert the structure and bind
@@ -135,19 +133,18 @@ class BaseList(list):
             value._instance = self._instance
         elif isinstance(value, dict) and not isinstance(value, BaseDict):
             # Replace dict by BaseDict
-            value = BaseDict(value, None, "%s.%s" % (self._name, key))
+            value = BaseDict(value, None, f"{self._name}.{key}")
-            super(BaseList, self).__setitem__(key, value)
+            super().__setitem__(key, value)
             value._instance = self._instance
         elif isinstance(value, list) and not isinstance(value, BaseList):
             # Replace list by BaseList
-            value = BaseList(value, None, "%s.%s" % (self._name, key))
+            value = BaseList(value, None, f"{self._name}.{key}")
-            super(BaseList, self).__setitem__(key, value)
+            super().__setitem__(key, value)
             value._instance = self._instance
         return value
 
     def __iter__(self):
-        for v in super(BaseList, self).__iter__():
+        yield from super().__iter__()
-            yield v
 
     def __getstate__(self):
         self.instance = None
@@ -165,7 +162,7 @@ class BaseList(list):
             # instead, we simply marks the whole list as changed
             changed_key = None
 
-        result = super(BaseList, self).__setitem__(key, value)
+        result = super().__setitem__(key, value)
         self._mark_as_changed(changed_key)
         return result
 
@@ -180,30 +177,17 @@ class BaseList(list):
     __iadd__ = mark_as_changed_wrapper(list.__iadd__)
     __imul__ = mark_as_changed_wrapper(list.__imul__)
 
-    if six.PY2:
-        # Under py3 __setslice__, __delslice__ and __getslice__
-        # are replaced by __setitem__, __delitem__ and __getitem__ with a slice as parameter
-        # so we mimic this under python 2
-        def __setslice__(self, i, j, sequence):
-            return self.__setitem__(slice(i, j), sequence)
-
-        def __delslice__(self, i, j):
-            return self.__delitem__(slice(i, j))
-
-        def __getslice__(self, i, j):
-            return self.__getitem__(slice(i, j))
-
     def _mark_as_changed(self, key=None):
         if hasattr(self._instance, "_mark_as_changed"):
-            if key:
+            if key is not None:
-                self._instance._mark_as_changed("%s.%s" % (self._name, key % len(self)))
+                self._instance._mark_as_changed(f"{self._name}.{key % len(self)}")
             else:
                 self._instance._mark_as_changed(self._name)
 
 
 class EmbeddedDocumentList(BaseList):
     def __init__(self, list_items, instance, name):
-        super(EmbeddedDocumentList, self).__init__(list_items, instance, name)
+        super().__init__(list_items, instance, name)
         self._instance = instance
 
     @classmethod
@@ -213,7 +197,7 @@ class EmbeddedDocumentList(BaseList):
         """
         for key, expected_value in kwargs.items():
             doc_val = getattr(embedded_doc, key)
-            if doc_val != expected_value and six.text_type(doc_val) != expected_value:
+            if doc_val != expected_value and str(doc_val) != expected_value:
                 return False
         return True
 
@@ -229,7 +213,7 @@ class EmbeddedDocumentList(BaseList):
         Filters the list by only including embedded documents with the
         given keyword arguments.
 
-        This method only supports simple comparison (e.g: .filter(name='John Doe'))
+        This method only supports simple comparison (e.g. .filter(name='John Doe'))
         and does not support operators like __gte, __lte, __icontains like queryset.filter does
 
         :param kwargs: The keyword arguments corresponding to the fields to
@@ -303,11 +287,11 @@ class EmbeddedDocumentList(BaseList):
 
     def create(self, **values):
         """
-        Creates a new embedded document and saves it to the database.
+        Creates a new instance of the EmbeddedDocument and appends it to this EmbeddedDocumentList.
 
         .. note::
-            The embedded document changes are not automatically saved
+            the instance of the EmbeddedDocument is not automatically saved to the database.
-            to the database after calling this method.
+            You still need to call .save() on the parent Document.
 
         :param values: A dictionary of values for the embedded document.
         :return: The new embedded document instance.
@@ -368,13 +352,13 @@ class EmbeddedDocumentList(BaseList):
         return len(values)
 
 
-class StrictDict(object):
+class StrictDict:
     __slots__ = ()
     _special_fields = {"get", "pop", "iteritems", "items", "keys", "create"}
     _classes = {}
 
     def __init__(self, **kwargs):
-        for k, v in iteritems(kwargs):
+        for k, v in kwargs.items():
             setattr(self, k, v)
 
     def __getitem__(self, key):
@@ -422,13 +406,13 @@ class StrictDict(object):
         return (key for key in self.__slots__ if hasattr(self, key))
 
     def __len__(self):
-        return len(list(iteritems(self)))
+        return len(list(self.items()))
 
     def __eq__(self, other):
-        return self.items() == other.items()
+        return list(self.items()) == list(other.items())
 
     def __ne__(self, other):
-        return self.items() != other.items()
+        return not (self == other)
 
     @classmethod
     def create(cls, allowed_keys):
@@ -443,7 +427,7 @@ class StrictDict(object):
 
                 def __repr__(self):
                     return "{%s}" % ", ".join(
-                        '"{0!s}": {1!r}'.format(k, v) for k, v in self.items()
+                        f'"{k!s}": {v!r}' for k, v in self.items()
                     )
 
             cls._classes[allowed_keys] = SpecificStrictDict
@@ -468,9 +452,7 @@ class LazyReference(DBRef):
         self.document_type = document_type
         self._cached_doc = cached_doc
         self.passthrough = passthrough
-        super(LazyReference, self).__init__(
+        super().__init__(self.document_type._get_collection_name(), pk)
-            self.document_type._get_collection_name(), pk
-        )
 
     def __getitem__(self, name):
         if not self.passthrough:
@@ -488,4 +470,4 @@ class LazyReference(DBRef):
             raise AttributeError()
 
     def __repr__(self):
-        return "<LazyReference(%s, %r)>" % (self.document_type, self.pk)
+        return f"<LazyReference({self.document_type}, {self.pk!r})>"

mongoengine/base/document.py

@@ -1,11 +1,10 @@
 import copy
+
 import numbers
 from functools import partial
 
 from bson import DBRef, ObjectId, SON, json_util
 import pymongo
-import six
-from six import iteritems
 
 from mongoengine import signals
 from mongoengine.base.common import get_document
@@ -25,14 +24,13 @@ from mongoengine.errors import (
     OperationError,
     ValidationError,
 )
-from mongoengine.python_support import Hashable
 
 __all__ = ("BaseDocument", "NON_FIELD_ERRORS")
 
 NON_FIELD_ERRORS = "__all__"
 
 
-class BaseDocument(object):
+class BaseDocument:
     # TODO simplify how `_changed_fields` is used.
     # Currently, handling of `_changed_fields` seems unnecessarily convoluted:
     # 1. `BaseDocument` defines `_changed_fields` in its `__slots__`, yet it's
@@ -66,8 +64,6 @@ class BaseDocument(object):
             It may contain additional reserved keywords, e.g. "__auto_convert".
         :param __auto_convert: If True, supplied values will be converted
             to Python-type values via each field's `to_python` method.
-        :param __only_fields: A set of fields that have been loaded for
-            this document. Empty if all fields have been loaded.
         :param _created: Indicates whether this is a brand new document
             or whether it's already been persisted before. Defaults to true.
         """
@@ -82,8 +78,6 @@ class BaseDocument(object):
 
         __auto_convert = values.pop("__auto_convert", True)
 
-        __only_fields = set(values.pop("__only_fields", values))
-
         _created = values.pop("_created", True)
 
         signals.pre_init.send(self.__class__, document=self, values=values)
@@ -92,12 +86,10 @@ class BaseDocument(object):
         # if so raise an Exception.
         if not self._dynamic and (self._meta.get("strict", True) or _created):
             _undefined_fields = set(values.keys()) - set(
-                self._fields.keys() + ["id", "pk", "_cls", "_text_score"]
+                list(self._fields.keys()) + ["id", "pk", "_cls", "_text_score"]
             )
             if _undefined_fields:
-                msg = ('The fields "{0}" do not exist on the document "{1}"').format(
+                msg = f'The fields "{_undefined_fields}" do not exist on the document "{self._class_name}"'
-                    _undefined_fields, self._class_name
-                )
                 raise FieldDoesNotExist(msg)
 
         if self.STRICT and not self._dynamic:
@@ -107,37 +99,32 @@ class BaseDocument(object):
 
         self._dynamic_fields = SON()
 
-        # Assign default values to the instance.
+        # Assign default values for fields
-        # We set default values only for fields loaded from DB. See
+        # not set in the constructor
-        # https://github.com/mongoengine/mongoengine/issues/399 for more info.
+        for field_name in self._fields:
-        for key, field in iteritems(self._fields):
+            if field_name in values:
-            if self._db_field_map.get(key, key) in __only_fields:
                 continue
-            value = getattr(self, key, None)
+            value = getattr(self, field_name, None)
-            setattr(self, key, value)
+            setattr(self, field_name, value)
 
         if "_cls" not in values:
             self._cls = self._class_name
 
-        # Set passed values after initialisation
+        # Set actual values
-        if self._dynamic:
+        dynamic_data = {}
-            dynamic_data = {}
+        FileField = _import_class("FileField")
-            for key, value in iteritems(values):
+        for key, value in values.items():
-                if key in self._fields or key == "_id":
+            field = self._fields.get(key)
-                    setattr(self, key, value)
+            if field or key in ("id", "pk", "_cls"):
-                else:
+                if __auto_convert and value is not None:
+                    if field and not isinstance(field, FileField):
+                        value = field.to_python(value)
+                setattr(self, key, value)
+            else:
+                if self._dynamic:
                     dynamic_data[key] = value
-        else:
-            FileField = _import_class("FileField")
-            for key, value in iteritems(values):
-                key = self._reverse_db_field_map.get(key, key)
-                if key in self._fields or key in ("id", "pk", "_cls"):
-                    if __auto_convert and value is not None:
-                        field = self._fields.get(key)
-                        if field and not isinstance(field, FileField):
-                            value = field.to_python(value)
-                    setattr(self, key, value)
                 else:
+                    # For strict Document
                     self._data[key] = value
 
         # Set any get_<field>_display methods
@@ -145,7 +132,7 @@ class BaseDocument(object):
 
         if self._dynamic:
             self._dynamic_lock = False
-            for key, value in iteritems(dynamic_data):
+            for key, value in dynamic_data.items():
                 setattr(self, key, value)
 
         # Flag initialised
@@ -163,7 +150,7 @@ class BaseDocument(object):
                 default = default()
             setattr(self, field_name, default)
         else:
-            super(BaseDocument, self).__delattr__(*args, **kwargs)
+            super().__delattr__(*args, **kwargs)
 
     def __setattr__(self, name, value):
         # Handle dynamic data only if an initialised dynamic document
@@ -210,9 +197,9 @@ class BaseDocument(object):
             and self__created
             and name == self._meta.get("id_field")
         ):
-            super(BaseDocument, self).__setattr__("_created", False)
+            super().__setattr__("_created", False)
 
-        super(BaseDocument, self).__setattr__(name, value)
+        super().__setattr__(name, value)
 
     def __getstate__(self):
         data = {}
@@ -242,10 +229,10 @@ class BaseDocument(object):
                 setattr(self, k, data[k])
         if "_fields_ordered" in data:
             if self._dynamic:
-                setattr(self, "_fields_ordered", data["_fields_ordered"])
+                self._fields_ordered = data["_fields_ordered"]
             else:
                 _super_fields_ordered = type(self)._fields_ordered
-                setattr(self, "_fields_ordered", _super_fields_ordered)
+                self._fields_ordered = _super_fields_ordered
 
         dynamic_fields = data.get("_dynamic_fields") or SON()
         for k in dynamic_fields.keys():
@@ -255,8 +242,7 @@ class BaseDocument(object):
         return iter(self._fields_ordered)
 
     def __getitem__(self, name):
-        """Dictionary-style field access, return a field's value if present.
+        """Dictionary-style field access, return a field's value if present."""
-        """
         try:
             if name in self._fields_ordered:
                 return getattr(self, name)
@@ -265,8 +251,7 @@ class BaseDocument(object):
         raise KeyError(name)
 
     def __setitem__(self, name, value):
-        """Dictionary-style field access, set a field's value.
+        """Dictionary-style field access, set a field's value."""
-        """
         # Ensure that the field exists before settings its value
         if not self._dynamic and name not in self._fields:
             raise KeyError(name)
@@ -288,16 +273,13 @@ class BaseDocument(object):
         except (UnicodeEncodeError, UnicodeDecodeError):
             u = "[Bad Unicode data]"
         repr_type = str if u is None else type(u)
-        return repr_type("<%s: %s>" % (self.__class__.__name__, u))
+        return repr_type(f"<{self.__class__.__name__}: {u}>")
 
     def __str__(self):
         # TODO this could be simpler?
         if hasattr(self, "__unicode__"):
-            if six.PY3:
+            return self.__unicode__()
-                return self.__unicode__()
+        return "%s object" % self.__class__.__name__
-            else:
-                return six.text_type(self).encode("utf-8")
-        return six.text_type("%s object" % self.__class__.__name__)
 
     def __eq__(self, other):
         if (
@@ -319,7 +301,8 @@ class BaseDocument(object):
 
     def clean(self):
         """
-        Hook for doing document level data cleaning before validation is run.
+        Hook for doing document level data cleaning (usually validation or assignment)
+        before validation is run.
 
         Any ValidationError raised by this method will not be associated with
         a particular field; it will have a special-case association with the
@@ -446,7 +429,7 @@ class BaseDocument(object):
                 pk = self.pk
             elif self._instance and hasattr(self._instance, "pk"):
                 pk = self._instance.pk
-            message = "ValidationError (%s:%s) " % (self._class_name, pk)
+            message = f"ValidationError ({self._class_name}:{pk}) "
             raise ValidationError(message, errors=errors)
 
     def to_json(self, *args, **kwargs):
@@ -519,7 +502,7 @@ class BaseDocument(object):
         if "." in key:
             key, rest = key.split(".", 1)
             key = self._db_field_map.get(key, key)
-            key = "%s.%s" % (key, rest)
+            key = f"{key}.{rest}"
         else:
             key = self._db_field_map.get(key, key)
 
@@ -542,6 +525,9 @@ class BaseDocument(object):
         """Using _get_changed_fields iterate and remove any fields that
         are marked as changed.
         """
+        ReferenceField = _import_class("ReferenceField")
+        GenericReferenceField = _import_class("GenericReferenceField")
+
         for changed in self._get_changed_fields():
             parts = changed.split(".")
             data = self
@@ -554,7 +540,8 @@ class BaseDocument(object):
                 elif isinstance(data, dict):
                     data = data.get(part, None)
                 else:
-                    data = getattr(data, part, None)
+                    field_name = data._reverse_db_field_map.get(part, part)
+                    data = getattr(data, field_name, None)
 
                 if not isinstance(data, LazyReference) and hasattr(
                     data, "_changed_fields"
@@ -563,10 +550,40 @@ class BaseDocument(object):
                         continue
 
                     data._changed_fields = []
+                elif isinstance(data, (list, tuple, dict)):
+                    if hasattr(data, "field") and isinstance(
+                        data.field, (ReferenceField, GenericReferenceField)
+                    ):
+                        continue
+                    BaseDocument._nestable_types_clear_changed_fields(data)
 
         self._changed_fields = []
 
-    def _nestable_types_changed_fields(self, changed_fields, base_key, data):
+    @staticmethod
+    def _nestable_types_clear_changed_fields(data):
+        """Inspect nested data for changed fields
+
+        :param data: data to inspect for changes
+        """
+        Document = _import_class("Document")
+
+        # Loop list / dict fields as they contain documents
+        # Determine the iterator to use
+        if not hasattr(data, "items"):
+            iterator = enumerate(data)
+        else:
+            iterator = data.items()
+
+        for _index_or_key, value in iterator:
+            if hasattr(value, "_get_changed_fields") and not isinstance(
+                value, Document
+            ):  # don't follow references
+                value._clear_changed_fields()
+            elif isinstance(value, (list, tuple, dict)):
+                BaseDocument._nestable_types_clear_changed_fields(value)
+
+    @staticmethod
+    def _nestable_types_changed_fields(changed_fields, base_key, data):
         """Inspect nested data for changed fields
 
         :param changed_fields: Previously collected changed fields
@@ -578,10 +595,10 @@ class BaseDocument(object):
         if not hasattr(data, "items"):
             iterator = enumerate(data)
         else:
-            iterator = iteritems(data)
+            iterator = data.items()
 
         for index_or_key, value in iterator:
-            item_key = "%s%s." % (base_key, index_or_key)
+            item_key = f"{base_key}{index_or_key}."
             # don't check anything lower if this key is already marked
             # as changed.
             if item_key[:-1] in changed_fields:
@@ -589,13 +606,14 @@ class BaseDocument(object):
 
             if hasattr(value, "_get_changed_fields"):
                 changed = value._get_changed_fields()
-                changed_fields += ["%s%s" % (item_key, k) for k in changed if k]
+                changed_fields += [f"{item_key}{k}" for k in changed if k]
             elif isinstance(value, (list, tuple, dict)):
-                self._nestable_types_changed_fields(changed_fields, item_key, value)
+                BaseDocument._nestable_types_changed_fields(
+                    changed_fields, item_key, value
+                )
 
     def _get_changed_fields(self):
-        """Return a list of all fields that have explicitly been changed.
+        """Return a list of all fields that have explicitly been changed."""
-        """
         EmbeddedDocument = _import_class("EmbeddedDocument")
         ReferenceField = _import_class("ReferenceField")
         GenericReferenceField = _import_class("GenericReferenceField")
@@ -620,7 +638,7 @@ class BaseDocument(object):
             if isinstance(data, EmbeddedDocument):
                 # Find all embedded fields that have been changed
                 changed = data._get_changed_fields()
-                changed_fields += ["%s%s" % (key, k) for k in changed if k]
+                changed_fields += [f"{key}{k}" for k in changed if k]
             elif isinstance(data, (list, tuple, dict)):
                 if hasattr(field, "field") and isinstance(
                     field.field, (ReferenceField, GenericReferenceField)
@@ -670,7 +688,7 @@ class BaseDocument(object):
                 del set_data["_id"]
 
         # Determine if any changed items were actually unset.
-        for path, value in set_data.items():
+        for path, value in list(set_data.items()):
             if value or isinstance(
                 value, (numbers.Number, bool)
             ):  # Account for 0 and True that are truthy
@@ -726,11 +744,8 @@ class BaseDocument(object):
         return cls._meta.get("collection", None)
 
     @classmethod
-    def _from_son(cls, son, _auto_dereference=True, only_fields=None, created=False):
+    def _from_son(cls, son, _auto_dereference=True, created=False):
-        """Create an instance of a Document (subclass) from a PyMongo SON."""
+        """Create an instance of a Document (subclass) from a PyMongo SON (dict)"""
-        if not only_fields:
-            only_fields = []
-
         if son and not isinstance(son, dict):
             raise ValueError(
                 "The source SON object needs to be of type 'dict' but a '%s' was found"
@@ -743,8 +758,10 @@ class BaseDocument(object):
 
         # Convert SON to a data dict, making sure each key is a string and
         # corresponds to the right db field.
+        # This is needed as _from_son is currently called both from BaseDocument.__init__
+        # and from EmbeddedDocumentField.to_python
         data = {}
-        for key, value in iteritems(son):
+        for key, value in son.items():
             key = str(key)
             key = cls._db_field_map.get(key, key)
             data[key] = value
@@ -759,7 +776,7 @@ class BaseDocument(object):
         if not _auto_dereference:
             fields = copy.deepcopy(fields)
 
-        for field_name, field in iteritems(fields):
+        for field_name, field in fields.items():
             field._auto_dereference = _auto_dereference
             if field.db_field in data:
                 value = data[field.db_field]
@@ -773,10 +790,8 @@ class BaseDocument(object):
                     errors_dict[field_name] = e
 
         if errors_dict:
-            errors = "\n".join(
+            errors = "\n".join([f"Field '{k}' - {v}" for k, v in errors_dict.items()])
-                ["Field '%s' - %s" % (k, v) for k, v in errors_dict.items()]
+            msg = "Invalid data to create a `{}` instance.\n{}".format(
-            )
-            msg = "Invalid data to create a `%s` instance.\n%s" % (
                 cls._class_name,
                 errors,
             )
@@ -784,11 +799,9 @@ class BaseDocument(object):
 
         # In STRICT documents, remove any keys that aren't in cls._fields
         if cls.STRICT:
-            data = {k: v for k, v in iteritems(data) if k in cls._fields}
+            data = {k: v for k, v in data.items() if k in cls._fields}
 
-        obj = cls(
+        obj = cls(__auto_convert=False, _created=created, **data)
-            __auto_convert=False, _created=created, __only_fields=only_fields, **data
-        )
         obj._changed_fields = []
         if not _auto_dereference:
             obj._fields = fields
@@ -831,7 +844,7 @@ class BaseDocument(object):
     @classmethod
     def _build_index_spec(cls, spec):
         """Build a PyMongo index spec from a MongoEngine index spec."""
-        if isinstance(spec, six.string_types):
+        if isinstance(spec, str):
             spec = {"fields": [spec]}
         elif isinstance(spec, (list, tuple)):
             spec = {"fields": list(spec)}
@@ -928,7 +941,7 @@ class BaseDocument(object):
 
                 # Add any unique_with fields to the back of the index spec
                 if field.unique_with:
-                    if isinstance(field.unique_with, six.string_types):
+                    if isinstance(field.unique_with, str):
                         field.unique_with = [field.unique_with]
 
                     # Convert unique_with field names to real field names
@@ -948,9 +961,7 @@ class BaseDocument(object):
                     unique_fields += unique_with
 
                 # Add the new index to the list
-                fields = [
+                fields = [(f"{namespace}{f}", pymongo.ASCENDING) for f in unique_fields]
-                    ("%s%s" % (namespace, f), pymongo.ASCENDING) for f in unique_fields
-                ]
                 index = {"fields": fields, "unique": True, "sparse": sparse}
                 unique_indexes.append(index)
 
@@ -986,9 +997,7 @@ class BaseDocument(object):
             "PolygonField",
         )
 
-        geo_field_types = tuple(
+        geo_field_types = tuple(_import_class(field) for field in geo_field_type_names)
-            [_import_class(field) for field in geo_field_type_names]
-        )
 
         for field in cls._fields.values():
             if not isinstance(field, geo_field_types):
@@ -1006,7 +1015,7 @@ class BaseDocument(object):
             elif field._geo_index:
                 field_name = field.db_field
                 if parent_field:
-                    field_name = "%s.%s" % (parent_field, field_name)
+                    field_name = f"{parent_field}.{field_name}"
                 geo_indices.append({"fields": [(field_name, field._geo_index)]})
 
         return geo_indices
@@ -1144,8 +1153,7 @@ class BaseDocument(object):
 
     @classmethod
     def _translate_field_name(cls, field, sep="."):
-        """Translate a field attribute name to a database field name.
+        """Translate a field attribute name to a database field name."""
-        """
         parts = field.split(sep)
         parts = [f.db_field for f in cls._lookup_field(parts)]
         return ".".join(parts)
@@ -1175,9 +1183,6 @@ class BaseDocument(object):
                 else [value]
             )
             return sep.join(
-                [
+                [str(dict(field.choices).get(val, val)) for val in values or []]
-                    six.text_type(dict(field.choices).get(val, val))
-                    for val in values or []
-                ]
             )
         return value

mongoengine/base/fields.py

@@ -1,11 +1,8 @@
 import operator
-import warnings
 import weakref
 
 from bson import DBRef, ObjectId, SON
 import pymongo
-import six
-from six import iteritems
 
 from mongoengine.base.common import UPDATE_OPERATORS
 from mongoengine.base.datastructures import BaseDict, BaseList, EmbeddedDocumentList
@@ -15,14 +12,12 @@ from mongoengine.errors import DeprecatedError, ValidationError
 __all__ = ("BaseField", "ComplexBaseField", "ObjectIdField", "GeoJsonBaseField")
 
 
-class BaseField(object):
+class BaseField:
     """A base class for fields in a MongoDB document. Instances of this class
     may be added to subclasses of `Document` to define a document's schema.
-
-    .. versionchanged:: 0.5 - added verbose and help text
     """
 
-    name = None
+    name = None  # set in TopLevelDocumentMetaclass
     _geo_index = False
     _auto_gen = False  # Call `generate` to generate a value
     _auto_dereference = True
@@ -36,7 +31,6 @@ class BaseField(object):
     def __init__(
         self,
         db_field=None,
-        name=None,
         required=False,
         default=None,
         unique=False,
@@ -46,12 +40,11 @@ class BaseField(object):
         choices=None,
         null=False,
         sparse=False,
-        **kwargs
+        **kwargs,
     ):
         """
         :param db_field: The database field to store this field in
             (defaults to the name of the field)
-        :param name: Deprecated - use db_field
         :param required: If the field is required. Whether it has to have a
             value or not. Defaults to False.
         :param default: (optional) The default value for this field if no value
@@ -75,11 +68,8 @@ class BaseField(object):
             existing attributes. Common metadata includes `verbose_name` and
             `help_text`.
         """
-        self.db_field = (db_field or name) if not primary_key else "_id"
+        self.db_field = db_field if not primary_key else "_id"
 
-        if name:
-            msg = 'Field\'s "name" attribute deprecated in favour of "db_field"'
-            warnings.warn(msg, DeprecationWarning)
         self.required = required or primary_key
         self.default = default
         self.unique = bool(unique or unique_with)
@@ -92,13 +82,11 @@ class BaseField(object):
         self._owner_document = None
 
         # Make sure db_field is a string (if it's explicitly defined).
-        if self.db_field is not None and not isinstance(
+        if self.db_field is not None and not isinstance(self.db_field, str):
-            self.db_field, six.string_types
-        ):
             raise TypeError("db_field should be a string.")
 
         # Make sure db_field doesn't contain any forbidden characters.
-        if isinstance(self.db_field, six.string_types) and (
+        if isinstance(self.db_field, str) and (
             "." in self.db_field
             or "\0" in self.db_field
             or self.db_field.startswith("$")
@@ -129,8 +117,7 @@ class BaseField(object):
             BaseField.creation_counter += 1
 
     def __get__(self, instance, owner):
-        """Descriptor for retrieving a value from a field in a document.
+        """Descriptor for retrieving a value from a field in a document."""
-        """
         if instance is None:
             # Document class being used rather than a document object
             return self
@@ -221,14 +208,12 @@ class BaseField(object):
         # Choices which are other types of Documents
         if isinstance(value, (Document, EmbeddedDocument)):
             if not any(isinstance(value, c) for c in choice_list):
-                self.error(
+                self.error("Value must be an instance of %s" % (choice_list))
-                    "Value must be an instance of %s" % (six.text_type(choice_list))
-                )
         # Choices which are types other than Documents
         else:
             values = value if isinstance(value, (list, tuple)) else [value]
             if len(set(values) - set(choice_list)):
-                self.error("Value must be one of %s" % six.text_type(choice_list))
+                self.error("Value must be one of %s" % str(choice_list))
 
     def _validate(self, value, **kwargs):
         # Check the Choices Constraint
@@ -276,11 +261,11 @@ class ComplexBaseField(BaseField):
     Allows for nesting of embedded documents inside complex types.
     Handles the lazy dereferencing of a queryset by lazily dereferencing all
     items in a list / dict rather than one at a time.
-
-    .. versionadded:: 0.5
     """
 
-    field = None
+    def __init__(self, field=None, **kwargs):
+        self.field = field
+        super().__init__(**kwargs)
 
     def __get__(self, instance, owner):
         """Descriptor to automatically dereference references."""
@@ -316,7 +301,7 @@ class ComplexBaseField(BaseField):
             if hasattr(instance._data[self.name], "_dereferenced"):
                 instance._data[self.name]._dereferenced = True
 
-        value = super(ComplexBaseField, self).__get__(instance, owner)
+        value = super().__get__(instance, owner)
 
         # Convert lists / values so we can watch for any changes on them
         if isinstance(value, (list, tuple)):
@@ -345,7 +330,7 @@ class ComplexBaseField(BaseField):
 
     def to_python(self, value):
         """Convert a MongoDB-compatible type to a Python type."""
-        if isinstance(value, six.string_types):
+        if isinstance(value, str):
             return value
 
         if hasattr(value, "to_python"):
@@ -399,7 +384,7 @@ class ComplexBaseField(BaseField):
         EmbeddedDocument = _import_class("EmbeddedDocument")
         GenericReferenceField = _import_class("GenericReferenceField")
 
-        if isinstance(value, six.string_types):
+        if isinstance(value, str):
             return value
 
         if hasattr(value, "to_mongo"):
@@ -423,11 +408,11 @@ class ComplexBaseField(BaseField):
         if self.field:
             value_dict = {
                 key: self.field._to_mongo_safe_call(item, use_db_field, fields)
-                for key, item in iteritems(value)
+                for key, item in value.items()
             }
         else:
             value_dict = {}
-            for k, v in iteritems(value):
+            for k, v in value.items():
                 if isinstance(v, Document):
                     # We need the id from the saved object to create the DBRef
                     if v.pk is None:
@@ -466,8 +451,8 @@ class ComplexBaseField(BaseField):
         """If field is provided ensure the value is valid."""
         errors = {}
         if self.field:
-            if hasattr(value, "iteritems") or hasattr(value, "items"):
+            if hasattr(value, "items"):
-                sequence = iteritems(value)
+                sequence = value.items()
             else:
                 sequence = enumerate(value)
             for k, v in sequence:
@@ -480,7 +465,7 @@ class ComplexBaseField(BaseField):
 
             if errors:
                 field_class = self.field.__class__.__name__
-                self.error("Invalid %s item (%s)" % (field_class, value), errors=errors)
+                self.error(f"Invalid {field_class} item ({value})", errors=errors)
         # Don't allow empty values if required
         if self.required and not value:
             self.error("Field is required and cannot be empty")
@@ -513,10 +498,9 @@ class ObjectIdField(BaseField):
     def to_mongo(self, value):
         if not isinstance(value, ObjectId):
             try:
-                return ObjectId(six.text_type(value))
+                return ObjectId(str(value))
             except Exception as e:
-                # e.message attribute has been deprecated since Python 2.6
+                self.error(str(e))
-                self.error(six.text_type(e))
         return value
 
     def prepare_query_value(self, op, value):
@@ -524,16 +508,13 @@ class ObjectIdField(BaseField):
 
     def validate(self, value):
         try:
-            ObjectId(six.text_type(value))
+            ObjectId(str(value))
         except Exception:
-            self.error("Invalid Object ID")
+            self.error("Invalid ObjectID")
 
 
 class GeoJsonBaseField(BaseField):
-    """A geo json field storing a geojson style object.
+    """A geo json field storing a geojson style object."""
-
-    .. versionadded:: 0.8
-    """
 
     _geo_index = pymongo.GEOSPHERE
     _type = "GeoBase"
@@ -546,14 +527,14 @@ class GeoJsonBaseField(BaseField):
         self._name = "%sField" % self._type
         if not auto_index:
             self._geo_index = False
-        super(GeoJsonBaseField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def validate(self, value):
         """Validate the GeoJson object based on its type."""
         if isinstance(value, dict):
             if set(value.keys()) == {"type", "coordinates"}:
                 if value["type"] != self._type:
-                    self.error('%s type must be "%s"' % (self._name, self._type))
+                    self.error(f'{self._name} type must be "{self._type}"')
                 return self.validate(value["coordinates"])
             else:
                 self.error(

mongoengine/base/metaclasses.py

@@ -1,9 +1,6 @@
 import itertools
 import warnings
 
-import six
-from six import iteritems, itervalues
-
 from mongoengine.base.common import _document_registry
 from mongoengine.base.fields import BaseField, ComplexBaseField, ObjectIdField
 from mongoengine.common import _import_class
@@ -25,7 +22,7 @@ class DocumentMetaclass(type):
     # TODO lower complexity of this method
     def __new__(mcs, name, bases, attrs):
         flattened_bases = mcs._get_bases(bases)
-        super_new = super(DocumentMetaclass, mcs).__new__
+        super_new = super().__new__
 
         # If a base class just call super
         metaclass = attrs.get("my_metaclass")
@@ -69,7 +66,7 @@ class DocumentMetaclass(type):
             # Standard object mixin - merge in any Fields
             if not hasattr(base, "_meta"):
                 base_fields = {}
-                for attr_name, attr_value in iteritems(base.__dict__):
+                for attr_name, attr_value in base.__dict__.items():
                     if not isinstance(attr_value, BaseField):
                         continue
                     attr_value.name = attr_name
@@ -81,7 +78,7 @@ class DocumentMetaclass(type):
 
         # Discover any document fields
         field_names = {}
-        for attr_name, attr_value in iteritems(attrs):
+        for attr_name, attr_value in attrs.items():
             if not isinstance(attr_value, BaseField):
                 continue
             attr_value.name = attr_name
@@ -111,9 +108,7 @@ class DocumentMetaclass(type):
 
         attrs["_fields_ordered"] = tuple(
             i[1]
-            for i in sorted(
+            for i in sorted((v.creation_counter, v.name) for v in doc_fields.values())
-                (v.creation_counter, v.name) for v in itervalues(doc_fields)
-            )
         )
 
         #
@@ -173,24 +168,8 @@ class DocumentMetaclass(type):
         # Add class to the _document_registry
         _document_registry[new_class._class_name] = new_class
 
-        # In Python 2, User-defined methods objects have special read-only
-        # attributes 'im_func' and 'im_self' which contain the function obj
-        # and class instance object respectively.  With Python 3 these special
-        # attributes have been replaced by __func__ and __self__.  The Blinker
-        # module continues to use im_func and im_self, so the code below
-        # copies __func__ into im_func and __self__ into im_self for
-        # classmethod objects in Document derived classes.
-        if six.PY3:
-            for val in new_class.__dict__.values():
-                if isinstance(val, classmethod):
-                    f = val.__get__(new_class)
-                    if hasattr(f, "__func__") and not hasattr(f, "im_func"):
-                        f.__dict__.update({"im_func": getattr(f, "__func__")})
-                    if hasattr(f, "__self__") and not hasattr(f, "im_self"):
-                        f.__dict__.update({"im_self": getattr(f, "__self__")})
-
         # Handle delete rules
-        for field in itervalues(new_class._fields):
+        for field in new_class._fields.values():
             f = field
             if f.owner_document is None:
                 f.owner_document = new_class
@@ -252,8 +231,7 @@ class DocumentMetaclass(type):
             if base is object:
                 continue
             yield base
-            for child_base in mcs.__get_bases(base.__bases__):
+            yield from mcs.__get_bases(base.__bases__)
-                yield child_base
 
     @classmethod
     def _import_classes(mcs):
@@ -271,7 +249,7 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
 
     def __new__(mcs, name, bases, attrs):
         flattened_bases = mcs._get_bases(bases)
-        super_new = super(TopLevelDocumentMetaclass, mcs).__new__
+        super_new = super().__new__
 
         # Set default _meta data if base class, otherwise get user defined meta
         if attrs.get("my_metaclass") == TopLevelDocumentMetaclass:
@@ -284,7 +262,6 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
                 "indexes": [],  # indexes to be ensured at runtime
                 "id_field": None,
                 "index_background": False,
-                "index_drop_dups": False,
                 "index_opts": None,
                 "delete_rules": None,
                 # allow_inheritance can be True, False, and None. True means
@@ -360,7 +337,7 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
         # allow_inheritance to False. If the base Document allows inheritance,
         # none of its subclasses can override allow_inheritance to False.
         simple_class = all(
-            [b._meta.get("abstract") for b in flattened_bases if hasattr(b, "_meta")]
+            b._meta.get("abstract") for b in flattened_bases if hasattr(b, "_meta")
         )
         if (
             not simple_class
@@ -399,7 +376,7 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
             new_class.objects = QuerySetManager()
 
         # Validate the fields and set primary key if needed
-        for field_name, field in iteritems(new_class._fields):
+        for field_name, field in new_class._fields.items():
             if field.primary_key:
                 # Ensure only one primary key is set
                 current_pk = new_class._meta.get("id_field")
@@ -462,8 +439,8 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
 
         id_basename, id_db_basename, i = ("auto_id", "_auto_id", 0)
         for i in itertools.count():
-            id_name = "{0}_{1}".format(id_basename, i)
+            id_name = f"{id_basename}_{i}"
-            id_db_name = "{0}_{1}".format(id_db_basename, i)
+            id_db_name = f"{id_db_basename}_{i}"
             if id_name not in existing_fields and id_db_name not in existing_db_fields:
                 return id_name, id_db_name
 
@@ -476,7 +453,7 @@ class MetaDict(dict):
     _merge_options = ("indexes",)
 
     def merge(self, new_options):
-        for k, v in iteritems(new_options):
+        for k, v in new_options.items():
             if k in self._merge_options:
                 self[k] = self.get(k, []) + v
             else:

mongoengine/base/utils.py

@@ -1,7 +1,7 @@
 import re
 
 
-class LazyRegexCompiler(object):
+class LazyRegexCompiler:
     """Descriptor to allow lazy compilation of regex"""
 
     def __init__(self, pattern, flags=0):

mongoengine/connection.py

@@ -1,6 +1,5 @@
 from pymongo import MongoClient, ReadPreference, uri_parser
 from pymongo.database import _check_name
-import six
 
 __all__ = [
     "DEFAULT_CONNECTION_NAME",
@@ -39,8 +38,8 @@ def _check_db_name(name):
     """Check if a database name is valid.
     This functionality is copied from pymongo Database class constructor.
     """
-    if not isinstance(name, six.string_types):
+    if not isinstance(name, str):
-        raise TypeError("name must be an instance of %s" % six.string_types)
+        raise TypeError("name must be an instance of %s" % str)
     elif name != "$external":
         _check_name(name)
 
@@ -55,7 +54,7 @@ def _get_connection_settings(
     password=None,
     authentication_source=None,
     authentication_mechanism=None,
-    **kwargs
+    **kwargs,
 ):
     """Get the connection settings as a dict
 
@@ -75,8 +74,6 @@ def _get_connection_settings(
     : param kwargs: ad-hoc parameters to be passed into the pymongo driver,
         for example maxpoolsize, tz_aware, etc. See the documentation
         for pymongo's `MongoClient` for a full list.
-
-    .. versionchanged:: 0.10.6 - added mongomock support
     """
     conn_settings = {
         "name": name or db or DEFAULT_DATABASE_NAME,
@@ -93,7 +90,7 @@ def _get_connection_settings(
     conn_host = conn_settings["host"]
 
     # Host can be a list or a string, so if string, force to a list.
-    if isinstance(conn_host, six.string_types):
+    if isinstance(conn_host, str):
         conn_host = [conn_host]
 
     resolved_hosts = []
@@ -148,7 +145,7 @@ def _get_connection_settings(
                 # TODO simplify the code below once we drop support for
                 # PyMongo v3.4.
                 read_pf_mode = uri_options["readpreference"]
-                if isinstance(read_pf_mode, six.string_types):
+                if isinstance(read_pf_mode, str):
                     read_pf_mode = read_pf_mode.lower()
                 for preference in read_preferences:
                     if (
@@ -180,7 +177,7 @@ def register_connection(
     password=None,
     authentication_source=None,
     authentication_mechanism=None,
-    **kwargs
+    **kwargs,
 ):
     """Register the connection settings.
 
@@ -202,8 +199,6 @@ def register_connection(
     : param kwargs: ad-hoc parameters to be passed into the pymongo driver,
         for example maxpoolsize, tz_aware, etc. See the documentation
         for pymongo's `MongoClient` for a full list.
-
-    .. versionchanged:: 0.10.6 - added mongomock support
     """
     conn_settings = _get_connection_settings(
         db=db,
@@ -215,7 +210,7 @@ def register_connection(
         password=password,
         authentication_source=authentication_source,
         authentication_mechanism=authentication_mechanism,
-        **kwargs
+        **kwargs,
     )
     _connection_settings[alias] = conn_settings
 
@@ -318,7 +313,7 @@ def _create_connection(alias, connection_class, **connection_settings):
     try:
         return connection_class(**connection_settings)
     except Exception as e:
-        raise ConnectionFailure("Cannot connect to database %s :\n%s" % (alias, e))
+        raise ConnectionFailure(f"Cannot connect to database {alias} :\n{e}")
 
 
 def _find_existing_connection(connection_settings):
@@ -387,8 +382,6 @@ def connect(db=None, alias=DEFAULT_CONNECTION_NAME, **kwargs):
 
     See the docstring for `register_connection` for more details about all
     supported kwargs.
-
-    .. versionchanged:: 0.6 - added multiple database support.
     """
     if alias in _connections:
         prev_conn_setting = _connection_settings[alias]
@@ -396,8 +389,8 @@ def connect(db=None, alias=DEFAULT_CONNECTION_NAME, **kwargs):
 
         if new_conn_settings != prev_conn_setting:
             err_msg = (
-                u"A different connection with alias `{}` was already "
+                "A different connection with alias `{}` was already "
-                u"registered. Use disconnect() first"
+                "registered. Use disconnect() first"
             ).format(alias)
             raise ConnectionFailure(err_msg)
     else:

mongoengine/context_managers.py

@@ -1,7 +1,7 @@
 from contextlib import contextmanager
 
+from pymongo.read_concern import ReadConcern
 from pymongo.write_concern import WriteConcern
-from six import iteritems
 
 from mongoengine.common import _import_class
 from mongoengine.connection import DEFAULT_CONNECTION_NAME, get_db
@@ -14,10 +14,11 @@ __all__ = (
     "no_sub_classes",
     "query_counter",
     "set_write_concern",
+    "set_read_write_concern",
 )
 
 
-class switch_db(object):
+class switch_db:
     """switch_db alias context manager.
 
     Example ::
@@ -58,7 +59,7 @@ class switch_db(object):
         self.cls._collection = self.collection
 
 
-class switch_collection(object):
+class switch_collection:
     """switch_collection alias context manager.
 
     Example ::
@@ -100,7 +101,7 @@ class switch_collection(object):
         self.cls._get_collection_name = self.ori_get_collection_name
 
 
-class no_dereference(object):
+class no_dereference:
     """no_dereference context manager.
 
     Turns off all dereferencing in Documents for the duration of the context
@@ -123,7 +124,7 @@ class no_dereference(object):
 
         self.deref_fields = [
             k
-            for k, v in iteritems(self.cls._fields)
+            for k, v in self.cls._fields.items()
             if isinstance(v, (ReferenceField, GenericReferenceField, ComplexBaseField))
         ]
 
@@ -140,7 +141,7 @@ class no_dereference(object):
         return self.cls
 
 
-class no_sub_classes(object):
+class no_sub_classes:
     """no_sub_classes context manager.
 
     Only returns instances of this class and no sub (inherited) classes::
@@ -168,7 +169,7 @@ class no_sub_classes(object):
         self.cls._subclasses = self.cls_initial_subclasses
 
 
-class query_counter(object):
+class query_counter:
     """Query_counter context manager to get the number of queries.
     This works by updating the `profiling_level` of the database so that all queries get logged,
     resetting the db.system.profile collection at the beginning of the context and counting the new entries.
@@ -183,8 +184,7 @@ class query_counter(object):
     """
 
     def __init__(self, alias=DEFAULT_CONNECTION_NAME):
-        """Construct the query_counter
+        """Construct the query_counter"""
-        """
         self.db = get_db(alias=alias)
         self.initial_profiling_level = None
         self._ctx_query_counter = 0  # number of queries issued by the context
@@ -235,7 +235,7 @@ class query_counter(object):
 
     def __repr__(self):
         """repr query_counter as the number of queries."""
-        return u"%s" % self._get_count()
+        return "%s" % self._get_count()
 
     def _get_count(self):
         """Get the number of queries by counting the current number of entries in db.system.profile
@@ -257,3 +257,21 @@ def set_write_concern(collection, write_concerns):
     combined_concerns = dict(collection.write_concern.document.items())
     combined_concerns.update(write_concerns)
     yield collection.with_options(write_concern=WriteConcern(**combined_concerns))
+
+
+@contextmanager
+def set_read_write_concern(collection, write_concerns, read_concerns):
+    combined_write_concerns = dict(collection.write_concern.document.items())
+
+    if write_concerns is not None:
+        combined_write_concerns.update(write_concerns)
+
+    combined_read_concerns = dict(collection.read_concern.document.items())
+
+    if read_concerns is not None:
+        combined_read_concerns.update(read_concerns)
+
+    yield collection.with_options(
+        write_concern=WriteConcern(**combined_write_concerns),
+        read_concern=ReadConcern(**combined_read_concerns),
+    )

mongoengine/dereference.py

@@ -1,6 +1,4 @@
 from bson import DBRef, SON
-import six
-from six import iteritems
 
 from mongoengine.base import (
     BaseDict,
@@ -16,7 +14,7 @@ from mongoengine.fields import DictField, ListField, MapField, ReferenceField
 from mongoengine.queryset import QuerySet
 
 
-class DeReference(object):
+class DeReference:
     def __call__(self, items, max_depth=1, instance=None, name=None):
         """
         Cheaply dereferences the items to a set depth.
@@ -30,7 +28,7 @@ class DeReference(object):
             :class:`~mongoengine.base.ComplexBaseField`
         :param get: A boolean determining if being called by __get__
         """
-        if items is None or isinstance(items, six.string_types):
+        if items is None or isinstance(items, str):
             return items
 
         # cheapest way to convert a queryset to a list
@@ -53,10 +51,10 @@ class DeReference(object):
                 doc_type = doc_type.document_type
                 is_list = not hasattr(items, "items")
 
-                if is_list and all([i.__class__ == doc_type for i in items]):
+                if is_list and all(i.__class__ == doc_type for i in items):
                     return items
                 elif not is_list and all(
-                    [i.__class__ == doc_type for i in items.values()]
+                    i.__class__ == doc_type for i in items.values()
                 ):
                     return items
                 elif not field.dbref:
@@ -79,7 +77,7 @@ class DeReference(object):
 
                     def _get_items_from_dict(items):
                         new_items = {}
-                        for k, v in iteritems(items):
+                        for k, v in items.items():
                             value = v
                             if isinstance(v, list):
                                 value = _get_items_from_list(v)
@@ -120,7 +118,7 @@ class DeReference(object):
         depth += 1
         for item in iterator:
             if isinstance(item, (Document, EmbeddedDocument)):
-                for field_name, field in iteritems(item._fields):
+                for field_name, field in item._fields.items():
                     v = item._data.get(field_name, None)
                     if isinstance(v, LazyReference):
                         # LazyReference inherits DBRef but should not be dereferenced here !
@@ -136,7 +134,7 @@ class DeReference(object):
                             getattr(field, "field", None), "document_type", None
                         )
                         references = self._find_references(v, depth)
-                        for key, refs in iteritems(references):
+                        for key, refs in references.items():
                             if isinstance(
                                 field_cls, (Document, TopLevelDocumentMetaclass)
                             ):
@@ -153,16 +151,15 @@ class DeReference(object):
                 )
             elif isinstance(item, (dict, list, tuple)) and depth - 1 <= self.max_depth:
                 references = self._find_references(item, depth - 1)
-                for key, refs in iteritems(references):
+                for key, refs in references.items():
                     reference_map.setdefault(key, set()).update(refs)
 
         return reference_map
 
     def _fetch_objects(self, doc_type=None):
-        """Fetch all references and convert to their document objects
+        """Fetch all references and convert to their document objects"""
-        """
         object_map = {}
-        for collection, dbrefs in iteritems(self.reference_map):
+        for collection, dbrefs in self.reference_map.items():
 
             # we use getattr instead of hasattr because hasattr swallows any exception under python2
             # so it could hide nasty things without raising exceptions (cfr bug #1688))
@@ -174,7 +171,7 @@ class DeReference(object):
                     dbref for dbref in dbrefs if (col_name, dbref) not in object_map
                 ]
                 references = collection.objects.in_bulk(refs)
-                for key, doc in iteritems(references):
+                for key, doc in references.items():
                     object_map[(col_name, key)] = doc
             else:  # Generic reference: use the refs data to convert to document
                 if isinstance(doc_type, (ListField, DictField, MapField)):
@@ -250,7 +247,7 @@ class DeReference(object):
             data = []
         else:
             is_list = False
-            iterator = iteritems(items)
+            iterator = items.items()
             data = {}
 
         depth += 1
@@ -274,14 +271,12 @@ class DeReference(object):
                             (v["_ref"].collection, v["_ref"].id), v
                         )
                     elif isinstance(v, (dict, list, tuple)) and depth <= self.max_depth:
-                        item_name = six.text_type("{0}.{1}.{2}").format(
+                        item_name = f"{name}.{k}.{field_name}"
-                            name, k, field_name
-                        )
                         data[k]._data[field_name] = self._attach_objects(
                             v, depth, instance=instance, name=item_name
                         )
             elif isinstance(v, (dict, list, tuple)) and depth <= self.max_depth:
-                item_name = "%s.%s" % (name, k) if name else name
+                item_name = f"{name}.{k}" if name else name
                 data[k] = self._attach_objects(
                     v, depth - 1, instance=instance, name=item_name
                 )

mongoengine/document.py

@@ -1,11 +1,8 @@
 import re
-import warnings
 
 from bson.dbref import DBRef
 import pymongo
 from pymongo.read_preferences import ReadPreference
-import six
-from six import iteritems
 
 from mongoengine import signals
 from mongoengine.base import (
@@ -44,7 +41,7 @@ def includes_cls(fields):
     """Helper function used for ensuring and comparing indexes."""
     first_field = None
     if len(fields):
-        if isinstance(fields[0], six.string_types):
+        if isinstance(fields[0], str):
             first_field = fields[0]
         elif isinstance(fields[0], (list, tuple)) and len(fields[0]):
             first_field = fields[0][0]
@@ -55,8 +52,8 @@ class InvalidCollectionError(Exception):
     pass
 
 
-class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
+class EmbeddedDocument(BaseDocument, metaclass=DocumentMetaclass):
-    """A :class:`~mongoengine.Document` that isn't stored in its own
+    r"""A :class:`~mongoengine.Document` that isn't stored in its own
     collection.  :class:`~mongoengine.EmbeddedDocument`\ s should be used as
     fields on :class:`~mongoengine.Document`\ s through the
     :class:`~mongoengine.EmbeddedDocumentField` field type.
@@ -71,7 +68,6 @@ class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
 
     __slots__ = ("_instance",)
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass
 
@@ -82,7 +78,7 @@ class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
     __hash__ = None
 
     def __init__(self, *args, **kwargs):
-        super(EmbeddedDocument, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
         self._instance = None
         self._changed_fields = []
 
@@ -95,7 +91,7 @@ class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
         return not self.__eq__(other)
 
     def to_mongo(self, *args, **kwargs):
-        data = super(EmbeddedDocument, self).to_mongo(*args, **kwargs)
+        data = super().to_mongo(*args, **kwargs)
 
         # remove _id from the SON if it's in it and it's None
         if "_id" in data and data["_id"] is None:
@@ -104,7 +100,7 @@ class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
         return data
 
 
-class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
+class Document(BaseDocument, metaclass=TopLevelDocumentMetaclass):
     """The base class used for defining the structure and properties of
     collections of documents stored in MongoDB. Inherit from this class, and
     add fields as class attributes to define a document's structure.
@@ -156,7 +152,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
     in the :attr:`meta` dictionary.
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
 
@@ -260,7 +255,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
         return db.create_collection(collection_name, **opts)
 
     def to_mongo(self, *args, **kwargs):
-        data = super(Document, self).to_mongo(*args, **kwargs)
+        data = super().to_mongo(*args, **kwargs)
 
         # If '_id' is None, try and set it from self._data. If that
         # doesn't exist either, remove '_id' from the SON completely.
@@ -332,7 +327,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
     ):
         """Save the :class:`~mongoengine.Document` to the database. If the
         document already exists, it will be updated, otherwise it will be
-        created.
+        created. Returns the saved object instance.
 
         :param force_insert: only try to create a new document, don't allow
             updates of existing documents.
@@ -371,15 +366,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             meta['cascade'] = True.  Also you can pass different kwargs to
             the cascade save using cascade_kwargs which overwrites the
             existing kwargs with custom values.
-        .. versionchanged:: 0.8.5
-            Optional save_condition that only overwrites existing documents
-            if the condition is satisfied in the current db record.
-        .. versionchanged:: 0.10
-            :class:`OperationError` exception raised if save_condition fails.
-        .. versionchanged:: 0.10.1
-            :class: save_condition failure now raises a `SaveConditionError`
-        .. versionchanged:: 0.10.7
-            Add signal_kwargs argument
         """
         signal_kwargs = signal_kwargs or {}
 
@@ -431,16 +417,16 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
                 self.cascade_save(**kwargs)
 
         except pymongo.errors.DuplicateKeyError as err:
-            message = u"Tried to save duplicate unique keys (%s)"
+            message = "Tried to save duplicate unique keys (%s)"
-            raise NotUniqueError(message % six.text_type(err))
+            raise NotUniqueError(message % err)
         except pymongo.errors.OperationFailure as err:
             message = "Could not save document (%s)"
-            if re.match("^E1100[01] duplicate key", six.text_type(err)):
+            if re.match("^E1100[01] duplicate key", str(err)):
                 # E11000 - duplicate key error index
                 # E11001 - duplicate key on update
-                message = u"Tried to save duplicate unique keys (%s)"
+                message = "Tried to save duplicate unique keys (%s)"
-                raise NotUniqueError(message % six.text_type(err))
+                raise NotUniqueError(message % err)
-            raise OperationError(message % six.text_type(err))
+            raise OperationError(message % err)
 
         # Make sure we store the PK on this document now that it's saved
         id_field = self._meta["id_field"]
@@ -468,9 +454,9 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             # insert_one will provoke UniqueError alongside save does not
             # therefore, it need to catch and call replace_one.
             if "_id" in doc:
-                raw_object = wc_collection.find_one_and_replace(
+                select_dict = {"_id": doc["_id"]}
-                    {"_id": doc["_id"]}, doc
+                select_dict = self._integrate_shard_key(doc, select_dict)
-                )
+                raw_object = wc_collection.find_one_and_replace(select_dict, doc)
                 if raw_object:
                     return doc["_id"]
 
@@ -493,6 +479,23 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
 
         return update_doc
 
+    def _integrate_shard_key(self, doc, select_dict):
+        """Integrates the collection's shard key to the `select_dict`, which will be used for the query.
+        The value from the shard key is taken from the `doc` and finally the select_dict is returned.
+        """
+
+        # Need to add shard key to query, or you get an error
+        shard_key = self._meta.get("shard_key", tuple())
+        for k in shard_key:
+            path = self._lookup_field(k.split("."))
+            actual_key = [p.db_field for p in path]
+            val = doc
+            for ak in actual_key:
+                val = val[ak]
+            select_dict[".".join(actual_key)] = val
+
+        return select_dict
+
     def _save_update(self, doc, save_condition, write_concern):
         """Update an existing document.
 
@@ -508,15 +511,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
 
         select_dict["_id"] = object_id
 
-        # Need to add shard key to query, or you get an error
+        select_dict = self._integrate_shard_key(doc, select_dict)
-        shard_key = self._meta.get("shard_key", tuple())
-        for k in shard_key:
-            path = self._lookup_field(k.split("."))
-            actual_key = [p.db_field for p in path]
-            val = doc
-            for ak in actual_key:
-                val = val[ak]
-            select_dict[".".join(actual_key)] = val
 
         update_doc = self._get_update_doc()
         if update_doc:
@@ -559,7 +554,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             if not getattr(ref, "_changed_fields", True):
                 continue
 
-            ref_id = "%s,%s" % (ref.__class__.__name__, str(ref._data))
+            ref_id = "{},{}".format(ref.__class__.__name__, str(ref._data))
             if ref and ref_id not in _refs:
                 _refs.append(ref_id)
                 kwargs["_refs"] = _refs
@@ -625,16 +620,13 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             For example, ``save(..., w: 2, fsync: True)`` will
             wait until at least two servers have recorded the write and
             will force an fsync on the primary server.
-
-        .. versionchanged:: 0.10.7
-            Add signal_kwargs argument
         """
         signal_kwargs = signal_kwargs or {}
         signals.pre_delete.send(self.__class__, document=self, **signal_kwargs)
 
         # Delete FileFields separately
         FileField = _import_class("FileField")
-        for name, field in iteritems(self._fields):
+        for name, field in self._fields.items():
             if isinstance(field, FileField):
                 getattr(self, name).delete()
 
@@ -643,7 +635,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
                 write_concern=write_concern, _from_doc_delete=True
             )
         except pymongo.errors.OperationFailure as err:
-            message = u"Could not delete document (%s)" % err.message
+            message = "Could not delete document (%s)" % err.args
             raise OperationError(message)
         signals.post_delete.send(self.__class__, document=self, **signal_kwargs)
 
@@ -709,8 +701,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
     def select_related(self, max_depth=1):
         """Handles dereferencing of :class:`~bson.dbref.DBRef` objects to
         a maximum depth in order to cut down the number queries to mongodb.
-
-        .. versionadded:: 0.5
         """
         DeReference = _import_class("DeReference")
         DeReference()([self], max_depth + 1)
@@ -721,10 +711,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
 
         :param fields: (optional) args list of fields to reload
         :param max_depth: (optional) depth of dereferencing to follow
-
-        .. versionadded:: 0.1.2
-        .. versionchanged:: 0.6  Now chainable
-        .. versionchanged:: 0.9  Can provide specific fields to reload
         """
         max_depth = 1
         if fields and isinstance(fields[0], int):
@@ -826,9 +812,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
 
         Raises :class:`OperationError` if the document has no collection set
         (i.g. if it is `abstract`)
-
-        .. versionchanged:: 0.10.7
-            :class:`OperationError` exception raised if no collection available
         """
         coll_name = cls._get_collection_name()
         if not coll_name:
@@ -851,17 +834,13 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
         index_spec = cls._build_index_spec(keys)
         index_spec = index_spec.copy()
         fields = index_spec.pop("fields")
-        drop_dups = kwargs.get("drop_dups", False)
-        if drop_dups:
-            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
-            warnings.warn(msg, DeprecationWarning)
         index_spec["background"] = background
         index_spec.update(kwargs)
 
         return cls._get_collection().create_index(fields, **index_spec)
 
     @classmethod
-    def ensure_index(cls, key_or_list, drop_dups=False, background=False, **kwargs):
+    def ensure_index(cls, key_or_list, background=False, **kwargs):
         """Ensure that the given indexes are in place. Deprecated in favour
         of create_index.
 
@@ -869,12 +848,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             construct a multi-field index); keys may be prefixed with a **+**
             or a **-** to determine the index ordering
         :param background: Allows index creation in the background
-        :param drop_dups: Was removed/ignored with MongoDB >2.7.5. The value
-            will be removed if PyMongo3+ is used
         """
-        if drop_dups:
-            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
-            warnings.warn(msg, DeprecationWarning)
         return cls.create_index(key_or_list, background=background, **kwargs)
 
     @classmethod
@@ -887,12 +861,8 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
                   `auto_create_index` to False in the documents meta data
         """
         background = cls._meta.get("index_background", False)
-        drop_dups = cls._meta.get("index_drop_dups", False)
         index_opts = cls._meta.get("index_opts") or {}
         index_cls = cls._meta.get("index_cls", True)
-        if drop_dups:
-            msg = "drop_dups is deprecated and is removed when using PyMongo 3+."
-            warnings.warn(msg, DeprecationWarning)
 
         collection = cls._get_collection()
         # 746: when connection is via mongos, the read preference is not necessarily an indication that
@@ -936,7 +906,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
 
     @classmethod
     def list_indexes(cls):
-        """ Lists all of the indexes that should be created for given
+        """Lists all of the indexes that should be created for given
         collection. It includes all the indexes from super- and sub-classes.
         """
         if cls._meta.get("abstract"):
@@ -992,16 +962,16 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
                     indexes.append(index)
 
         # finish up by appending { '_id': 1 } and { '_cls': 1 }, if needed
-        if [(u"_id", 1)] not in indexes:
+        if [("_id", 1)] not in indexes:
-            indexes.append([(u"_id", 1)])
+            indexes.append([("_id", 1)])
         if cls._meta.get("index_cls", True) and cls._meta.get("allow_inheritance"):
-            indexes.append([(u"_cls", 1)])
+            indexes.append([("_cls", 1)])
 
         return indexes
 
     @classmethod
     def compare_indexes(cls):
-        """ Compares the indexes defined in MongoEngine with the ones
+        """Compares the indexes defined in MongoEngine with the ones
         existing in the database. Returns any missing/extra indexes.
         """
 
@@ -1019,19 +989,19 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
         extra = [index for index in existing if index not in required]
 
         # if { _cls: 1 } is missing, make sure it's *really* necessary
-        if [(u"_cls", 1)] in missing:
+        if [("_cls", 1)] in missing:
             cls_obsolete = False
             for index in existing:
                 if includes_cls(index) and index not in extra:
                     cls_obsolete = True
                     break
             if cls_obsolete:
-                missing.remove([(u"_cls", 1)])
+                missing.remove([("_cls", 1)])
 
         return {"missing": missing, "extra": extra}
 
 
-class DynamicDocument(six.with_metaclass(TopLevelDocumentMetaclass, Document)):
+class DynamicDocument(Document, metaclass=TopLevelDocumentMetaclass):
     """A Dynamic Document class allowing flexible, expandable and uncontrolled
     schemas.  As a :class:`~mongoengine.Document` subclass, acts in the same
     way as an ordinary document but has expanded style properties.  Any data
@@ -1045,7 +1015,6 @@ class DynamicDocument(six.with_metaclass(TopLevelDocumentMetaclass, Document)):
         There is one caveat on Dynamic Documents: undeclared fields cannot start with `_`
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
 
@@ -1060,16 +1029,15 @@ class DynamicDocument(six.with_metaclass(TopLevelDocumentMetaclass, Document)):
             setattr(self, field_name, None)
             self._dynamic_fields[field_name].null = False
         else:
-            super(DynamicDocument, self).__delattr__(*args, **kwargs)
+            super().__delattr__(*args, **kwargs)
 
 
-class DynamicEmbeddedDocument(six.with_metaclass(DocumentMetaclass, EmbeddedDocument)):
+class DynamicEmbeddedDocument(EmbeddedDocument, metaclass=DocumentMetaclass):
     """A Dynamic Embedded Document class allowing flexible, expandable and
     uncontrolled schemas. See :class:`~mongoengine.DynamicDocument` for more
     information about dynamic documents.
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass
 
@@ -1089,7 +1057,7 @@ class DynamicEmbeddedDocument(six.with_metaclass(DocumentMetaclass, EmbeddedDocu
             setattr(self, field_name, None)
 
 
-class MapReduceDocument(object):
+class MapReduceDocument:
     """A document returned from a map/reduce query.
 
     :param collection: An instance of :class:`~pymongo.Collection`
@@ -1098,8 +1066,6 @@ class MapReduceDocument(object):
                 an ``ObjectId`` found in the given ``collection``,
                 the object can be accessed via the ``object`` property.
     :param value: The result(s) for this key.
-
-    .. versionadded:: 0.3
     """
 
     def __init__(self, document, collection, key, value):

mongoengine/errors.py

@@ -1,7 +1,5 @@
 from collections import defaultdict
 
-import six
-from six import iteritems
 
 __all__ = (
     "NotRegistered",
@@ -87,24 +85,24 @@ class ValidationError(AssertionError):
     _message = None
 
     def __init__(self, message="", **kwargs):
-        super(ValidationError, self).__init__(message)
+        super().__init__(message)
         self.errors = kwargs.get("errors", {})
         self.field_name = kwargs.get("field_name")
         self.message = message
 
     def __str__(self):
-        return six.text_type(self.message)
+        return str(self.message)
 
     def __repr__(self):
-        return "%s(%s,)" % (self.__class__.__name__, self.message)
+        return f"{self.__class__.__name__}({self.message},)"
 
     def __getattribute__(self, name):
-        message = super(ValidationError, self).__getattribute__(name)
+        message = super().__getattribute__(name)
         if name == "message":
             if self.field_name:
                 message = "%s" % message
             if self.errors:
-                message = "%s(%s)" % (message, self._format_errors())
+                message = f"{message}({self._format_errors()})"
         return message
 
     def _get_message(self):
@@ -126,12 +124,12 @@ class ValidationError(AssertionError):
         def build_dict(source):
             errors_dict = {}
             if isinstance(source, dict):
-                for field_name, error in iteritems(source):
+                for field_name, error in source.items():
                     errors_dict[field_name] = build_dict(error)
             elif isinstance(source, ValidationError) and source.errors:
                 return build_dict(source.errors)
             else:
-                return six.text_type(source)
+                return str(source)
 
             return errors_dict
 
@@ -147,15 +145,15 @@ class ValidationError(AssertionError):
             if isinstance(value, list):
                 value = " ".join([generate_key(k) for k in value])
             elif isinstance(value, dict):
-                value = " ".join([generate_key(v, k) for k, v in iteritems(value)])
+                value = " ".join([generate_key(v, k) for k, v in value.items()])
 
-            results = "%s.%s" % (prefix, value) if prefix else value
+            results = f"{prefix}.{value}" if prefix else value
             return results
 
         error_dict = defaultdict(list)
-        for k, v in iteritems(self.to_dict()):
+        for k, v in self.to_dict().items():
             error_dict[generate_key(v)].append(k)
-        return " ".join(["%s: %s" % (k, v) for k, v in iteritems(error_dict)])
+        return " ".join([f"{k}: {v}" for k, v in error_dict.items()])
 
 
 class DeprecatedError(Exception):

mongoengine/mongodb_support.py

@@ -11,7 +11,7 @@ MONGODB_36 = (3, 6)
 
 
 def get_mongodb_version():
-    """Return the version of the connected mongoDB (first 2 digits)
+    """Return the version of the default connected mongoDB (first 2 digits)
 
     :return: tuple(int, int)
     """

mongoengine/pymongo_support.py

@@ -2,6 +2,7 @@
 Helper functions, constants, and types to aid with PyMongo v2.7 - v3.x support.
 """
 import pymongo
+from pymongo.errors import OperationFailure
 
 _PYMONGO_37 = (3, 7)
 
@@ -10,13 +11,40 @@ PYMONGO_VERSION = tuple(pymongo.version_tuple[:2])
 IS_PYMONGO_GTE_37 = PYMONGO_VERSION >= _PYMONGO_37
 
 
-def count_documents(collection, filter):
+def count_documents(
+    collection, filter, skip=None, limit=None, hint=None, collation=None
+):
     """Pymongo>3.7 deprecates count in favour of count_documents"""
+    if limit == 0:
+        return 0  # Pymongo raises an OperationFailure if called with limit=0
+
+    kwargs = {}
+    if skip is not None:
+        kwargs["skip"] = skip
+    if limit is not None:
+        kwargs["limit"] = limit
+    if hint not in (-1, None):
+        kwargs["hint"] = hint
+    if collation is not None:
+        kwargs["collation"] = collation
+
+    # count_documents appeared in pymongo 3.7
     if IS_PYMONGO_GTE_37:
-        return collection.count_documents(filter)
+        try:
-    else:
+            return collection.count_documents(filter=filter, **kwargs)
-        count = collection.find(filter).count()
+        except OperationFailure:
-    return count
+            # OperationFailure - accounts for some operators that used to work
+            # with .count but are no longer working with count_documents (i.e $geoNear, $near, and $nearSphere)
+            # fallback to deprecated Cursor.count
+            # Keeping this should be reevaluated the day pymongo removes .count entirely
+            pass
+
+    cursor = collection.find(filter)
+    for option, option_value in kwargs.items():
+        cursor_method = getattr(cursor, option)
+        cursor = cursor_method(option_value)
+    with_limit_and_skip = "skip" in kwargs or "limit" in kwargs
+    return cursor.count(with_limit_and_skip=with_limit_and_skip)
 
 
 def list_collection_names(db, include_system_collections=False):

mongoengine/python_support.py

@@ -1,23 +0,0 @@
-"""
-Helper functions, constants, and types to aid with Python v2.7 - v3.x support
-"""
-import six
-
-# six.BytesIO resolves to StringIO.StringIO in Py2 and io.BytesIO in Py3.
-StringIO = six.BytesIO
-
-# Additionally for Py2, try to use the faster cStringIO, if available
-if not six.PY3:
-    try:
-        import cStringIO
-    except ImportError:
-        pass
-    else:
-        StringIO = cStringIO.StringIO
-
-
-if six.PY3:
-    from collections.abc import Hashable
-else:
-    # raises DeprecationWarnings in Python >=3.7
-    from collections import Hashable

mongoengine/queryset/base.py

@@ -1,24 +1,27 @@
-from __future__ import absolute_import
-
 import copy
 import itertools
 import re
 import warnings
 
+from collections.abc import Mapping
+
 from bson import SON, json_util
 from bson.code import Code
 import pymongo
 import pymongo.errors
 from pymongo.collection import ReturnDocument
 from pymongo.common import validate_read_preference
-import six
+from pymongo.read_concern import ReadConcern
-from six import iteritems
 
 from mongoengine import signals
 from mongoengine.base import get_document
 from mongoengine.common import _import_class
 from mongoengine.connection import get_db
-from mongoengine.context_managers import set_write_concern, switch_db
+from mongoengine.context_managers import (
+    set_read_write_concern,
+    set_write_concern,
+    switch_db,
+)
 from mongoengine.errors import (
     BulkWriteError,
     InvalidQueryError,
@@ -26,6 +29,7 @@ from mongoengine.errors import (
     NotUniqueError,
     OperationError,
 )
+from mongoengine.pymongo_support import count_documents
 from mongoengine.queryset import transform
 from mongoengine.queryset.field_list import QueryFieldList
 from mongoengine.queryset.visitor import Q, QNode
@@ -41,7 +45,7 @@ DENY = 3
 PULL = 4
 
 
-class BaseQuerySet(object):
+class BaseQuerySet:
     """A set of results returned from a query. Wraps a MongoDB cursor,
     providing :class:`~mongoengine.Document` objects as the results.
     """
@@ -60,8 +64,8 @@ class BaseQuerySet(object):
         self._ordering = None
         self._snapshot = False
         self._timeout = True
-        self._slave_okay = False
         self._read_preference = None
+        self._read_concern = None
         self._iter = False
         self._scalar = []
         self._none = False
@@ -80,13 +84,20 @@ class BaseQuerySet(object):
         self._cursor_obj = None
         self._limit = None
         self._skip = None
+
         self._hint = -1  # Using -1 as None is a valid value for hint
         self._collation = None
         self._batch_size = None
-        self.only_fields = []
         self._max_time_ms = None
         self._comment = None
 
+        # Hack - As people expect cursor[5:5] to return
+        # an empty result set. It's hard to do that right, though, because the
+        # server uses limit(0) to mean 'no limit'. So we set _empty
+        # in that case and check for it when iterating. We also unset
+        # it anytime we change _limit. Inspired by how it is done in pymongo.Cursor
+        self._empty = False
+
     def __call__(self, q_obj=None, **query):
         """Filter the selected documents by calling the
         :class:`~mongoengine.queryset.QuerySet` with a query.
@@ -159,6 +170,7 @@ class BaseQuerySet(object):
         [<User: User object>, <User: User object>]
         """
         queryset = self.clone()
+        queryset._empty = False
 
         # Handle a slice
         if isinstance(key, slice):
@@ -166,6 +178,8 @@ class BaseQuerySet(object):
             queryset._skip, queryset._limit = key.start, key.stop
             if key.start and key.stop:
                 queryset._limit = key.stop - key.start
+            if queryset._limit == 0:
+                queryset._empty = True
 
             # Allow further QuerySet modifications to be performed
             return queryset
@@ -177,7 +191,6 @@ class BaseQuerySet(object):
                     queryset._document._from_son(
                         queryset._cursor[key],
                         _auto_dereference=self._auto_dereference,
-                        only_fields=self.only_fields,
                     )
                 )
 
@@ -187,7 +200,6 @@ class BaseQuerySet(object):
             return queryset._document._from_son(
                 queryset._cursor[key],
                 _auto_dereference=self._auto_dereference,
-                only_fields=self.only_fields,
             )
 
         raise TypeError("Provide a slice or an integer index")
@@ -204,8 +216,6 @@ class BaseQuerySet(object):
         """Avoid to open all records in an if stmt in Py3."""
         return self._has_data()
 
-    __nonzero__ = __bool__  # For Py2 support
-
     # Core functions
 
     def all(self):
@@ -248,34 +258,30 @@ class BaseQuerySet(object):
         `DocumentName.MultipleObjectsReturned` exception if multiple results
         and :class:`~mongoengine.queryset.DoesNotExist` or
         `DocumentName.DoesNotExist` if no results are found.
-
-        .. versionadded:: 0.3
         """
         queryset = self.clone()
         queryset = queryset.order_by().limit(2)
         queryset = queryset.filter(*q_objs, **query)
 
         try:
-            result = six.next(queryset)
+            result = next(queryset)
         except StopIteration:
             msg = "%s matching query does not exist." % queryset._document._class_name
             raise queryset._document.DoesNotExist(msg)
+
         try:
-            six.next(queryset)
+            # Check if there is another match
+            next(queryset)
         except StopIteration:
             return result
 
-        # If we were able to retrieve the 2nd doc, rewind the cursor and
+        # If we were able to retrieve the 2nd doc, raise the MultipleObjectsReturned exception.
-        # raise the MultipleObjectsReturned exception.
+        raise queryset._document.MultipleObjectsReturned(
-        queryset.rewind()
+            "2 or more items returned, instead of 1"
-        message = u"%d items returned, instead of 1" % queryset.count()
+        )
-        raise queryset._document.MultipleObjectsReturned(message)
 
     def create(self, **kwargs):
-        """Create new object. Returns the saved object instance.
+        """Create new object. Returns the saved object instance."""
-
-        .. versionadded:: 0.4
-        """
         return self._document(**kwargs).save(force_insert=True)
 
     def first(self):
@@ -307,10 +313,6 @@ class BaseQuerySet(object):
 
         By default returns document instances, set ``load_bulk`` to False to
         return just ``ObjectIds``
-
-        .. versionadded:: 0.5
-        .. versionchanged:: 0.10.7
-            Add signal_kwargs argument
         """
         Document = _import_class("Document")
 
@@ -353,20 +355,20 @@ class BaseQuerySet(object):
             )
         except pymongo.errors.DuplicateKeyError as err:
             message = "Could not save document (%s)"
-            raise NotUniqueError(message % six.text_type(err))
+            raise NotUniqueError(message % err)
         except pymongo.errors.BulkWriteError as err:
             # inserting documents that already have an _id field will
             # give huge performance debt or raise
-            message = u"Bulk write error: (%s)"
+            message = "Bulk write error: (%s)"
-            raise BulkWriteError(message % six.text_type(err.details))
+            raise BulkWriteError(message % err.details)
         except pymongo.errors.OperationFailure as err:
             message = "Could not save document (%s)"
-            if re.match("^E1100[01] duplicate key", six.text_type(err)):
+            if re.match("^E1100[01] duplicate key", str(err)):
                 # E11000 - duplicate key error index
                 # E11001 - duplicate key on update
-                message = u"Tried to save duplicate unique keys (%s)"
+                message = "Tried to save duplicate unique keys (%s)"
-                raise NotUniqueError(message % six.text_type(err))
+                raise NotUniqueError(message % err)
-            raise OperationError(message % six.text_type(err))
+            raise OperationError(message % err)
 
         # Apply inserted_ids to documents
         for doc, doc_id in zip(docs, ids):
@@ -392,9 +394,36 @@ class BaseQuerySet(object):
             :meth:`skip` that has been applied to this cursor into account when
             getting the count
         """
-        if self._limit == 0 and with_limit_and_skip is False or self._none:
+        # mimic the fact that setting .limit(0) in pymongo sets no limit
+        # https://docs.mongodb.com/manual/reference/method/cursor.limit/#zero-value
+        if (
+            self._limit == 0
+            and with_limit_and_skip is False
+            or self._none
+            or self._empty
+        ):
             return 0
-        count = self._cursor.count(with_limit_and_skip=with_limit_and_skip)
+
+        kwargs = (
+            {"limit": self._limit, "skip": self._skip} if with_limit_and_skip else {}
+        )
+
+        if self._limit == 0:
+            # mimic the fact that historically .limit(0) sets no limit
+            kwargs.pop("limit", None)
+
+        if self._hint not in (-1, None):
+            kwargs["hint"] = self._hint
+
+        if self._collation:
+            kwargs["collation"] = self._collation
+
+        count = count_documents(
+            collection=self._cursor.collection,
+            filter=self._query,
+            **kwargs,
+        )
+
         self._cursor_obj = None
         return count
 
@@ -490,7 +519,13 @@ class BaseQuerySet(object):
                 return result.deleted_count
 
     def update(
-        self, upsert=False, multi=True, write_concern=None, full_result=False, **update
+        self,
+        upsert=False,
+        multi=True,
+        write_concern=None,
+        read_concern=None,
+        full_result=False,
+        **update,
     ):
         """Perform an atomic update on the fields matched by the query.
 
@@ -502,13 +537,12 @@ class BaseQuerySet(object):
             ``save(..., write_concern={w: 2, fsync: True}, ...)`` will
             wait until at least two servers have recorded the write and
             will force an fsync on the primary server.
+        :param read_concern: Override the read concern for the operation
         :param full_result: Return the associated ``pymongo.UpdateResult`` rather than just the number
             updated items
         :param update: Django-style update keyword arguments
 
         :returns the number of updated documents (unless ``full_result`` is True)
-
-        .. versionadded:: 0.2
         """
         if not update and not upsert:
             raise OperationError("No update parameters, would remove data")
@@ -528,7 +562,9 @@ class BaseQuerySet(object):
             else:
                 update["$set"] = {"_cls": queryset._document._class_name}
         try:
-            with set_write_concern(queryset._collection, write_concern) as collection:
+            with set_read_write_concern(
+                queryset._collection, write_concern, read_concern
+            ) as collection:
                 update_func = collection.update_one
                 if multi:
                     update_func = collection.update_many
@@ -538,14 +574,14 @@ class BaseQuerySet(object):
             elif result.raw_result:
                 return result.raw_result["n"]
         except pymongo.errors.DuplicateKeyError as err:
-            raise NotUniqueError(u"Update failed (%s)" % six.text_type(err))
+            raise NotUniqueError("Update failed (%s)" % err)
         except pymongo.errors.OperationFailure as err:
-            if six.text_type(err) == u"multi not coded yet":
+            if str(err) == "multi not coded yet":
-                message = u"update() method requires MongoDB 1.1.3+"
+                message = "update() method requires MongoDB 1.1.3+"
                 raise OperationError(message)
-            raise OperationError(u"Update failed (%s)" % six.text_type(err))
+            raise OperationError("Update failed (%s)" % err)
 
-    def upsert_one(self, write_concern=None, **update):
+    def upsert_one(self, write_concern=None, read_concern=None, **update):
         """Overwrite or add the first document matched by the query.
 
         :param write_concern: Extra keyword arguments are passed down which
@@ -554,19 +590,19 @@ class BaseQuerySet(object):
             ``save(..., write_concern={w: 2, fsync: True}, ...)`` will
             wait until at least two servers have recorded the write and
             will force an fsync on the primary server.
+        :param read_concern: Override the read concern for the operation
         :param update: Django-style update keyword arguments
 
         :returns the new or overwritten document
-
-        .. versionadded:: 0.10.2
         """
 
         atomic_update = self.update(
             multi=False,
             upsert=True,
             write_concern=write_concern,
+            read_concern=read_concern,
             full_result=True,
-            **update
+            **update,
         )
 
         if atomic_update.raw_result["updatedExisting"]:
@@ -591,14 +627,13 @@ class BaseQuerySet(object):
         :param update: Django-style update keyword arguments
             full_result
         :returns the number of updated documents (unless ``full_result`` is True)
-        .. versionadded:: 0.2
         """
         return self.update(
             upsert=upsert,
             multi=False,
             write_concern=write_concern,
             full_result=full_result,
-            **update
+            **update,
         )
 
     def modify(
@@ -623,8 +658,6 @@ class BaseQuerySet(object):
         :param new: return updated rather than original document
             (default ``False``)
         :param update: Django-style update keyword arguments
-
-        .. versionadded:: 0.9
         """
 
         if remove and new:
@@ -658,21 +691,19 @@ class BaseQuerySet(object):
                     upsert=upsert,
                     sort=sort,
                     return_document=return_doc,
-                    **self._cursor_args
+                    **self._cursor_args,
                 )
         except pymongo.errors.DuplicateKeyError as err:
-            raise NotUniqueError(u"Update failed (%s)" % err)
+            raise NotUniqueError("Update failed (%s)" % err)
         except pymongo.errors.OperationFailure as err:
-            raise OperationError(u"Update failed (%s)" % err)
+            raise OperationError("Update failed (%s)" % err)
 
         if full_response:
             if result["value"] is not None:
-                result["value"] = self._document._from_son(
+                result["value"] = self._document._from_son(result["value"])
-                    result["value"], only_fields=self.only_fields
-                )
         else:
             if result is not None:
-                result = self._document._from_son(result, only_fields=self.only_fields)
+                result = self._document._from_son(result)
 
         return result
 
@@ -682,8 +713,6 @@ class BaseQuerySet(object):
         `None` if no document exists with that id.
 
         :param object_id: the value for the id of the document to look up
-
-        .. versionchanged:: 0.6 Raises InvalidQueryError if filter has been set
         """
         queryset = self.clone()
         if not queryset._query_obj.empty:
@@ -692,22 +721,18 @@ class BaseQuerySet(object):
         return queryset.filter(pk=object_id).first()
 
     def in_bulk(self, object_ids):
-        """Retrieve a set of documents by their ids.
+        """ "Retrieve a set of documents by their ids.
 
-        :param object_ids: a list or tuple of ``ObjectId``\ s
+        :param object_ids: a list or tuple of ObjectId's
-        :rtype: dict of ObjectIds as keys and collection-specific
+        :rtype: dict of ObjectId's as keys and collection-specific
                 Document subclasses as values.
-
-        .. versionadded:: 0.3
         """
         doc_map = {}
 
         docs = self._collection.find({"_id": {"$in": object_ids}}, **self._cursor_args)
         if self._scalar:
             for doc in docs:
-                doc_map[doc["_id"]] = self._get_scalar(
+                doc_map[doc["_id"]] = self._get_scalar(self._document._from_son(doc))
-                    self._document._from_son(doc, only_fields=self.only_fields)
-                )
         elif self._as_pymongo:
             for doc in docs:
                 doc_map[doc["_id"]] = doc
@@ -715,14 +740,15 @@ class BaseQuerySet(object):
             for doc in docs:
                 doc_map[doc["_id"]] = self._document._from_son(
                     doc,
-                    only_fields=self.only_fields,
                     _auto_dereference=self._auto_dereference,
                 )
 
         return doc_map
 
     def none(self):
-        """Helper that just returns a list"""
+        """Returns a queryset that never returns any objects and no query will be executed when accessing the results
+        inspired by django none() https://docs.djangoproject.com/en/dev/ref/models/querysets/#none
+        """
         queryset = self.clone()
         queryset._none = True
         return queryset
@@ -742,8 +768,6 @@ class BaseQuerySet(object):
         evaluated against if you are using more than one database.
 
         :param alias: The database alias
-
-        .. versionadded:: 0.9
         """
 
         with switch_db(self._document, alias) as cls:
@@ -775,18 +799,18 @@ class BaseQuerySet(object):
             "_ordering",
             "_snapshot",
             "_timeout",
-            "_slave_okay",
             "_read_preference",
+            "_read_concern",
             "_iter",
             "_scalar",
             "_as_pymongo",
             "_limit",
             "_skip",
+            "_empty",
             "_hint",
             "_collation",
             "_auto_dereference",
             "_search_text",
-            "only_fields",
             "_max_time_ms",
             "_comment",
             "_batch_size",
@@ -805,8 +829,6 @@ class BaseQuerySet(object):
         """Handles dereferencing of :class:`~bson.dbref.DBRef` objects or
         :class:`~bson.object_id.ObjectId` a maximum depth in order to cut down
         the number queries to mongodb.
-
-        .. versionadded:: 0.5
         """
         # Make select related work the same for querysets
         max_depth += 1
@@ -822,6 +844,7 @@ class BaseQuerySet(object):
         """
         queryset = self.clone()
         queryset._limit = n
+        queryset._empty = False  # cancels the effect of empty
 
         # If a cursor object has already been created, apply the limit to it.
         if queryset._cursor_obj:
@@ -854,8 +877,6 @@ class BaseQuerySet(object):
 
         Hinting will not do anything if the corresponding index does not exist.
         The last hint applied to this cursor takes precedence over all others.
-
-        .. versionadded:: 0.5
         """
         queryset = self.clone()
         queryset._hint = index
@@ -917,10 +938,6 @@ class BaseQuerySet(object):
 
         .. note:: This is a command and won't take ordering or limit into
            account.
-
-        .. versionadded:: 0.4
-        .. versionchanged:: 0.5 - Fixed handling references
-        .. versionchanged:: 0.6 - Improved db_field refrence handling
         """
         queryset = self.clone()
 
@@ -984,12 +1001,8 @@ class BaseQuerySet(object):
         field filters.
 
         :param fields: fields to include
-
-        .. versionadded:: 0.3
-        .. versionchanged:: 0.5 - Added subfield support
         """
         fields = {f: QueryFieldList.ONLY for f in fields}
-        self.only_fields = fields.keys()
         return self.fields(True, **fields)
 
     def exclude(self, *fields):
@@ -1006,8 +1019,6 @@ class BaseQuerySet(object):
         field filters.
 
         :param fields: fields to exclude
-
-        .. versionadded:: 0.5
         """
         fields = {f: QueryFieldList.EXCLUDE for f in fields}
         return self.fields(**fields)
@@ -1026,18 +1037,18 @@ class BaseQuerySet(object):
 
             posts = BlogPost.objects(...).fields(comments=0)
 
-        To retrieve a subrange of array elements:
+        To retrieve a subrange or sublist of array elements,
+        support exist for both the `slice` and `elemMatch` projection operator:
 
             posts = BlogPost.objects(...).fields(slice__comments=5)
+            posts = BlogPost.objects(...).fields(elemMatch__comments="test")
 
         :param kwargs: A set of keyword arguments identifying what to
             include, exclude, or slice.
-
-        .. versionadded:: 0.5
         """
 
         # Check for an operator and transform to mongo-style if there is
-        operators = ["slice"]
+        operators = ["slice", "elemMatch"]
         cleaned_fields = []
         for key, value in kwargs.items():
             parts = key.split("__")
@@ -1075,8 +1086,6 @@ class BaseQuerySet(object):
         .exclude(). ::
 
             post = BlogPost.objects.exclude('comments').all_fields()
-
-        .. versionadded:: 0.5
         """
         queryset = self.clone()
         queryset._loaded_fields = QueryFieldList(
@@ -1140,7 +1149,7 @@ class BaseQuerySet(object):
 
     def explain(self):
         """Return an explain plan record for the
-        :class:`~mongoengine.queryset.QuerySet`\ 's cursor.
+        :class:`~mongoengine.queryset.QuerySet` cursor.
         """
         return self._cursor.explain()
 
@@ -1149,9 +1158,6 @@ class BaseQuerySet(object):
         """Enable or disable snapshot mode when querying.
 
         :param enabled: whether or not snapshot mode is enabled
-
-        ..versionchanged:: 0.5 - made chainable
-        .. deprecated:: Ignored with PyMongo 3+
         """
         msg = "snapshot is deprecated as it has no impact when using PyMongo 3+."
         warnings.warn(msg, DeprecationWarning)
@@ -1163,27 +1169,11 @@ class BaseQuerySet(object):
         """Enable or disable the default mongod timeout when querying. (no_cursor_timeout option)
 
         :param enabled: whether or not the timeout is used
-
-        ..versionchanged:: 0.5 - made chainable
         """
         queryset = self.clone()
         queryset._timeout = enabled
         return queryset
 
-    # DEPRECATED. Has no more impact on PyMongo 3+
-    def slave_okay(self, enabled):
-        """Enable or disable the slave_okay when querying.
-
-        :param enabled: whether or not the slave_okay is enabled
-
-        .. deprecated:: Ignored with PyMongo 3+
-        """
-        msg = "slave_okay is deprecated as it has no impact when using PyMongo 3+."
-        warnings.warn(msg, DeprecationWarning)
-        queryset = self.clone()
-        queryset._slave_okay = enabled
-        return queryset
-
     def read_preference(self, read_preference):
         """Change the read_preference when querying.
 
@@ -1196,6 +1186,22 @@ class BaseQuerySet(object):
         queryset._cursor_obj = None  # we need to re-create the cursor object whenever we apply read_preference
         return queryset
 
+    def read_concern(self, read_concern):
+        """Change the read_concern when querying.
+
+        :param read_concern: override ReplicaSetConnection-level
+            preference.
+        """
+        if read_concern is not None and not isinstance(read_concern, Mapping):
+            raise TypeError(f"{read_concern!r} is not a valid read concern.")
+
+        queryset = self.clone()
+        queryset._read_concern = (
+            ReadConcern(**read_concern) if read_concern is not None else None
+        )
+        queryset._cursor_obj = None  # we need to re-create the cursor object whenever we apply read_concern
+        return queryset
+
     def scalar(self, *fields):
         """Instead of returning Document instances, return either a specific
         value or a tuple of values in order.
@@ -1250,10 +1256,7 @@ class BaseQuerySet(object):
     def from_json(self, json_data):
         """Converts json data to unsaved objects"""
         son_data = json_util.loads(json_data)
-        return [
+        return [self._document._from_son(data) for data in son_data]
-            self._document._from_son(data, only_fields=self.only_fields)
-            for data in son_data
-        ]
 
     def aggregate(self, pipeline, *suppl_pipeline, **kwargs):
         """Perform a aggregate function based in your queryset params
@@ -1264,7 +1267,6 @@ class BaseQuerySet(object):
             parameter will be removed shortly
         :param kwargs: (optional) kwargs dictionary to be passed to pymongo's aggregate call
             See https://api.mongodb.com/python/current/api/pymongo/collection.html#pymongo.collection.Collection.aggregate
-        .. versionadded:: 0.9
         """
         using_deprecated_interface = isinstance(pipeline, dict) or bool(suppl_pipeline)
         user_pipeline = [pipeline] if isinstance(pipeline, dict) else list(pipeline)
@@ -1295,10 +1297,11 @@ class BaseQuerySet(object):
         final_pipeline = initial_pipeline + user_pipeline
 
         collection = self._collection
-        if self._read_preference is not None:
+        if self._read_preference is not None or self._read_concern is not None:
             collection = self._collection.with_options(
-                read_preference=self._read_preference
+                read_preference=self._read_preference, read_concern=self._read_concern
             )
+
         return collection.aggregate(final_pipeline, cursor={}, **kwargs)
 
     # JS functionality
@@ -1335,12 +1338,6 @@ class BaseQuerySet(object):
             Map/Reduce changed in server version **>= 1.7.4**. The PyMongo
             :meth:`~pymongo.collection.Collection.map_reduce` helper requires
             PyMongo version **>= 1.11**.
-
-        .. versionchanged:: 0.5
-           - removed ``keep_temp`` keyword argument, which was only relevant
-             for MongoDB server versions older than 1.7.4
-
-        .. versionadded:: 0.3
         """
         queryset = self.clone()
 
@@ -1352,13 +1349,13 @@ class BaseQuerySet(object):
         map_f_scope = {}
         if isinstance(map_f, Code):
             map_f_scope = map_f.scope
-            map_f = six.text_type(map_f)
+            map_f = str(map_f)
         map_f = Code(queryset._sub_js_fields(map_f), map_f_scope)
 
         reduce_f_scope = {}
         if isinstance(reduce_f, Code):
             reduce_f_scope = reduce_f.scope
-            reduce_f = six.text_type(reduce_f)
+            reduce_f = str(reduce_f)
         reduce_f_code = queryset._sub_js_fields(reduce_f)
         reduce_f = Code(reduce_f_code, reduce_f_scope)
 
@@ -1368,7 +1365,7 @@ class BaseQuerySet(object):
             finalize_f_scope = {}
             if isinstance(finalize_f, Code):
                 finalize_f_scope = finalize_f.scope
-                finalize_f = six.text_type(finalize_f)
+                finalize_f = str(finalize_f)
             finalize_f_code = queryset._sub_js_fields(finalize_f)
             finalize_f = Code(finalize_f_code, finalize_f_scope)
             mr_args["finalize"] = finalize_f
@@ -1384,7 +1381,7 @@ class BaseQuerySet(object):
         else:
             map_reduce_function = "map_reduce"
 
-            if isinstance(output, six.string_types):
+            if isinstance(output, str):
                 mr_args["out"] = output
 
             elif isinstance(output, dict):
@@ -1477,8 +1474,6 @@ class BaseQuerySet(object):
         .. note:: When using this mode of query, the database will call your
                   function, or evaluate your predicate clause, for each object
                   in the collection.
-
-        .. versionadded:: 0.5
         """
         queryset = self.clone()
         where_clause = queryset._sub_js_fields(where_clause)
@@ -1555,9 +1550,6 @@ class BaseQuerySet(object):
         :param field: the field to use
         :param normalize: normalize the results so they add to 1.0
         :param map_reduce: Use map_reduce over exec_js
-
-        .. versionchanged:: 0.5 defaults to map_reduce and can handle embedded
-                            document lookups
         """
         if map_reduce:
             return self._item_frequencies_map_reduce(field, normalize=normalize)
@@ -1566,12 +1558,11 @@ class BaseQuerySet(object):
     # Iterator helpers
 
     def __next__(self):
-        """Wrap the result in a :class:`~mongoengine.Document` object.
+        """Wrap the result in a :class:`~mongoengine.Document` object."""
-        """
+        if self._none or self._empty:
-        if self._limit == 0 or self._none:
             raise StopIteration
 
-        raw_doc = six.next(self._cursor)
+        raw_doc = next(self._cursor)
 
         if self._as_pymongo:
             return raw_doc
@@ -1579,7 +1570,6 @@ class BaseQuerySet(object):
         doc = self._document._from_son(
             raw_doc,
             _auto_dereference=self._auto_dereference,
-            only_fields=self.only_fields,
         )
 
         if self._scalar:
@@ -1587,13 +1577,8 @@ class BaseQuerySet(object):
 
         return doc
 
-    next = __next__  # For Python2 support
-
     def rewind(self):
-        """Rewind the cursor to its unevaluated state.
+        """Rewind the cursor to its unevaluated state."""
-
-        .. versionadded:: 0.3
-        """
         self._iter = False
         self._cursor.rewind()
 
@@ -1642,9 +1627,9 @@ class BaseQuerySet(object):
         # XXX In PyMongo 3+, we define the read preference on a collection
         # level, not a cursor level. Thus, we need to get a cloned collection
         # object using `with_options` first.
-        if self._read_preference is not None:
+        if self._read_preference is not None or self._read_concern is not None:
             self._cursor_obj = self._collection.with_options(
-                read_preference=self._read_preference
+                read_preference=self._read_preference, read_concern=self._read_concern
             ).find(self._query, **self._cursor_args)
         else:
             self._cursor_obj = self._collection.find(self._query, **self._cursor_args)
@@ -1816,13 +1801,13 @@ class BaseQuerySet(object):
             }
         """
         total, data, types = self.exec_js(freq_func, field)
-        values = {types.get(k): int(v) for k, v in iteritems(data)}
+        values = {types.get(k): int(v) for k, v in data.items()}
 
         if normalize:
             values = {k: float(v) / total for k, v in values.items()}
 
         frequencies = {}
-        for k, v in iteritems(values):
+        for k, v in values.items():
             if isinstance(k, float):
                 if int(k) == k:
                     k = int(k)
@@ -1842,7 +1827,7 @@ class BaseQuerySet(object):
             field_parts = field.split(".")
             try:
                 field = ".".join(
-                    f if isinstance(f, six.string_types) else f.db_field
+                    f if isinstance(f, str) else f.db_field
                     for f in self._document._lookup_field(field_parts)
                 )
                 db_field_paths.append(field)
@@ -1854,7 +1839,7 @@ class BaseQuerySet(object):
                 for subdoc in subclasses:
                     try:
                         subfield = ".".join(
-                            f if isinstance(f, six.string_types) else f.db_field
+                            f if isinstance(f, str) else f.db_field
                             for f in subdoc._lookup_field(field_parts)
                         )
                         db_field_paths.append(subfield)
@@ -1928,7 +1913,7 @@ class BaseQuerySet(object):
             field_name = match.group(1).split(".")
             fields = self._document._lookup_field(field_name)
             # Substitute the correct name for the field into the javascript
-            return u'["%s"]' % fields[-1].db_field
+            return '["%s"]' % fields[-1].db_field
 
         def field_path_sub(match):
             # Extract just the field name, and look up the field objects
@@ -1958,23 +1943,3 @@ class BaseQuerySet(object):
         setattr(queryset, "_" + method_name, val)
 
         return queryset
-
-    # Deprecated
-    def ensure_index(self, **kwargs):
-        """Deprecated use :func:`Document.ensure_index`"""
-        msg = (
-            "Doc.objects()._ensure_index() is deprecated. "
-            "Use Doc.ensure_index() instead."
-        )
-        warnings.warn(msg, DeprecationWarning)
-        self._document.__class__.ensure_index(**kwargs)
-        return self
-
-    def _ensure_indexes(self):
-        """Deprecated use :func:`~Document.ensure_indexes`"""
-        msg = (
-            "Doc.objects()._ensure_indexes() is deprecated. "
-            "Use Doc.ensure_indexes() instead."
-        )
-        warnings.warn(msg, DeprecationWarning)
-        self._document.__class__.ensure_indexes()

mongoengine/queryset/field_list.py

@@ -1,7 +1,7 @@
 __all__ = ("QueryFieldList",)
 
 
-class QueryFieldList(object):
+class QueryFieldList:
     """Object that handles combinations of .only() and .exclude() calls"""
 
     ONLY = 1
@@ -69,8 +69,6 @@ class QueryFieldList(object):
     def __bool__(self):
         return bool(self.fields)
 
-    __nonzero__ = __bool__  # For Py2 support
-
     def as_dict(self):
         field_list = {field: self.value for field in self.fields}
         if self.slice:
@@ -80,7 +78,7 @@ class QueryFieldList(object):
         return field_list
 
     def reset(self):
-        self.fields = set([])
+        self.fields = set()
         self.slice = {}
         self.value = self.ONLY
 

mongoengine/queryset/manager.py

@@ -4,7 +4,7 @@ from mongoengine.queryset.queryset import QuerySet
 __all__ = ("queryset_manager", "QuerySetManager")
 
 
-class QuerySetManager(object):
+class QuerySetManager:
     """
     The default QuerySet Manager.
 

mongoengine/queryset/queryset.py

@@ -1,5 +1,3 @@
-import six
-
 from mongoengine.errors import OperationError
 from mongoengine.queryset.base import (
     BaseQuerySet,
@@ -127,8 +125,8 @@ class QuerySet(BaseQuerySet):
         # Pull in ITER_CHUNK_SIZE docs from the database and store them in
         # the result cache.
         try:
-            for _ in six.moves.range(ITER_CHUNK_SIZE):
+            for _ in range(ITER_CHUNK_SIZE):
-                self._result_cache.append(six.next(self))
+                self._result_cache.append(next(self))
         except StopIteration:
             # Getting this exception means there are no more docs in the
             # db cursor. Set _has_more to False so that we can use that
@@ -143,18 +141,16 @@ class QuerySet(BaseQuerySet):
             getting the count
         """
         if with_limit_and_skip is False:
-            return super(QuerySet, self).count(with_limit_and_skip)
+            return super().count(with_limit_and_skip)
 
         if self._len is None:
-            self._len = super(QuerySet, self).count(with_limit_and_skip)
+            # cache the length
+            self._len = super().count(with_limit_and_skip)
 
         return self._len
 
     def no_cache(self):
-        """Convert to a non-caching queryset
+        """Convert to a non-caching queryset"""
-
-        .. versionadded:: 0.8.3 Convert to non caching queryset
-        """
         if self._result_cache is not None:
             raise OperationError("QuerySet already cached")
 
@@ -165,24 +161,18 @@ class QuerySetNoCache(BaseQuerySet):
     """A non caching QuerySet"""
 
     def cache(self):
-        """Convert to a caching queryset
+        """Convert to a caching queryset"""
-
-        .. versionadded:: 0.8.3 Convert to caching queryset
-        """
         return self._clone_into(QuerySet(self._document, self._collection))
 
     def __repr__(self):
-        """Provides the string representation of the QuerySet
+        """Provides the string representation of the QuerySet"""
-
-        .. versionchanged:: 0.6.13 Now doesnt modify the cursor
-        """
         if self._iter:
             return ".. queryset mid-iteration .."
 
         data = []
-        for _ in six.moves.range(REPR_OUTPUT_SIZE + 1):
+        for _ in range(REPR_OUTPUT_SIZE + 1):
             try:
-                data.append(six.next(self))
+                data.append(next(self))
             except StopIteration:
                 break
 

mongoengine/queryset/transform.py

@@ -3,14 +3,12 @@ from collections import defaultdict
 from bson import ObjectId, SON
 from bson.dbref import DBRef
 import pymongo
-import six
-from six import iteritems
 
 from mongoengine.base import UPDATE_OPERATORS
 from mongoengine.common import _import_class
 from mongoengine.errors import InvalidQueryError
 
-__all__ = ("query", "update")
+__all__ = ("query", "update", "STRING_OPERATORS")
 
 COMPARISON_OPERATORS = (
     "ne",
@@ -101,7 +99,7 @@ def query(_doc_cls=None, **kwargs):
             cleaned_fields = []
             for field in fields:
                 append_field = True
-                if isinstance(field, six.string_types):
+                if isinstance(field, str):
                     parts.append(field)
                     append_field = False
                 # is last and CachedReferenceField
@@ -169,9 +167,9 @@ def query(_doc_cls=None, **kwargs):
 
         key = ".".join(parts)
 
-        if op is None or key not in mongo_query:
+        if key not in mongo_query:
             mongo_query[key] = value
-        elif key in mongo_query:
+        else:
             if isinstance(mongo_query[key], dict) and isinstance(value, dict):
                 mongo_query[key].update(value)
                 # $max/minDistance needs to come last - convert to SON
@@ -180,7 +178,7 @@ def query(_doc_cls=None, **kwargs):
                     "$near" in value_dict or "$nearSphere" in value_dict
                 ):
                     value_son = SON()
-                    for k, v in iteritems(value_dict):
+                    for k, v in value_dict.items():
                         if k == "$maxDistance" or k == "$minDistance":
                             continue
                         value_son[k] = v
@@ -281,7 +279,7 @@ def update(_doc_cls=None, **update):
             appended_sub_field = False
             for field in fields:
                 append_field = True
-                if isinstance(field, six.string_types):
+                if isinstance(field, str):
                     # Convert the S operator to $
                     if field == "S":
                         field = "$"
@@ -435,7 +433,9 @@ def _geo_operator(field, op, value):
             value = {"$near": _infer_geometry(value)}
         else:
             raise NotImplementedError(
-                'Geo method "%s" has not been implemented for a %s ' % (op, field._name)
+                'Geo method "{}" has not been implemented for a {} '.format(
+                    op, field._name
+                )
             )
     return value
 

mongoengine/queryset/visitor.py

@@ -7,18 +7,20 @@ from mongoengine.queryset import transform
 __all__ = ("Q", "QNode")
 
 
-class QNodeVisitor(object):
+def warn_empty_is_deprecated():
-    """Base visitor class for visiting Q-object nodes in a query tree.
+    msg = "'empty' property is deprecated in favour of using 'not bool(filter)'"
-    """
+    warnings.warn(msg, DeprecationWarning, stacklevel=2)
+
+
+class QNodeVisitor:
+    """Base visitor class for visiting Q-object nodes in a query tree."""
 
     def visit_combination(self, combination):
-        """Called by QCombination objects.
+        """Called by QCombination objects."""
-        """
         return combination
 
     def visit_query(self, query):
-        """Called by (New)Q objects.
+        """Called by (New)Q objects."""
-        """
         return query
 
 
@@ -44,8 +46,7 @@ class SimplificationVisitor(QNodeVisitor):
         return combination
 
     def _query_conjunction(self, queries):
-        """Merges query dicts - effectively &ing them together.
+        """Merges query dicts - effectively &ing them together."""
-        """
         query_ops = set()
         combined_query = {}
         for query in queries:
@@ -79,7 +80,7 @@ class QueryCompilerVisitor(QNodeVisitor):
         return transform.query(self.document, **query.query)
 
 
-class QNode(object):
+class QNode:
     """Base class for nodes in query trees."""
 
     AND = 0
@@ -98,19 +99,18 @@ class QNode(object):
         object.
         """
         # If the other Q() is empty, ignore it and just use `self`.
-        if getattr(other, "empty", True):
+        if not bool(other):
             return self
 
         # Or if this Q is empty, ignore it and just use `other`.
-        if self.empty:
+        if not bool(self):
             return other
 
         return QCombination(operation, [self, other])
 
     @property
     def empty(self):
-        msg = "'empty' property is deprecated in favour of using 'not bool(filter)'"
+        warn_empty_is_deprecated()
-        warnings.warn(msg, DeprecationWarning)
         return False
 
     def __or__(self, other):
@@ -143,8 +143,6 @@ class QCombination(QNode):
     def __bool__(self):
         return bool(self.children)
 
-    __nonzero__ = __bool__  # For Py2 support
-
     def accept(self, visitor):
         for i in range(len(self.children)):
             if isinstance(self.children[i], QNode):
@@ -154,8 +152,7 @@ class QCombination(QNode):
 
     @property
     def empty(self):
-        msg = "'empty' property is deprecated in favour of using 'not bool(filter)'"
+        warn_empty_is_deprecated()
-        warnings.warn(msg, DeprecationWarning)
         return not bool(self.children)
 
     def __eq__(self, other):
@@ -180,8 +177,6 @@ class Q(QNode):
     def __bool__(self):
         return bool(self.query)
 
-    __nonzero__ = __bool__  # For Py2 support
-
     def __eq__(self, other):
         return self.__class__ == other.__class__ and self.query == other.query
 
@@ -190,4 +185,5 @@ class Q(QNode):
 
     @property
     def empty(self):
+        warn_empty_is_deprecated()
         return not bool(self.query)

mongoengine/signals.py

@@ -15,11 +15,11 @@ try:
     signals_available = True
 except ImportError:
 
-    class Namespace(object):
+    class Namespace:
         def signal(self, name, doc=None):
             return _FakeSignal(name, doc)
 
-    class _FakeSignal(object):
+    class _FakeSignal:
         """If blinker is unavailable, create a fake class with the same
         interface that allows sending of signals but will fail with an
         error on anything else.  Instead of doing anything on send, it

python-mongoengine.spec

@@ -51,4 +51,4 @@ rm -rf $RPM_BUILD_ROOT
 # %{python_sitearch}/*
 
 %changelog
-* See: http://docs.mongoengine.org/en/latest/changelog.html
+* See: http://docs.mongoengine.org/en/latest/changelog.html

requirements-dev.txt

@@ -0,0 +1,8 @@
+black
+flake8
+flake8-import-order
+pre-commit
+pytest
+ipdb
+ipython
+tox

requirements-lint.txt

@@ -1,3 +0,0 @@
-black
-flake8
-flake8-import-order

requirements.txt

@@ -1,4 +0,0 @@
-pymongo>=3.4
-six==1.10.0
-Sphinx==1.5.5
-sphinx-rtd-theme==0.2.4

setup.cfg

@@ -1,5 +1,5 @@
 [flake8]
-ignore=E501,F401,F403,F405,I201,I202,W504, W605, W503
+ignore=E501,F403,F405,I201,I202,W504,W605,W503,B007
 exclude=build,dist,docs,venv,venv3,.tox,.eggs,tests
 max-complexity=47
 application-import-names=mongoengine,tests

setup.py

@@ -7,7 +7,7 @@ from setuptools.command.test import test as TestCommand
 
 # Hack to silence atexit traceback in newer python versions
 try:
-    import multiprocessing
+    import multiprocessing  # noqa: F401
 except ImportError:
     pass
 
@@ -92,16 +92,16 @@ version_line = list(filter(lambda l: l.startswith("VERSION"), open(init)))[0]
 VERSION = get_version(eval(version_line.split("=")[-1]))
 
 CLASSIFIERS = [
-    "Development Status :: 4 - Beta",
+    "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 2",
-    "Programming Language :: Python :: 2.7",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.5",
     "Programming Language :: Python :: 3.6",
+    "Programming Language :: Python :: 3.7",
+    "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     "Topic :: Database",
@@ -115,18 +115,15 @@ extra_opts = {
         "pytest-cov",
         "coverage<5.0",  # recent coverage switched to sqlite format for the .coverage file which isn't handled properly by coveralls
         "blinker",
-        "Pillow>=2.0.0, <7.0.0",  # 7.0.0 dropped Python2 support
+        "Pillow>=7.0.0",
     ],
 }
-if sys.version_info[0] == 3:
+
-    extra_opts["use_2to3"] = True
+if "test" in sys.argv:
-    if "test" in sys.argv:
+    extra_opts["packages"] = find_packages()
-        extra_opts["packages"] = find_packages()
+    extra_opts["package_data"] = {
-        extra_opts["package_data"] = {
+        "tests": ["fields/mongoengine.png", "fields/mongodb_leaf.png"]
-            "tests": ["fields/mongoengine.png", "fields/mongodb_leaf.png"]
+    }
-        }
-else:
-    extra_opts["tests_require"] += ["python-dateutil"]
 
 setup(
     name="mongoengine",
@@ -143,7 +140,8 @@ setup(
     long_description=LONG_DESCRIPTION,
     platforms=["any"],
     classifiers=CLASSIFIERS,
-    install_requires=["pymongo>=3.4", "six>=1.10.0"],
+    python_requires=">=3.5",
+    install_requires=["pymongo>=3.4, <4.0"],
     cmdclass={"test": PyTest},
     **extra_opts
 )

tests/document/test_class_methods.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import unittest
 
 from mongoengine import *
@@ -27,16 +26,14 @@ class TestClassMethods(unittest.TestCase):
             self.db.drop_collection(collection)
 
     def test_definition(self):
-        """Ensure that document may be defined using fields.
+        """Ensure that document may be defined using fields."""
-        """
         assert ["_cls", "age", "id", "name"] == sorted(self.Person._fields.keys())
         assert ["IntField", "ObjectIdField", "StringField", "StringField"] == sorted(
-            [x.__class__.__name__ for x in self.Person._fields.values()]
+            x.__class__.__name__ for x in self.Person._fields.values()
         )
 
     def test_get_db(self):
-        """Ensure that get_db returns the expected db.
+        """Ensure that get_db returns the expected db."""
-        """
         db = self.Person._get_db()
         assert self.db == db
 
@@ -48,15 +45,13 @@ class TestClassMethods(unittest.TestCase):
         assert collection_name == self.Person._get_collection_name()
 
     def test_get_collection(self):
-        """Ensure that get_collection returns the expected collection.
+        """Ensure that get_collection returns the expected collection."""
-        """
         collection_name = "person"
         collection = self.Person._get_collection()
         assert self.db[collection_name] == collection
 
     def test_drop_collection(self):
-        """Ensure that the collection may be dropped from the database.
+        """Ensure that the collection may be dropped from the database."""
-        """
         collection_name = "person"
         self.Person(name="Test").save()
         assert collection_name in list_collection_names(self.db)
@@ -78,7 +73,7 @@ class TestClassMethods(unittest.TestCase):
         assert self.Person._meta["delete_rules"] == {(Job, "employee"): NULLIFY}
 
     def test_compare_indexes(self):
-        """ Ensure that the indexes are properly created and that
+        """Ensure that the indexes are properly created and that
         compare_indexes identifies the missing/extra indexes
         """
 
@@ -111,7 +106,7 @@ class TestClassMethods(unittest.TestCase):
         }
 
     def test_compare_indexes_inheritance(self):
-        """ Ensure that the indexes are properly created and that
+        """Ensure that the indexes are properly created and that
         compare_indexes identifies the missing/extra indexes for subclassed
         documents (_cls included)
         """
@@ -151,7 +146,7 @@ class TestClassMethods(unittest.TestCase):
         }
 
     def test_compare_indexes_multiple_subclasses(self):
-        """ Ensure that compare_indexes behaves correctly if called from a
+        """Ensure that compare_indexes behaves correctly if called from a
         class, which base class has multiple subclasses
         """
 
@@ -204,7 +199,7 @@ class TestClassMethods(unittest.TestCase):
         assert actual == expected
 
     def test_list_indexes_inheritance(self):
-        """ ensure that all of the indexes are listed regardless of the super-
+        """ensure that all of the indexes are listed regardless of the super-
         or sub-class that we call it from
         """
 
@@ -236,7 +231,7 @@ class TestClassMethods(unittest.TestCase):
         assert BlogPost.list_indexes() == [
             [("_cls", 1), ("author", 1), ("tags", 1)],
             [("_cls", 1), ("author", 1), ("tags", 1), ("extra_text", 1)],
-            [(u"_id", 1)],
+            [("_id", 1)],
             [("_cls", 1)],
         ]
 
@@ -261,8 +256,7 @@ class TestClassMethods(unittest.TestCase):
         assert Vaccine._meta["delete_rules"][(Cat, "vaccine_made")] == PULL
 
     def test_collection_naming(self):
-        """Ensure that a collection with a specified name may be used.
+        """Ensure that a collection with a specified name may be used."""
-        """
 
         class DefaultNamingTest(Document):
             pass
@@ -294,7 +288,7 @@ class TestClassMethods(unittest.TestCase):
         assert "wibble" == InheritedAbstractNamingTest._get_collection_name()
 
         # Mixin tests
-        class BaseMixin(object):
+        class BaseMixin:
             meta = {"collection": lambda c: c.__name__.lower()}
 
         class OldMixinNamingConvention(Document, BaseMixin):
@@ -305,7 +299,7 @@ class TestClassMethods(unittest.TestCase):
             == OldMixinNamingConvention._get_collection_name()
         )
 
-        class BaseMixin(object):
+        class BaseMixin:
             meta = {"collection": lambda c: c.__name__.lower()}
 
         class BaseDocument(Document, BaseMixin):
@@ -317,8 +311,7 @@ class TestClassMethods(unittest.TestCase):
         assert "basedocument" == MyDocument._get_collection_name()
 
     def test_custom_collection_name_operations(self):
-        """Ensure that a collection with a specified name is used as expected.
+        """Ensure that a collection with a specified name is used as expected."""
-        """
         collection_name = "personCollTest"
 
         class Person(Document):
@@ -338,8 +331,7 @@ class TestClassMethods(unittest.TestCase):
         assert collection_name not in list_collection_names(self.db)
 
     def test_collection_name_and_primary(self):
-        """Ensure that a collection with a specified name may be used.
+        """Ensure that a collection with a specified name may be used."""
-        """
 
         class Person(Document):
             name = StringField(primary_key=True)

tests/document/test_delta.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import unittest
 
 from bson import SON
@@ -9,7 +8,7 @@ from tests.utils import MongoDBTestCase
 
 class TestDelta(MongoDBTestCase):
     def setUp(self):
-        super(TestDelta, self).setUp()
+        super().setUp()
 
         class Person(Document):
             name = StringField()
@@ -29,7 +28,8 @@ class TestDelta(MongoDBTestCase):
         self.delta(Document)
         self.delta(DynamicDocument)
 
-    def delta(self, DocClass):
+    @staticmethod
+    def delta(DocClass):
         class Doc(DocClass):
             string_field = StringField()
             int_field = IntField()
@@ -428,13 +428,20 @@ class TestDelta(MongoDBTestCase):
         assert doc.dict_field == {"hello": "world"}
         assert doc.list_field == ["1", 2, {"hello": "world"}]
 
-    def test_delta_recursive_db_field(self):
+    def test_delta_recursive_db_field_on_doc_and_embeddeddoc(self):
         self.delta_recursive_db_field(Document, EmbeddedDocument)
+
+    def test_delta_recursive_db_field_on_doc_and_dynamicembeddeddoc(self):
         self.delta_recursive_db_field(Document, DynamicEmbeddedDocument)
+
+    def test_delta_recursive_db_field_on_dynamicdoc_and_embeddeddoc(self):
         self.delta_recursive_db_field(DynamicDocument, EmbeddedDocument)
+
+    def test_delta_recursive_db_field_on_dynamicdoc_and_dynamicembeddeddoc(self):
         self.delta_recursive_db_field(DynamicDocument, DynamicEmbeddedDocument)
 
-    def delta_recursive_db_field(self, DocClass, EmbeddedClass):
+    @staticmethod
+    def delta_recursive_db_field(DocClass, EmbeddedClass):
         class Embedded(EmbeddedClass):
             string_field = StringField(db_field="db_string_field")
             int_field = IntField(db_field="db_int_field")
@@ -487,6 +494,7 @@ class TestDelta(MongoDBTestCase):
         doc = doc.reload(10)
         assert doc.embedded_field.dict_field == {}
 
+        assert doc._get_changed_fields() == []
         doc.embedded_field.list_field = []
         assert doc._get_changed_fields() == ["db_embedded_field.db_list_field"]
         assert doc.embedded_field._delta() == ({}, {"db_list_field": 1})
@@ -537,6 +545,7 @@ class TestDelta(MongoDBTestCase):
             {},
         )
         doc.save()
+        assert doc._get_changed_fields() == []
         doc = doc.reload(10)
 
         assert doc.embedded_field.list_field[0] == "1"
@@ -634,6 +643,10 @@ class TestDelta(MongoDBTestCase):
         doc.save()
         doc = doc.reload(10)
 
+        assert doc._delta() == (
+            {},
+            {},
+        )
         del doc.embedded_field.list_field[2].list_field
         assert doc._delta() == (
             {},
@@ -732,12 +745,12 @@ class TestDelta(MongoDBTestCase):
         assert organization._get_changed_fields() == []
 
         updates, removals = organization._delta()
-        assert {} == removals
+        assert removals == {}
-        assert {} == updates
+        assert updates == {}
 
         organization.employees.append(person)
         updates, removals = organization._delta()
-        assert {} == removals
+        assert removals == {}
         assert "employees" in updates
 
     def test_delta_with_dbref_false(self):
@@ -749,12 +762,12 @@ class TestDelta(MongoDBTestCase):
         assert organization._get_changed_fields() == []
 
         updates, removals = organization._delta()
-        assert {} == removals
+        assert removals == {}
-        assert {} == updates
+        assert updates == {}
 
         organization.employees.append(person)
         updates, removals = organization._delta()
-        assert {} == removals
+        assert removals == {}
         assert "employees" in updates
 
     def test_nested_nested_fields_mark_as_changed(self):
@@ -767,19 +780,46 @@ class TestDelta(MongoDBTestCase):
 
         MyDoc.drop_collection()
 
-        mydoc = MyDoc(
+        MyDoc(name="testcase1", subs={"a": {"b": EmbeddedDoc(name="foo")}}).save()
-            name="testcase1", subs={"a": {"b": EmbeddedDoc(name="foo")}}
-        ).save()
 
         mydoc = MyDoc.objects.first()
         subdoc = mydoc.subs["a"]["b"]
         subdoc.name = "bar"
 
-        assert ["name"] == subdoc._get_changed_fields()
+        assert subdoc._get_changed_fields() == ["name"]
-        assert ["subs.a.b.name"] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == ["subs.a.b.name"]
 
         mydoc._clear_changed_fields()
-        assert [] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == []
+
+    def test_nested_nested_fields_db_field_set__gets_mark_as_changed_and_cleaned(self):
+        class EmbeddedDoc(EmbeddedDocument):
+            name = StringField(db_field="db_name")
+
+        class MyDoc(Document):
+            embed = EmbeddedDocumentField(EmbeddedDoc, db_field="db_embed")
+            name = StringField(db_field="db_name")
+
+        MyDoc.drop_collection()
+
+        MyDoc(name="testcase1", embed=EmbeddedDoc(name="foo")).save()
+
+        mydoc = MyDoc.objects.first()
+        mydoc.embed.name = "foo1"
+
+        assert mydoc.embed._get_changed_fields() == ["db_name"]
+        assert mydoc._get_changed_fields() == ["db_embed.db_name"]
+
+        mydoc = MyDoc.objects.first()
+        embed = EmbeddedDoc(name="foo2")
+        embed.name = "bar"
+        mydoc.embed = embed
+
+        assert embed._get_changed_fields() == ["db_name"]
+        assert mydoc._get_changed_fields() == ["db_embed"]
+
+        mydoc._clear_changed_fields()
+        assert mydoc._get_changed_fields() == []
 
     def test_lower_level_mark_as_changed(self):
         class EmbeddedDoc(EmbeddedDocument):
@@ -794,17 +834,17 @@ class TestDelta(MongoDBTestCase):
 
         mydoc = MyDoc.objects.first()
         mydoc.subs["a"] = EmbeddedDoc()
-        assert ["subs.a"] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == ["subs.a"]
 
         subdoc = mydoc.subs["a"]
         subdoc.name = "bar"
 
-        assert ["name"] == subdoc._get_changed_fields()
+        assert subdoc._get_changed_fields() == ["name"]
-        assert ["subs.a"] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == ["subs.a"]
         mydoc.save()
 
         mydoc._clear_changed_fields()
-        assert [] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == []
 
     def test_upper_level_mark_as_changed(self):
         class EmbeddedDoc(EmbeddedDocument):
@@ -821,15 +861,15 @@ class TestDelta(MongoDBTestCase):
         subdoc = mydoc.subs["a"]
         subdoc.name = "bar"
 
-        assert ["name"] == subdoc._get_changed_fields()
+        assert subdoc._get_changed_fields() == ["name"]
-        assert ["subs.a.name"] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == ["subs.a.name"]
 
         mydoc.subs["a"] = EmbeddedDoc()
-        assert ["subs.a"] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == ["subs.a"]
         mydoc.save()
 
         mydoc._clear_changed_fields()
-        assert [] == mydoc._get_changed_fields()
+        assert mydoc._get_changed_fields() == []
 
     def test_referenced_object_changed_attributes(self):
         """Ensures that when you save a new reference to a field, the referenced object isn't altered"""

tests/document/test_dynamic.py

@@ -10,7 +10,7 @@ __all__ = ("TestDynamicDocument",)
 
 class TestDynamicDocument(MongoDBTestCase):
     def setUp(self):
-        super(TestDynamicDocument, self).setUp()
+        super().setUp()
 
         class Person(DynamicDocument):
             name = StringField()
@@ -37,6 +37,19 @@ class TestDynamicDocument(MongoDBTestCase):
         # Confirm no changes to self.Person
         assert not hasattr(self.Person, "age")
 
+    def test_dynamic_document_parse_values_in_constructor_like_document_do(self):
+        class ProductDynamicDocument(DynamicDocument):
+            title = StringField()
+            price = FloatField()
+
+        class ProductDocument(Document):
+            title = StringField()
+            price = FloatField()
+
+        product = ProductDocument(title="Blabla", price="12.5")
+        dyn_product = ProductDynamicDocument(title="Blabla", price="12.5")
+        assert product.price == dyn_product.price == 12.5
+
     def test_change_scope_of_variable(self):
         """Test changing the scope of a dynamic field has no adverse effects"""
         p = self.Person()
@@ -105,17 +118,17 @@ class TestDynamicDocument(MongoDBTestCase):
         p.save()
 
         raw_p = Person.objects.as_pymongo().get(id=p.id)
-        assert raw_p == {"_cls": u"Person", "_id": p.id, "name": u"Dean"}
+        assert raw_p == {"_cls": "Person", "_id": p.id, "name": "Dean"}
 
         p.name = "OldDean"
         p.newattr = "garbage"
         p.save()
         raw_p = Person.objects.as_pymongo().get(id=p.id)
         assert raw_p == {
-            "_cls": u"Person",
+            "_cls": "Person",
             "_id": p.id,
             "name": "OldDean",
-            "newattr": u"garbage",
+            "newattr": "garbage",
         }
 
     def test_fields_containing_underscore(self):
@@ -131,14 +144,14 @@ class TestDynamicDocument(MongoDBTestCase):
         p.save()
 
         raw_p = WeirdPerson.objects.as_pymongo().get(id=p.id)
-        assert raw_p == {"_id": p.id, "_name": u"Dean", "name": u"Dean"}
+        assert raw_p == {"_id": p.id, "_name": "Dean", "name": "Dean"}
 
         p.name = "OldDean"
         p._name = "NewDean"
         p._newattr1 = "garbage"  # Unknown fields won't be added
         p.save()
         raw_p = WeirdPerson.objects.as_pymongo().get(id=p.id)
-        assert raw_p == {"_id": p.id, "_name": u"NewDean", "name": u"OldDean"}
+        assert raw_p == {"_id": p.id, "_name": "NewDean", "name": "OldDean"}
 
     def test_dynamic_document_queries(self):
         """Ensure we can query dynamic fields"""

tests/document/test_indexes.py

@@ -1,11 +1,9 @@
-# -*- coding: utf-8 -*-
 import unittest
 from datetime import datetime
 
 from pymongo.collation import Collation
 from pymongo.errors import OperationFailure
 import pytest
-from six import iteritems
 
 from mongoengine import *
 from mongoengine.connection import get_db
@@ -59,7 +57,7 @@ class TestIndexes(unittest.TestCase):
         info = BlogPost.objects._collection.index_information()
         # _id, '-date', 'tags', ('cat', 'date')
         assert len(info) == 4
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         for expected in expected_specs:
             assert expected["fields"] in info
 
@@ -87,7 +85,7 @@ class TestIndexes(unittest.TestCase):
         # the indices on -date and tags will both contain
         # _cls as first element in the key
         assert len(info) == 4
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         for expected in expected_specs:
             assert expected["fields"] in info
 
@@ -102,7 +100,7 @@ class TestIndexes(unittest.TestCase):
 
         ExtendedBlogPost.ensure_indexes()
         info = ExtendedBlogPost.objects._collection.index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         for expected in expected_specs:
             assert expected["fields"] in info
 
@@ -173,8 +171,7 @@ class TestIndexes(unittest.TestCase):
         assert MyDoc._meta["index_specs"] == [{"fields": [("keywords", 1)]}]
 
     def test_embedded_document_index_meta(self):
-        """Ensure that embedded document indexes are created explicitly
+        """Ensure that embedded document indexes are created explicitly"""
-        """
 
         class Rank(EmbeddedDocument):
             title = StringField(required=True)
@@ -192,12 +189,11 @@ class TestIndexes(unittest.TestCase):
         # Indexes are lazy so use list() to perform query
         list(Person.objects)
         info = Person.objects._collection.index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("rank.title", 1)] in info
 
     def test_explicit_geo2d_index(self):
-        """Ensure that geo2d indexes work when created via meta[indexes]
+        """Ensure that geo2d indexes work when created via meta[indexes]"""
-        """
 
         class Place(Document):
             location = DictField()
@@ -207,12 +203,11 @@ class TestIndexes(unittest.TestCase):
 
         Place.ensure_indexes()
         info = Place._get_collection().index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("location.point", "2d")] in info
 
     def test_explicit_geo2d_index_embedded(self):
-        """Ensure that geo2d indexes work when created via meta[indexes]
+        """Ensure that geo2d indexes work when created via meta[indexes]"""
-        """
 
         class EmbeddedLocation(EmbeddedDocument):
             location = DictField()
@@ -227,12 +222,11 @@ class TestIndexes(unittest.TestCase):
 
         Place.ensure_indexes()
         info = Place._get_collection().index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("current.location.point", "2d")] in info
 
     def test_explicit_geosphere_index(self):
-        """Ensure that geosphere indexes work when created via meta[indexes]
+        """Ensure that geosphere indexes work when created via meta[indexes]"""
-        """
 
         class Place(Document):
             location = DictField()
@@ -244,12 +238,11 @@ class TestIndexes(unittest.TestCase):
 
         Place.ensure_indexes()
         info = Place._get_collection().index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("location.point", "2dsphere")] in info
 
     def test_explicit_geohaystack_index(self):
-        """Ensure that geohaystack indexes work when created via meta[indexes]
+        """Ensure that geohaystack indexes work when created via meta[indexes]"""
-        """
         pytest.skip(
             "GeoHaystack index creation is not supported for now"
             "from meta, as it requires a bucketSize parameter."
@@ -266,12 +259,11 @@ class TestIndexes(unittest.TestCase):
 
         Place.ensure_indexes()
         info = Place._get_collection().index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("location.point", "geoHaystack")] in info
 
     def test_create_geohaystack_index(self):
-        """Ensure that geohaystack indexes can be created
+        """Ensure that geohaystack indexes can be created"""
-        """
 
         class Place(Document):
             location = DictField()
@@ -279,7 +271,7 @@ class TestIndexes(unittest.TestCase):
 
         Place.create_index({"fields": (")location.point", "name")}, bucketSize=10)
         info = Place._get_collection().index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("location.point", "geoHaystack"), ("name", 1)] in info
 
     def test_dictionary_indexes(self):
@@ -308,7 +300,7 @@ class TestIndexes(unittest.TestCase):
         info = BlogPost.objects._collection.index_information()
         info = [
             (value["key"], value.get("unique", False), value.get("sparse", False))
-            for key, value in iteritems(info)
+            for key, value in info.items()
         ]
         assert ([("addDate", -1)], True, True) in info
 
@@ -366,8 +358,7 @@ class TestIndexes(unittest.TestCase):
         assert sorted(info.keys()) == ["_cls_1_user_guid_1", "_id_"]
 
     def test_embedded_document_index(self):
-        """Tests settings an index on an embedded document
+        """Tests settings an index on an embedded document"""
-        """
 
         class Date(EmbeddedDocument):
             year = IntField(db_field="yr")
@@ -384,8 +375,7 @@ class TestIndexes(unittest.TestCase):
         assert sorted(info.keys()) == ["_id_", "date.yr_-1"]
 
     def test_list_embedded_document_index(self):
-        """Ensure list embedded documents can be indexed
+        """Ensure list embedded documents can be indexed"""
-        """
 
         class Tag(EmbeddedDocument):
             name = StringField(db_field="tag")
@@ -421,8 +411,7 @@ class TestIndexes(unittest.TestCase):
         assert sorted(info.keys()) == ["_cls_1", "_id_"]
 
     def test_covered_index(self):
-        """Ensure that covered indexes can be used
+        """Ensure that covered indexes can be used"""
-        """
 
         class Test(Document):
             a = IntField()
@@ -552,15 +541,15 @@ class TestIndexes(unittest.TestCase):
         assert 5 == query_result.count()
 
         incorrect_collation = {"arndom": "wrdo"}
-        with pytest.raises(OperationFailure):
+        with pytest.raises(OperationFailure) as exc_info:
             BlogPost.objects.collation(incorrect_collation).count()
+        assert "Missing expected field" in str(exc_info.value)
 
         query_result = BlogPost.objects.collation({}).order_by("name")
         assert [x.name for x in query_result] == sorted(names)
 
     def test_unique(self):
-        """Ensure that uniqueness constraints are applied to fields.
+        """Ensure that uniqueness constraints are applied to fields."""
-        """
 
         class BlogPost(Document):
             title = StringField()
@@ -608,8 +597,7 @@ class TestIndexes(unittest.TestCase):
         )
 
     def test_unique_with(self):
-        """Ensure that unique_with constraints are applied to fields.
+        """Ensure that unique_with constraints are applied to fields."""
-        """
 
         class Date(EmbeddedDocument):
             year = IntField(db_field="yr")
@@ -634,8 +622,7 @@ class TestIndexes(unittest.TestCase):
             post3.save()
 
     def test_unique_embedded_document(self):
-        """Ensure that uniqueness constraints are applied to fields on embedded documents.
+        """Ensure that uniqueness constraints are applied to fields on embedded documents."""
-        """
 
         class SubDocument(EmbeddedDocument):
             year = IntField(db_field="yr")
@@ -806,18 +793,6 @@ class TestIndexes(unittest.TestCase):
         info = Log.objects._collection.index_information()
         assert 3600 == info["created_1"]["expireAfterSeconds"]
 
-    def test_index_drop_dups_silently_ignored(self):
-        class Customer(Document):
-            cust_id = IntField(unique=True, required=True)
-            meta = {
-                "indexes": ["cust_id"],
-                "index_drop_dups": True,
-                "allow_inheritance": False,
-            }
-
-        Customer.drop_collection()
-        Customer.objects.first()
-
     def test_unique_and_indexes(self):
         """Ensure that 'unique' constraints aren't overridden by
         meta.indexes.
@@ -901,7 +876,7 @@ class TestIndexes(unittest.TestCase):
             self.fail("Unbound local error at index + pk definition")
 
         info = BlogPost.objects._collection.index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         index_item = [("_id", 1), ("comments.comment_id", 1)]
         assert index_item in info
 
@@ -942,7 +917,7 @@ class TestIndexes(unittest.TestCase):
             meta = {"indexes": ["provider_ids.foo", "provider_ids.bar"]}
 
         info = MyDoc.objects._collection.index_information()
-        info = [value["key"] for key, value in iteritems(info)]
+        info = [value["key"] for key, value in info.items()]
         assert [("provider_ids.foo", 1)] in info
         assert [("provider_ids.bar", 1)] in info
 
@@ -1058,10 +1033,6 @@ class TestIndexes(unittest.TestCase):
                 del index_info[key][
                     "ns"
                 ]  # drop the index namespace - we don't care about that here, MongoDB 3+
-            if "dropDups" in index_info[key]:
-                del index_info[key][
-                    "dropDups"
-                ]  # drop the index dropDups - it is deprecated in MongoDB 3+
 
         assert index_info == {
             "txt_1": {"key": [("txt", 1)], "background": False},

tests/document/test_inheritance.py

@@ -1,9 +1,7 @@
-# -*- coding: utf-8 -*-
 import unittest
 import warnings
 
 import pytest
-from six import iteritems
 
 from mongoengine import (
     BooleanField,
@@ -47,8 +45,7 @@ class TestInheritance(MongoDBTestCase):
         test_doc.delete()
 
     def test_superclasses(self):
-        """Ensure that the correct list of superclasses is assembled.
+        """Ensure that the correct list of superclasses is assembled."""
-        """
 
         class Animal(Document):
             meta = {"allow_inheritance": True}
@@ -218,8 +215,7 @@ class TestInheritance(MongoDBTestCase):
         assert Pike._subclasses == ("Animal.Fish.Pike",)
 
     def test_inheritance_meta_data(self):
-        """Ensure that document may inherit fields from a superclass document.
+        """Ensure that document may inherit fields from a superclass document."""
-        """
 
         class Person(Document):
             name = StringField()
@@ -236,8 +232,7 @@ class TestInheritance(MongoDBTestCase):
         assert Employee._get_collection_name() == Person._get_collection_name()
 
     def test_inheritance_to_mongo_keys(self):
-        """Ensure that document may inherit fields from a superclass document.
+        """Ensure that document may inherit fields from a superclass document."""
-        """
 
         class Person(Document):
             name = StringField()
@@ -261,7 +256,7 @@ class TestInheritance(MongoDBTestCase):
         assert Employee._get_collection_name() == Person._get_collection_name()
 
     def test_indexes_and_multiple_inheritance(self):
-        """ Ensure that all of the indexes are created for a document with
+        """Ensure that all of the indexes are created for a document with
         multiple inheritance.
         """
 
@@ -285,14 +280,11 @@ class TestInheritance(MongoDBTestCase):
         C.ensure_indexes()
 
         assert sorted(
-            [idx["key"] for idx in C._get_collection().index_information().values()]
+            idx["key"] for idx in C._get_collection().index_information().values()
-        ) == sorted(
+        ) == sorted([[("_cls", 1), ("b", 1)], [("_id", 1)], [("_cls", 1), ("a", 1)]])
-            [[(u"_cls", 1), (u"b", 1)], [(u"_id", 1)], [(u"_cls", 1), (u"a", 1)]]
-        )
 
     def test_polymorphic_queries(self):
-        """Ensure that the correct subclasses are returned from a query
+        """Ensure that the correct subclasses are returned from a query"""
-        """
 
         class Animal(Document):
             meta = {"allow_inheritance": True}
@@ -349,8 +341,7 @@ class TestInheritance(MongoDBTestCase):
         assert "_cls" not in obj
 
     def test_cant_turn_off_inheritance_on_subclass(self):
-        """Ensure if inheritance is on in a subclass you cant turn it off.
+        """Ensure if inheritance is on in a subclass you cant turn it off."""
-        """
 
         class Animal(Document):
             name = StringField()
@@ -476,7 +467,7 @@ class TestInheritance(MongoDBTestCase):
         assert city.pk is None
         # TODO: expected error? Shouldn't we create a new error type?
         with pytest.raises(KeyError):
-            setattr(city, "pk", 1)
+            city.pk = 1
 
     def test_allow_inheritance_embedded_document(self):
         """Ensure embedded documents respect inheritance."""
@@ -500,8 +491,7 @@ class TestInheritance(MongoDBTestCase):
         assert "_cls" in doc.to_mongo()
 
     def test_document_inheritance(self):
-        """Ensure mutliple inheritance of abstract documents
+        """Ensure mutliple inheritance of abstract documents"""
-        """
 
         class DateCreatedDocument(Document):
             meta = {"allow_inheritance": True, "abstract": True}
@@ -509,13 +499,8 @@ class TestInheritance(MongoDBTestCase):
         class DateUpdatedDocument(Document):
             meta = {"allow_inheritance": True, "abstract": True}
 
-        try:
+        class MyDocument(DateCreatedDocument, DateUpdatedDocument):
-
+            pass
-            class MyDocument(DateCreatedDocument, DateUpdatedDocument):
-                pass
-
-        except Exception:
-            assert False, "Couldn't create MyDocument class"
 
     def test_abstract_documents(self):
         """Ensure that a document superclass can be marked as abstract
@@ -523,7 +508,6 @@ class TestInheritance(MongoDBTestCase):
 
         defaults = {
             "index_background": True,
-            "index_drop_dups": True,
             "index_opts": {"hello": "world"},
             "allow_inheritance": True,
             "queryset_class": "QuerySet",
@@ -550,7 +534,7 @@ class TestInheritance(MongoDBTestCase):
         class Human(Mammal):
             pass
 
-        for k, v in iteritems(defaults):
+        for k, v in defaults.items():
             for cls in [Animal, Fish, Guppy]:
                 assert cls._meta[k] == v
 

tests/document/test_instance.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import os
 import pickle
 import unittest
@@ -10,7 +9,6 @@ import bson
 from bson import DBRef, ObjectId
 from pymongo.errors import DuplicateKeyError
 import pytest
-from six import iteritems
 
 from mongoengine import *
 from mongoengine import signals
@@ -162,8 +160,7 @@ class TestDocumentInstance(MongoDBTestCase):
         Log.objects
 
     def test_repr(self):
-        """Ensure that unicode representation works
+        """Ensure that unicode representation works"""
-        """
 
         class Article(Document):
             title = StringField()
@@ -171,7 +168,7 @@ class TestDocumentInstance(MongoDBTestCase):
             def __unicode__(self):
                 return self.title
 
-        doc = Article(title=u"привет мир")
+        doc = Article(title="привет мир")
 
         assert "<Article: привет мир>" == repr(doc)
 
@@ -184,12 +181,12 @@ class TestDocumentInstance(MongoDBTestCase):
             def __str__(self):
                 return None
 
-        doc = Article(title=u"привет мир")
+        doc = Article(title="привет мир")
         assert "<Article: None>" == repr(doc)
 
     def test_queryset_resurrects_dropped_collection(self):
         self.Person.drop_collection()
-        assert [] == list(self.Person.objects())
+        assert list(self.Person.objects()) == []
 
         # Ensure works correctly with inhertited classes
         class Actor(self.Person):
@@ -197,7 +194,7 @@ class TestDocumentInstance(MongoDBTestCase):
 
         Actor.objects()
         self.Person.drop_collection()
-        assert [] == list(Actor.objects())
+        assert list(Actor.objects()) == []
 
     def test_polymorphic_references(self):
         """Ensure that the correct subclasses are returned from a query
@@ -502,7 +499,7 @@ class TestDocumentInstance(MongoDBTestCase):
         doc.reload()
         Animal.drop_collection()
 
-    def test_update_shard_key_routing(self):
+    def test_save_update_shard_key_routing(self):
         """Ensures updating a doc with a specified shard_key includes it in
         the query.
         """
@@ -524,9 +521,32 @@ class TestDocumentInstance(MongoDBTestCase):
             query_op = q.db.system.profile.find({"ns": "mongoenginetest.animal"})[0]
             assert query_op["op"] == "update"
             if mongo_db <= MONGODB_34:
-                assert set(query_op["query"].keys()) == set(["_id", "is_mammal"])
+                assert set(query_op["query"].keys()) == {"_id", "is_mammal"}
             else:
-                assert set(query_op["command"]["q"].keys()) == set(["_id", "is_mammal"])
+                assert set(query_op["command"]["q"].keys()) == {"_id", "is_mammal"}
+
+        Animal.drop_collection()
+
+    def test_save_create_shard_key_routing(self):
+        """Ensures inserting a doc with a specified shard_key includes it in
+        the query.
+        """
+
+        class Animal(Document):
+            _id = UUIDField(binary=False, primary_key=True, default=uuid.uuid4)
+            is_mammal = BooleanField()
+            name = StringField()
+            meta = {"shard_key": ("is_mammal",)}
+
+        Animal.drop_collection()
+        doc = Animal(is_mammal=True, name="Dog")
+
+        with query_counter() as q:
+            doc.save()
+            query_op = q.db.system.profile.find({"ns": "mongoenginetest.animal"})[0]
+            assert query_op["op"] == "command"
+            assert query_op["command"]["findAndModify"] == "animal"
+            assert set(query_op["command"]["query"].keys()) == {"_id", "is_mammal"}
 
         Animal.drop_collection()
 
@@ -579,7 +599,8 @@ class TestDocumentInstance(MongoDBTestCase):
         doc.embedded_field.list_field.append(1)
         doc.embedded_field.dict_field["woot"] = "woot"
 
-        assert doc._get_changed_fields() == [
+        changed = doc._get_changed_fields()
+        assert changed == [
             "list_field",
             "dict_field.woot",
             "embedded_field.list_field",
@@ -1407,15 +1428,15 @@ class TestDocumentInstance(MongoDBTestCase):
         coll = self.Person._get_collection()
         doc = self.Person(name="John").save()
         raw_doc = coll.find_one({"_id": doc.pk})
-        assert set(raw_doc.keys()) == set(["_id", "_cls", "name"])
+        assert set(raw_doc.keys()) == {"_id", "_cls", "name"}
 
         doc.update(rename__name="first_name")
         raw_doc = coll.find_one({"_id": doc.pk})
-        assert set(raw_doc.keys()) == set(["_id", "_cls", "first_name"])
+        assert set(raw_doc.keys()) == {"_id", "_cls", "first_name"}
         assert raw_doc["first_name"] == "John"
 
     def test_inserts_if_you_set_the_pk(self):
-        p1 = self.Person(name="p1", id=bson.ObjectId()).save()
+        _ = self.Person(name="p1", id=bson.ObjectId()).save()
         p2 = self.Person(name="p2")
         p2.id = bson.ObjectId()
         p2.save()
@@ -1531,8 +1552,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert site.page.log_message == "Error: Dummy message"
 
     def test_update_list_field(self):
-        """Test update on `ListField` with $pull + $in.
+        """Test update on `ListField` with $pull + $in."""
-        """
 
         class Doc(Document):
             foo = ListField(StringField())
@@ -2021,7 +2041,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert promoted_employee.details is None
 
     def test_object_mixins(self):
-        class NameMixin(object):
+        class NameMixin:
             name = StringField()
 
         class Foo(EmbeddedDocument, NameMixin):
@@ -2035,7 +2055,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert ["id", "name", "widgets"] == sorted(Bar._fields.keys())
 
     def test_mixin_inheritance(self):
-        class BaseMixIn(object):
+        class BaseMixIn:
             count = IntField()
             data = StringField()
 
@@ -2196,7 +2216,7 @@ class TestDocumentInstance(MongoDBTestCase):
 
         user = User(name="Mike").save()
         reviewer = User(name="John").save()
-        book = Book(author=user, reviewer=reviewer).save()
+        _ = Book(author=user, reviewer=reviewer).save()
 
         reviewer.delete()
         assert Book.objects.count() == 1
@@ -2222,7 +2242,7 @@ class TestDocumentInstance(MongoDBTestCase):
 
         user_1 = User(id=1).save()
         user_2 = User(id=2).save()
-        book_1 = Book(id=1, author=user_2).save()
+        _ = Book(id=1, author=user_2).save()
         book_2 = Book(id=2, author=user_1).save()
 
         user_2.delete()
@@ -2231,7 +2251,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert Book.objects.get() == book_2
 
         user_3 = User(id=3).save()
-        book_3 = Book(id=3, author=user_3).save()
+        _ = Book(id=3, author=user_3).save()
 
         user_3.delete()
         # Deleting user_3 should also delete book_3
@@ -2794,15 +2814,13 @@ class TestDocumentInstance(MongoDBTestCase):
         register_connection("testdb-2", "mongoenginetest2")
 
         class A(Document):
-            """Uses default db_alias
+            """Uses default db_alias"""
-            """
 
             name = StringField()
             meta = {"allow_inheritance": True}
 
         class B(A):
-            """Uses testdb-2 db_alias
+            """Uses testdb-2 db_alias"""
-            """
 
             meta = {"db_alias": "testdb-2"}
 
@@ -2882,50 +2900,32 @@ class TestDocumentInstance(MongoDBTestCase):
         # Checks
         assert ",".join([str(b) for b in Book.objects.all()]) == "1,2,3,4,5,6,7,8,9"
         # bob related books
-        assert (
+        bob_books_qs = Book.objects.filter(
-            ",".join(
+            Q(extra__a=bob) | Q(author=bob) | Q(extra__b=bob)
-                [
-                    str(b)
-                    for b in Book.objects.filter(
-                        Q(extra__a=bob) | Q(author=bob) | Q(extra__b=bob)
-                    )
-                ]
-            )
-            == "1,2,3,4"
         )
+        assert [str(b) for b in bob_books_qs] == ["1", "2", "3", "4"]
+        assert bob_books_qs.count() == 4
 
         # Susan & Karl related books
-        assert (
+        susan_karl_books_qs = Book.objects.filter(
-            ",".join(
+            Q(extra__a__all=[karl, susan])
-                [
+            | Q(author__all=[karl, susan])
-                    str(b)
+            | Q(extra__b__all=[karl.to_dbref(), susan.to_dbref()])
-                    for b in Book.objects.filter(
-                        Q(extra__a__all=[karl, susan])
-                        | Q(author__all=[karl, susan])
-                        | Q(extra__b__all=[karl.to_dbref(), susan.to_dbref()])
-                    )
-                ]
-            )
-            == "1"
         )
+        assert [str(b) for b in susan_karl_books_qs] == ["1"]
+        assert susan_karl_books_qs.count() == 1
 
         # $Where
-        assert (
+        custom_qs = Book.objects.filter(
-            u",".join(
+            __raw__={
-                [
+                "$where": """
-                    str(b)
-                    for b in Book.objects.filter(
-                        __raw__={
-                            "$where": """
                                             function(){
                                                 return this.name == '1' ||
                                                        this.name == '2';}"""
-                        }
+            }
-                    )
-                ]
-            )
-            == "1,2"
         )
+        assert [str(b) for b in custom_qs] == ["1", "2"]
+        assert custom_qs.count() == 2
 
     def test_switch_db_instance(self):
         register_connection("testdb-1", "mongoenginetest2")
@@ -3205,7 +3205,7 @@ class TestDocumentInstance(MongoDBTestCase):
     def test_positional_creation(self):
         """Document cannot be instantiated using positional arguments."""
         with pytest.raises(TypeError) as exc_info:
-            person = self.Person("Test User", 42)
+            self.Person("Test User", 42)
 
         expected_msg = (
             "Instantiating a document with positional arguments is not "
@@ -3274,7 +3274,7 @@ class TestDocumentInstance(MongoDBTestCase):
 
             def expand(self):
                 self.flattened_parameter = {}
-                for parameter_name, parameter in iteritems(self.parameters):
+                for parameter_name, parameter in self.parameters.items():
                     parameter.expand()
 
         class NodesSystem(Document):
@@ -3282,10 +3282,10 @@ class TestDocumentInstance(MongoDBTestCase):
             nodes = MapField(ReferenceField(Node, dbref=False))
 
             def save(self, *args, **kwargs):
-                for node_name, node in iteritems(self.nodes):
+                for node_name, node in self.nodes.items():
                     node.expand()
                     node.save(*args, **kwargs)
-                super(NodesSystem, self).save(*args, **kwargs)
+                super().save(*args, **kwargs)
 
         NodesSystem.drop_collection()
         Node.drop_collection()
@@ -3412,7 +3412,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert obj3 != dbref2
         assert dbref2 != obj3
 
-    def test_default_values(self):
+    def test_default_values_dont_get_override_upon_save_when_only_is_used(self):
         class Person(Document):
             created_on = DateTimeField(default=lambda: datetime.utcnow())
             name = StringField()
@@ -3590,8 +3590,7 @@ class TestDocumentInstance(MongoDBTestCase):
         assert u_from_db.height is None
 
     def test_not_saved_eq(self):
-        """Ensure we can compare documents not saved.
+        """Ensure we can compare documents not saved."""
-        """
 
         class Person(Document):
             pass
@@ -3607,13 +3606,13 @@ class TestDocumentInstance(MongoDBTestCase):
             v = StringField()
 
         class A(Document):
-            l = ListField(EmbeddedDocumentField(B))
+            array = ListField(EmbeddedDocumentField(B))
 
         A.objects.delete()
-        A(l=[B(v="1"), B(v="2"), B(v="3")]).save()
+        A(array=[B(v="1"), B(v="2"), B(v="3")]).save()
         a = A.objects.get()
-        assert a.l._instance == a
+        assert a.array._instance == a
-        for idx, b in enumerate(a.l):
+        for idx, b in enumerate(a.array):
             assert b._instance == a
         assert idx == 2
 
@@ -3735,7 +3734,7 @@ class TestDocumentInstance(MongoDBTestCase):
         _ = list(Jedi.objects)  # Ensure a proper document loads without errors
 
         # Forces a document with a wrong shape (may occur in case of migration)
-        value = u"I_should_be_a_dict"
+        value = "I_should_be_a_dict"
         coll.insert_one({"light_saber": value})
 
         with pytest.raises(InvalidDocumentError) as exc_info:
@@ -3800,5 +3799,95 @@ class ObjectKeyTestCase(MongoDBTestCase):
         assert book._object_key == {"pk": book.pk, "author__name": "Author"}
 
 
+class DBFieldMappingTest(MongoDBTestCase):
+    def setUp(self):
+        class Fields:
+            w1 = BooleanField(db_field="w2")
+
+            x1 = BooleanField(db_field="x2")
+            x2 = BooleanField(db_field="x3")
+
+            y1 = BooleanField(db_field="y0")
+            y2 = BooleanField(db_field="y1")
+
+            z1 = BooleanField(db_field="z2")
+            z2 = BooleanField(db_field="z1")
+
+        class Doc(Fields, Document):
+            pass
+
+        class DynDoc(Fields, DynamicDocument):
+            pass
+
+        self.Doc = Doc
+        self.DynDoc = DynDoc
+
+    def tearDown(self):
+        for collection in list_collection_names(self.db):
+            self.db.drop_collection(collection)
+
+    def test_setting_fields_in_constructor_of_strict_doc_uses_model_names(self):
+        doc = self.Doc(z1=True, z2=False)
+        assert doc.z1 is True
+        assert doc.z2 is False
+
+    def test_setting_fields_in_constructor_of_dyn_doc_uses_model_names(self):
+        doc = self.DynDoc(z1=True, z2=False)
+        assert doc.z1 is True
+        assert doc.z2 is False
+
+    def test_setting_unknown_field_in_constructor_of_dyn_doc_does_not_overwrite_model_fields(
+        self,
+    ):
+        doc = self.DynDoc(w2=True)
+        assert doc.w1 is None
+        assert doc.w2 is True
+
+    def test_unknown_fields_of_strict_doc_do_not_overwrite_dbfields_1(self):
+        doc = self.Doc()
+        doc.w2 = True
+        doc.x3 = True
+        doc.y0 = True
+        doc.save()
+        reloaded = self.Doc.objects.get(id=doc.id)
+        assert reloaded.w1 is None
+        assert reloaded.x1 is None
+        assert reloaded.x2 is None
+        assert reloaded.y1 is None
+        assert reloaded.y2 is None
+
+    def test_dbfields_are_loaded_to_the_right_modelfield_for_strict_doc_2(self):
+        doc = self.Doc()
+        doc.x2 = True
+        doc.y2 = True
+        doc.z2 = True
+        doc.save()
+        reloaded = self.Doc.objects.get(id=doc.id)
+        assert (
+            reloaded.x1,
+            reloaded.x2,
+            reloaded.y1,
+            reloaded.y2,
+            reloaded.z1,
+            reloaded.z2,
+        ) == (doc.x1, doc.x2, doc.y1, doc.y2, doc.z1, doc.z2)
+
+    def test_dbfields_are_loaded_to_the_right_modelfield_for_dyn_doc_2(self):
+        doc = self.DynDoc()
+        doc.x2 = True
+        doc.y2 = True
+        doc.z2 = True
+        doc.save()
+        reloaded = self.DynDoc.objects.get(id=doc.id)
+        assert (
+            reloaded.x1,
+            reloaded.x2,
+            reloaded.y1,
+            reloaded.y2,
+            reloaded.z1,
+            reloaded.z2,
+        ) == (doc.x1, doc.x2, doc.y1, doc.y2, doc.z1, doc.z2)
+
+
 if __name__ == "__main__":
     unittest.main()

tests/document/test_validation.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import unittest
 from datetime import datetime
 
@@ -10,8 +9,7 @@ from tests.utils import MongoDBTestCase
 
 class TestValidatorError(MongoDBTestCase):
     def test_to_dict(self):
-        """Ensure a ValidationError handles error to_dict correctly.
+        """Ensure a ValidationError handles error to_dict correctly."""
-        """
         error = ValidationError("root")
         assert error.to_dict() == {}
 
@@ -91,8 +89,7 @@ class TestValidatorError(MongoDBTestCase):
             p.validate()
 
     def test_embedded_document_validation(self):
-        """Ensure that embedded documents may be validated.
+        """Ensure that embedded documents may be validated."""
-        """
 
         class Comment(EmbeddedDocument):
             date = DateTimeField()
@@ -213,10 +210,7 @@ class TestValidatorError(MongoDBTestCase):
         child.reference = parent
 
         # Saving the child should not raise a ValidationError
-        try:
+        child.save()
-            child.save()
-        except ValidationError as e:
-            self.fail("ValidationError raised: %s" % e.message)
 
 
 if __name__ == "__main__":

tests/fields/test_binary_field.py

@@ -1,28 +1,25 @@
-# -*- coding: utf-8 -*-
 import uuid
 
 from bson import Binary
 import pytest
-import six
 
 from mongoengine import *
 from tests.utils import MongoDBTestCase
 
-BIN_VALUE = six.b(
+BIN_VALUE = "\xa9\xf3\x8d(\xd7\x03\x84\xb4k[\x0f\xe3\xa2\x19\x85p[J\xa3\xd2>\xde\xe6\x87\xb1\x7f\xc6\xe6\xd9r\x18\xf5".encode(
-    "\xa9\xf3\x8d(\xd7\x03\x84\xb4k[\x0f\xe3\xa2\x19\x85p[J\xa3\xd2>\xde\xe6\x87\xb1\x7f\xc6\xe6\xd9r\x18\xf5"
+    "latin-1"
 )
 
 
 class TestBinaryField(MongoDBTestCase):
     def test_binary_fields(self):
-        """Ensure that binary fields can be stored and retrieved.
+        """Ensure that binary fields can be stored and retrieved."""
-        """
 
         class Attachment(Document):
             content_type = StringField()
             blob = BinaryField()
 
-        BLOB = six.b("\xe6\x00\xc4\xff\x07")
+        BLOB = b"\xe6\x00\xc4\xff\x07"
         MIME_TYPE = "application/octet-stream"
 
         Attachment.drop_collection()
@@ -32,11 +29,10 @@ class TestBinaryField(MongoDBTestCase):
 
         attachment_1 = Attachment.objects().first()
         assert MIME_TYPE == attachment_1.content_type
-        assert BLOB == six.binary_type(attachment_1.blob)
+        assert BLOB == bytes(attachment_1.blob)
 
     def test_validation_succeeds(self):
-        """Ensure that valid values can be assigned to binary fields.
+        """Ensure that valid values can be assigned to binary fields."""
-        """
 
         class AttachmentRequired(Document):
             blob = BinaryField(required=True)
@@ -47,11 +43,11 @@ class TestBinaryField(MongoDBTestCase):
         attachment_required = AttachmentRequired()
         with pytest.raises(ValidationError):
             attachment_required.validate()
-        attachment_required.blob = Binary(six.b("\xe6\x00\xc4\xff\x07"))
+        attachment_required.blob = Binary(b"\xe6\x00\xc4\xff\x07")
         attachment_required.validate()
 
-        _5_BYTES = six.b("\xe6\x00\xc4\xff\x07")
+        _5_BYTES = b"\xe6\x00\xc4\xff\x07"
-        _4_BYTES = six.b("\xe6\x00\xc4\xff")
+        _4_BYTES = b"\xe6\x00\xc4\xff"
         with pytest.raises(ValidationError):
             AttachmentSizeLimit(blob=_5_BYTES).validate()
         AttachmentSizeLimit(blob=_4_BYTES).validate()
@@ -62,7 +58,7 @@ class TestBinaryField(MongoDBTestCase):
         class Attachment(Document):
             blob = BinaryField()
 
-        for invalid_data in (2, u"Im_a_unicode", ["some_str"]):
+        for invalid_data in (2, "Im_a_unicode", ["some_str"]):
             with pytest.raises(ValidationError):
                 Attachment(blob=invalid_data).validate()
 
@@ -123,10 +119,7 @@ class TestBinaryField(MongoDBTestCase):
             upsert=True, new=True, set__bin_field=BIN_VALUE
         )
         assert doc.some_field == "test"
-        if six.PY3:
+        assert doc.bin_field == BIN_VALUE
-            assert doc.bin_field == BIN_VALUE
-        else:
-            assert doc.bin_field == Binary(BIN_VALUE)
 
     def test_update_one(self):
         """Ensures no regression of bug #1127"""
@@ -136,7 +129,7 @@ class TestBinaryField(MongoDBTestCase):
 
         MyDocument.drop_collection()
 
-        bin_data = six.b("\xe6\x00\xc4\xff\x07")
+        bin_data = b"\xe6\x00\xc4\xff\x07"
         doc = MyDocument(bin_field=bin_data).save()
 
         n_updated = MyDocument.objects(bin_field=bin_data).update_one(
@@ -144,7 +137,4 @@ class TestBinaryField(MongoDBTestCase):
         )
         assert n_updated == 1
         fetched = MyDocument.objects.with_id(doc.id)
-        if six.PY3:
+        assert fetched.bin_field == BIN_VALUE
-            assert fetched.bin_field == BIN_VALUE
-        else:
-            assert fetched.bin_field == Binary(BIN_VALUE)

tests/fields/test_boolean_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from mongoengine import *

tests/fields/test_cached_reference_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from decimal import Decimal
 
 import pytest
@@ -191,9 +190,9 @@ class TestCachedReferenceField(MongoDBTestCase):
 
         assert dict(a2.to_mongo()) == {
             "_id": a2.pk,
-            "name": u"Wilson Junior",
+            "name": "Wilson Junior",
-            "tp": u"pf",
+            "tp": "pf",
-            "father": {"_id": a1.pk, "tp": u"pj"},
+            "father": {"_id": a1.pk, "tp": "pj"},
         }
 
         assert Person.objects(father=a1)._query == {"father._id": a1.pk}
@@ -205,9 +204,9 @@ class TestCachedReferenceField(MongoDBTestCase):
         a2.reload()
         assert dict(a2.to_mongo()) == {
             "_id": a2.pk,
-            "name": u"Wilson Junior",
+            "name": "Wilson Junior",
-            "tp": u"pf",
+            "tp": "pf",
-            "father": {"_id": a1.pk, "tp": u"pf"},
+            "father": {"_id": a1.pk, "tp": "pf"},
         }
 
     def test_cached_reference_fields_on_embedded_documents(self):

tests/fields/test_complex_datetime_field.py

@@ -1,9 +1,10 @@
-# -*- coding: utf-8 -*-
 import datetime
 import itertools
 import math
 import re
 
+import pytest
+
 from mongoengine import *
 
 from tests.utils import MongoDBTestCase
@@ -59,13 +60,13 @@ class ComplexDateTimeFieldTest(MongoDBTestCase):
             assert log == log1
 
         # Test string padding
-        microsecond = map(int, [math.pow(10, x) for x in range(6)])
+        microsecond = map(int, (math.pow(10, x) for x in range(6)))
         mm = dd = hh = ii = ss = [1, 10]
 
         for values in itertools.product([2014], mm, dd, hh, ii, ss, microsecond):
             stored = LogEntry(date=datetime.datetime(*values)).to_mongo()["date"]
             assert (
-                re.match("^\d{4},\d{2},\d{2},\d{2},\d{2},\d{2},\d{6}$", stored)
+                re.match(r"^\d{4},\d{2},\d{2},\d{2},\d{2},\d{2},\d{6}$", stored)
                 is not None
             )
 
@@ -74,7 +75,7 @@ class ComplexDateTimeFieldTest(MongoDBTestCase):
             "date_with_dots"
         ]
         assert (
-            re.match("^\d{4}.\d{2}.\d{2}.\d{2}.\d{2}.\d{2}.\d{6}$", stored) is not None
+            re.match(r"^\d{4}.\d{2}.\d{2}.\d{2}.\d{2}.\d{2}.\d{6}$", stored) is not None
         )
 
     def test_complexdatetime_usage(self):
@@ -191,3 +192,18 @@ class ComplexDateTimeFieldTest(MongoDBTestCase):
 
         fetched_log = Log.objects.with_id(log.id)
         assert fetched_log.timestamp >= NOW
+
+    def test_setting_bad_value_does_not_raise_unless_validate_is_called(self):
+        # test regression of #2253
+
+        class Log(Document):
+            timestamp = ComplexDateTimeField()
+
+        Log.drop_collection()
+
+        log = Log(timestamp="garbage")
+        with pytest.raises(ValidationError):
+            log.validate()
+
+        with pytest.raises(ValidationError):
+            log.save()

tests/fields/test_date_field.py

@@ -1,8 +1,6 @@
-# -*- coding: utf-8 -*-
 import datetime
 
 import pytest
-import six
 
 try:
     import dateutil
@@ -89,17 +87,6 @@ class TestDateField(MongoDBTestCase):
         assert log.date == d1.date()
         assert log.date == d2.date()
 
-        if not six.PY3:
-            # Pre UTC dates microseconds below 1000 are dropped
-            # This does not seem to be true in PY3
-            d1 = datetime.datetime(1969, 12, 31, 23, 59, 59, 999)
-            d2 = datetime.datetime(1969, 12, 31, 23, 59, 59)
-            log.date = d1
-            log.save()
-            log.reload()
-            assert log.date == d1.date()
-            assert log.date == d2.date()
-
     def test_regular_usage(self):
         """Tests for regular datetime fields"""
 

tests/fields/test_datetime_field.py

@@ -1,8 +1,6 @@
-# -*- coding: utf-8 -*-
 import datetime as dt
 
 import pytest
-import six
 
 try:
     import dateutil
@@ -98,17 +96,6 @@ class TestDateTimeField(MongoDBTestCase):
         assert log.date != d1
         assert log.date == d2
 
-        if not six.PY3:
-            # Pre UTC dates microseconds below 1000 are dropped
-            # This does not seem to be true in PY3
-            d1 = dt.datetime(1969, 12, 31, 23, 59, 59, 999)
-            d2 = dt.datetime(1969, 12, 31, 23, 59, 59)
-            log.date = d1
-            log.save()
-            log.reload()
-            assert log.date != d1
-            assert log.date == d2
-
     def test_regular_usage(self):
         """Tests for regular datetime fields"""
 
@@ -213,7 +200,7 @@ class TestDateTimeField(MongoDBTestCase):
         # make sure that passing a parsable datetime works
         dtd = DTDoc()
         dtd.date = date_str
-        assert isinstance(dtd.date, six.string_types)
+        assert isinstance(dtd.date, str)
         dtd.save()
         dtd.reload()
 

tests/fields/test_decimal_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from decimal import Decimal
 
 import pytest
@@ -9,8 +8,7 @@ from tests.utils import MongoDBTestCase
 
 class TestDecimalField(MongoDBTestCase):
     def test_validation(self):
-        """Ensure that invalid values cannot be assigned to decimal fields.
+        """Ensure that invalid values cannot be assigned to decimal fields."""
-        """
 
         class Person(Document):
             height = DecimalField(min_value=Decimal("0.1"), max_value=Decimal("3.5"))

tests/fields/test_dict_field.py

@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+from bson import InvalidDocument
 import pytest
 
 from mongoengine import *
@@ -19,22 +19,24 @@ class TestDictField(MongoDBTestCase):
         post = BlogPost(info=info).save()
         assert get_as_pymongo(post) == {"_id": post.id, "info": info}
 
-    def test_general_things(self):
+    def test_validate_invalid_type(self):
-        """Ensure that dict types work as expected."""
+        class BlogPost(Document):
+            info = DictField()
 
+        BlogPost.drop_collection()
+
+        invalid_infos = ["my post", ["test", "test"], {1: "test"}]
+        for invalid_info in invalid_infos:
+            with pytest.raises(ValidationError):
+                BlogPost(info=invalid_info).validate()
+
+    def test_keys_with_dots_or_dollars(self):
         class BlogPost(Document):
             info = DictField()
 
         BlogPost.drop_collection()
 
         post = BlogPost()
-        post.info = "my post"
-        with pytest.raises(ValidationError):
-            post.validate()
-
-        post.info = ["test", "test"]
-        with pytest.raises(ValidationError):
-            post.validate()
 
         post.info = {"$title": "test"}
         with pytest.raises(ValidationError):
@@ -48,25 +50,34 @@ class TestDictField(MongoDBTestCase):
         with pytest.raises(ValidationError):
             post.validate()
 
-        post.info = {1: "test"}
-        with pytest.raises(ValidationError):
-            post.validate()
-
         post.info = {"nested": {"the.title": "test"}}
         if get_mongodb_version() < MONGODB_36:
-            with pytest.raises(ValidationError):
+            # MongoDB < 3.6 rejects dots
-                post.validate()
+            # To avoid checking the mongodb version from the DictField class
+            # we rely on MongoDB to reject the data during the save
+            post.validate()
+            with pytest.raises(InvalidDocument):
+                post.save()
         else:
             post.validate()
 
         post.info = {"dollar_and_dot": {"te$st.test": "test"}}
         if get_mongodb_version() < MONGODB_36:
-            with pytest.raises(ValidationError):
+            post.validate()
-                post.validate()
+            with pytest.raises(InvalidDocument):
+                post.save()
         else:
             post.validate()
 
-        post.info = {"title": "test"}
+    def test_general_things(self):
+        """Ensure that dict types work as expected."""
+
+        class BlogPost(Document):
+            info = DictField()
+
+        BlogPost.drop_collection()
+
+        post = BlogPost(info={"title": "test"})
         post.save()
 
         post = BlogPost()
@@ -101,7 +112,7 @@ class TestDictField(MongoDBTestCase):
         post.info.setdefault("authors", [])
         post.save()
         post.reload()
-        assert [] == post.info["authors"]
+        assert post.info["authors"] == []
 
     def test_dictfield_dump_document(self):
         """Ensure a DictField can handle another document's dump."""

tests/fields/test_email_field.py

@@ -1,9 +1,6 @@
-# -*- coding: utf-8 -*-
-import sys
-
 import pytest
 
-from mongoengine import *
+from mongoengine import Document, EmailField, ValidationError
 from tests.utils import MongoDBTestCase
 
 
@@ -31,11 +28,11 @@ class TestEmailField(MongoDBTestCase):
             user.validate()
 
         # unicode domain
-        user = User(email=u"user@пример.рф")
+        user = User(email="user@пример.рф")
         user.validate()
 
         # invalid unicode domain
-        user = User(email=u"user@пример")
+        user = User(email="user@пример")
         with pytest.raises(ValidationError):
             user.validate()
 
@@ -49,7 +46,7 @@ class TestEmailField(MongoDBTestCase):
             email = EmailField()
 
         # unicode user shouldn't validate by default...
-        user = User(email=u"Dörte@Sörensen.example.com")
+        user = User(email="Dörte@Sörensen.example.com")
         with pytest.raises(ValidationError):
             user.validate()
 
@@ -57,7 +54,7 @@ class TestEmailField(MongoDBTestCase):
         class User(Document):
             email = EmailField(allow_utf8_user=True)
 
-        user = User(email=u"Dörte@Sörensen.example.com")
+        user = User(email="Dörte@Sörensen.example.com")
         user.validate()
 
     def test_email_field_domain_whitelist(self):

tests/fields/test_embedded_document_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from mongoengine import (
@@ -75,7 +74,7 @@ class TestEmbeddedDocumentField(MongoDBTestCase):
         # Test non exiting attribute
         with pytest.raises(InvalidQueryError) as exc_info:
             Person.objects(settings__notexist="bar").first()
-        assert unicode(exc_info.value) == u'Cannot resolve field "notexist"'
+        assert str(exc_info.value) == 'Cannot resolve field "notexist"'
 
         with pytest.raises(LookUpError):
             Person.objects.only("settings.notexist")
@@ -111,7 +110,7 @@ class TestEmbeddedDocumentField(MongoDBTestCase):
         # Test non exiting attribute
         with pytest.raises(InvalidQueryError) as exc_info:
             assert Person.objects(settings__notexist="bar").first().id == p.id
-        assert unicode(exc_info.value) == u'Cannot resolve field "notexist"'
+        assert str(exc_info.value) == 'Cannot resolve field "notexist"'
 
         # Test existing attribute
         assert Person.objects(settings__base_foo="basefoo").first().id == p.id
@@ -319,7 +318,7 @@ class TestGenericEmbeddedDocumentField(MongoDBTestCase):
         # Test non exiting attribute
         with pytest.raises(InvalidQueryError) as exc_info:
             Person.objects(settings__notexist="bar").first()
-        assert unicode(exc_info.value) == u'Cannot resolve field "notexist"'
+        assert str(exc_info.value) == 'Cannot resolve field "notexist"'
 
         with pytest.raises(LookUpError):
             Person.objects.only("settings.notexist")
@@ -347,7 +346,7 @@ class TestGenericEmbeddedDocumentField(MongoDBTestCase):
         # Test non exiting attribute
         with pytest.raises(InvalidQueryError) as exc_info:
             assert Person.objects(settings__notexist="bar").first().id == p.id
-        assert unicode(exc_info.value) == u'Cannot resolve field "notexist"'
+        assert str(exc_info.value) == 'Cannot resolve field "notexist"'
 
         # Test existing attribute
         assert Person.objects(settings__base_foo="basefoo").first().id == p.id

tests/fields/test_enum_field.py

@@ -0,0 +1,122 @@
+from enum import Enum
+
+from bson import InvalidDocument
+import pytest
+
+from mongoengine import *
+from tests.utils import MongoDBTestCase, get_as_pymongo
+
+
+class Status(Enum):
+    NEW = "new"
+    DONE = "done"
+
+
+class ModelWithEnum(Document):
+    status = EnumField(Status)
+
+
+class TestStringEnumField(MongoDBTestCase):
+    def test_storage(self):
+        model = ModelWithEnum(status=Status.NEW).save()
+        assert get_as_pymongo(model) == {"_id": model.id, "status": "new"}
+
+    def test_set_enum(self):
+        ModelWithEnum.drop_collection()
+        ModelWithEnum(status=Status.NEW).save()
+        assert ModelWithEnum.objects(status=Status.NEW).count() == 1
+        assert ModelWithEnum.objects.first().status == Status.NEW
+
+    def test_set_by_value(self):
+        ModelWithEnum.drop_collection()
+        ModelWithEnum(status="new").save()
+        assert ModelWithEnum.objects.first().status == Status.NEW
+
+    def test_filter(self):
+        ModelWithEnum.drop_collection()
+        ModelWithEnum(status="new").save()
+        assert ModelWithEnum.objects(status="new").count() == 1
+        assert ModelWithEnum.objects(status=Status.NEW).count() == 1
+        assert ModelWithEnum.objects(status=Status.DONE).count() == 0
+
+    def test_change_value(self):
+        m = ModelWithEnum(status="new")
+        m.status = Status.DONE
+        m.save()
+        assert m.status == Status.DONE
+
+    def test_set_default(self):
+        class ModelWithDefault(Document):
+            status = EnumField(Status, default=Status.DONE)
+
+        m = ModelWithDefault().save()
+        assert m.status == Status.DONE
+
+    def test_enum_field_can_be_empty(self):
+        ModelWithEnum.drop_collection()
+        m = ModelWithEnum().save()
+        assert m.status is None
+        assert ModelWithEnum.objects()[0].status is None
+        assert ModelWithEnum.objects(status=None).count() == 1
+
+    def test_set_none_explicitly(self):
+        ModelWithEnum.drop_collection()
+        ModelWithEnum(status=None).save()
+        assert ModelWithEnum.objects.first().status is None
+
+    def test_cannot_create_model_with_wrong_enum_value(self):
+        m = ModelWithEnum(status="wrong_one")
+        with pytest.raises(ValidationError):
+            m.validate()
+
+    def test_user_is_informed_when_tries_to_set_choices(self):
+        with pytest.raises(ValueError, match="'choices' can't be set on EnumField"):
+            EnumField(Status, choices=["my", "custom", "options"])
+
+
+class Color(Enum):
+    RED = 1
+    BLUE = 2
+
+
+class ModelWithColor(Document):
+    color = EnumField(Color, default=Color.RED)
+
+
+class TestIntEnumField(MongoDBTestCase):
+    def test_enum_with_int(self):
+        ModelWithColor.drop_collection()
+        m = ModelWithColor().save()
+        assert m.color == Color.RED
+        assert ModelWithColor.objects(color=Color.RED).count() == 1
+        assert ModelWithColor.objects(color=1).count() == 1
+        assert ModelWithColor.objects(color=2).count() == 0
+
+    def test_create_int_enum_by_value(self):
+        model = ModelWithColor(color=2).save()
+        assert model.color == Color.BLUE
+
+    def test_storage_enum_with_int(self):
+        model = ModelWithColor(color=Color.BLUE).save()
+        assert get_as_pymongo(model) == {"_id": model.id, "color": 2}
+
+    def test_validate_model(self):
+        with pytest.raises(ValidationError, match="Value must be one of"):
+            ModelWithColor(color=3).validate()
+
+        with pytest.raises(ValidationError, match="Value must be one of"):
+            ModelWithColor(color="wrong_type").validate()
+
+
+class TestFunkyEnumField(MongoDBTestCase):
+    def test_enum_incompatible_bson_type_fails_during_save(self):
+        class FunkyColor(Enum):
+            YELLOW = object()
+
+        class ModelWithFunkyColor(Document):
+            color = EnumField(FunkyColor)
+
+        m = ModelWithFunkyColor(color=FunkyColor.YELLOW)
+
+        with pytest.raises(InvalidDocument, match="[cC]annot encode object"):
+            m.save()

tests/fields/test_fields.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import datetime
 import unittest
 
@@ -293,7 +292,7 @@ class TestField(MongoDBTestCase):
         HandleNoneFields.drop_collection()
 
         doc = HandleNoneFields()
-        doc.str_fld = u"spam ham egg"
+        doc.str_fld = "spam ham egg"
         doc.int_fld = 42
         doc.flt_fld = 4.2
         doc.com_dt_fld = datetime.datetime.utcnow()
@@ -329,14 +328,14 @@ class TestField(MongoDBTestCase):
         HandleNoneFields.drop_collection()
 
         doc = HandleNoneFields()
-        doc.str_fld = u"spam ham egg"
+        doc.str_fld = "spam ham egg"
         doc.int_fld = 42
         doc.flt_fld = 4.2
         doc.comp_dt_fld = datetime.datetime.utcnow()
         doc.save()
 
         # Unset all the fields
-        HandleNoneFields._get_collection().update(
+        HandleNoneFields._get_collection().update_one(
             {"_id": doc.id},
             {"$unset": {"str_fld": 1, "int_fld": 1, "flt_fld": 1, "comp_dt_fld": 1}},
         )
@@ -427,9 +426,9 @@ class TestField(MongoDBTestCase):
     def test_list_validation(self):
         """Ensure that a list field only accepts lists with valid elements."""
         access_level_choices = (
-            ("a", u"Administration"),
+            ("a", "Administration"),
-            ("b", u"Manager"),
+            ("b", "Manager"),
-            ("c", u"Staff"),
+            ("c", "Staff"),
         )
 
         class User(Document):
@@ -477,7 +476,7 @@ class TestField(MongoDBTestCase):
         post.access_list = ["a", "b"]
         post.validate()
 
-        assert post.get_access_list_display() == u"Administration, Manager"
+        assert post.get_access_list_display() == "Administration, Manager"
 
         post.comments = ["a"]
         with pytest.raises(ValidationError):
@@ -545,8 +544,7 @@ class TestField(MongoDBTestCase):
         post.validate()
 
     def test_sorted_list_sorting(self):
-        """Ensure that a sorted list field properly sorts values.
+        """Ensure that a sorted list field properly sorts values."""
-        """
 
         class Comment(EmbeddedDocument):
             order = IntField()
@@ -662,8 +660,7 @@ class TestField(MongoDBTestCase):
         )
 
     def test_list_field_manipulative_operators(self):
-        """Ensure that ListField works with standard list operators that manipulate the list.
+        """Ensure that ListField works with standard list operators that manipulate the list."""
-        """
 
         class BlogPost(Document):
             ref = StringField()
@@ -1084,7 +1081,7 @@ class TestField(MongoDBTestCase):
 
         e = Simple().save()
         e.mapping = []
-        assert [] == e._changed_fields
+        assert e._changed_fields == []
 
         class Simple(Document):
             mapping = DictField()
@@ -1093,7 +1090,7 @@ class TestField(MongoDBTestCase):
 
         e = Simple().save()
         e.mapping = {}
-        assert [] == e._changed_fields
+        assert e._changed_fields == []
 
     def test_slice_marks_field_as_changed(self):
         class Simple(Document):
@@ -1360,9 +1357,9 @@ class TestField(MongoDBTestCase):
         foo.delete()
         bar = Bar.objects.get()
         with pytest.raises(DoesNotExist):
-            getattr(bar, "ref")
+            bar.ref
         with pytest.raises(DoesNotExist):
-            getattr(bar, "generic_ref")
+            bar.generic_ref
 
         # When auto_dereference is disabled, there is no trouble returning DBRef
         bar = Bar.objects.get()
@@ -1373,8 +1370,7 @@ class TestField(MongoDBTestCase):
         assert bar.generic_ref == {"_ref": expected, "_cls": "Foo"}
 
     def test_list_item_dereference(self):
-        """Ensure that DBRef items in ListFields are dereferenced.
+        """Ensure that DBRef items in ListFields are dereferenced."""
-        """
 
         class User(Document):
             name = StringField()
@@ -1399,8 +1395,7 @@ class TestField(MongoDBTestCase):
         assert group_obj.members[1].name == user2.name
 
     def test_recursive_reference(self):
-        """Ensure that ReferenceFields can reference their own documents.
+        """Ensure that ReferenceFields can reference their own documents."""
-        """
 
         class Employee(Document):
             name = StringField()
@@ -1427,8 +1422,7 @@ class TestField(MongoDBTestCase):
         assert peter.friends == friends
 
     def test_recursive_embedding(self):
-        """Ensure that EmbeddedDocumentFields can contain their own documents.
+        """Ensure that EmbeddedDocumentFields can contain their own documents."""
-        """
 
         class TreeNode(EmbeddedDocument):
             name = StringField()
@@ -1504,8 +1498,7 @@ class TestField(MongoDBTestCase):
             AbstractDoc.drop_collection()
 
     def test_reference_class_with_abstract_parent(self):
-        """Ensure that a class with an abstract parent can be referenced.
+        """Ensure that a class with an abstract parent can be referenced."""
-        """
 
         class Sibling(Document):
             name = StringField()
@@ -1575,8 +1568,7 @@ class TestField(MongoDBTestCase):
             brother.save()
 
     def test_generic_reference(self):
-        """Ensure that a GenericReferenceField properly dereferences items.
+        """Ensure that a GenericReferenceField properly dereferences items."""
-        """
 
         class Link(Document):
             title = StringField()
@@ -1615,8 +1607,7 @@ class TestField(MongoDBTestCase):
         assert isinstance(bm.bookmark_object, Link)
 
     def test_generic_reference_list(self):
-        """Ensure that a ListField properly dereferences generic references.
+        """Ensure that a ListField properly dereferences generic references."""
-        """
 
         class Link(Document):
             title = StringField()
@@ -1719,8 +1710,7 @@ class TestField(MongoDBTestCase):
         assert bm.bookmark_object == post_1
 
     def test_generic_reference_string_choices(self):
-        """Ensure that a GenericReferenceField can handle choices as strings
+        """Ensure that a GenericReferenceField can handle choices as strings"""
-        """
 
         class Link(Document):
             title = StringField()
@@ -1812,8 +1802,7 @@ class TestField(MongoDBTestCase):
         assert user.bookmarks == [post_1]
 
     def test_generic_reference_list_item_modification(self):
-        """Ensure that modifications of related documents (through generic reference) don't influence on querying
+        """Ensure that modifications of related documents (through generic reference) don't influence on querying"""
-        """
 
         class Post(Document):
             title = StringField()
@@ -1901,8 +1890,7 @@ class TestField(MongoDBTestCase):
         assert doc == doc2
 
     def test_choices_allow_using_sets_as_choices(self):
-        """Ensure that sets can be used when setting choices
+        """Ensure that sets can be used when setting choices"""
-        """
 
         class Shirt(Document):
             size = StringField(choices={"M", "L"})
@@ -1921,8 +1909,7 @@ class TestField(MongoDBTestCase):
         shirt.validate()
 
     def test_choices_validation_accept_possible_value(self):
-        """Ensure that value is in a container of allowed values.
+        """Ensure that value is in a container of allowed values."""
-        """
 
         class Shirt(Document):
             size = StringField(choices=("S", "M"))
@@ -1931,8 +1918,7 @@ class TestField(MongoDBTestCase):
         shirt.validate()
 
     def test_choices_validation_reject_unknown_value(self):
-        """Ensure that unallowed value are rejected upon validation
+        """Ensure that unallowed value are rejected upon validation"""
-        """
 
         class Shirt(Document):
             size = StringField(choices=("S", "M"))
@@ -1990,8 +1976,7 @@ class TestField(MongoDBTestCase):
             shirt1.validate()
 
     def test_simple_choices_validation(self):
-        """Ensure that value is in a container of allowed values.
+        """Ensure that value is in a container of allowed values."""
-        """
 
         class Shirt(Document):
             size = StringField(max_length=3, choices=("S", "M", "L", "XL", "XXL"))
@@ -2040,12 +2025,11 @@ class TestField(MongoDBTestCase):
             shirt.validate()
 
     def test_simple_choices_validation_invalid_value(self):
-        """Ensure that error messages are correct.
+        """Ensure that error messages are correct."""
-        """
         SIZES = ("S", "M", "L", "XL", "XXL")
         COLORS = (("R", "Red"), ("B", "Blue"))
-        SIZE_MESSAGE = u"Value must be one of ('S', 'M', 'L', 'XL', 'XXL')"
+        SIZE_MESSAGE = "Value must be one of ('S', 'M', 'L', 'XL', 'XXL')"
-        COLOR_MESSAGE = u"Value must be one of ['R', 'B']"
+        COLOR_MESSAGE = "Value must be one of ['R', 'B']"
 
         class Shirt(Document):
             size = StringField(max_length=3, choices=SIZES)
@@ -2108,7 +2092,7 @@ class TestField(MongoDBTestCase):
             assert "comments" in error_dict
             assert 1 in error_dict["comments"]
             assert "content" in error_dict["comments"][1]
-            assert error_dict["comments"][1]["content"] == u"Field is required"
+            assert error_dict["comments"][1]["content"] == "Field is required"
 
         post.comments[1].content = "here we go"
         post.validate()
@@ -2120,7 +2104,7 @@ class TestField(MongoDBTestCase):
 
         class EnumField(BaseField):
             def __init__(self, **kwargs):
-                super(EnumField, self).__init__(**kwargs)
+                super().__init__(**kwargs)
 
             def to_mongo(self, value):
                 return value
@@ -2273,6 +2257,13 @@ class TestField(MongoDBTestCase):
         with pytest.raises(FieldDoesNotExist):
             Doc(bar="test")
 
+    def test_undefined_field_works_no_confusion_with_db_field(self):
+        class Doc(Document):
+            foo = StringField(db_field="bar")
+
+        with pytest.raises(FieldDoesNotExist):
+            Doc(bar="test")
+
 
 class TestEmbeddedDocumentListField(MongoDBTestCase):
     def setUp(self):
@@ -2615,11 +2606,11 @@ class TestEmbeddedDocumentListField(MongoDBTestCase):
         """
         post = self.BlogPost(
             comments=[
-                self.Comments(author="user1", message=u"сообщение"),
+                self.Comments(author="user1", message="сообщение"),
-                self.Comments(author="user2", message=u"хабарлама"),
+                self.Comments(author="user2", message="хабарлама"),
             ]
         ).save()
-        assert post.comments.get(message=u"сообщение").author == "user1"
+        assert post.comments.get(message="сообщение").author == "user1"
 
     def test_save(self):
         """

tests/fields/test_file_field.py

@@ -1,19 +1,17 @@
-# -*- coding: utf-8 -*-
 import copy
 import os
 import tempfile
 import unittest
+from io import BytesIO
 
 import gridfs
 import pytest
-import six
 
 from mongoengine import *
 from mongoengine.connection import get_db
-from mongoengine.python_support import StringIO
 
 try:
-    from PIL import Image
+    from PIL import Image  # noqa: F401
 
     HAS_PIL = True
 except ImportError:
@@ -30,7 +28,7 @@ TEST_IMAGE2_PATH = os.path.join(os.path.dirname(__file__), "mongodb_leaf.png")
 def get_file(path):
     """Use a BytesIO instead of a file to allow
     to have a one-liner and avoid that the file remains opened"""
-    bytes_io = StringIO()
+    bytes_io = BytesIO()
     with open(path, "rb") as f:
         bytes_io.write(f.read())
     bytes_io.seek(0)
@@ -50,15 +48,14 @@ class TestFileField(MongoDBTestCase):
         DemoFile.objects.create()
 
     def test_file_fields(self):
-        """Ensure that file fields can be written to and their data retrieved
+        """Ensure that file fields can be written to and their data retrieved"""
-        """
 
         class PutFile(Document):
             the_file = FileField()
 
         PutFile.drop_collection()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
         content_type = "text/plain"
 
         putfile = PutFile()
@@ -80,7 +77,7 @@ class TestFileField(MongoDBTestCase):
         PutFile.drop_collection()
 
         putfile = PutFile()
-        putstring = StringIO()
+        putstring = BytesIO()
         putstring.write(text)
         putstring.seek(0)
         putfile.the_file.put(putstring, content_type=content_type)
@@ -93,16 +90,15 @@ class TestFileField(MongoDBTestCase):
         result.the_file.delete()
 
     def test_file_fields_stream(self):
-        """Ensure that file fields can be written to and their data retrieved
+        """Ensure that file fields can be written to and their data retrieved"""
-        """
 
         class StreamFile(Document):
             the_file = FileField()
 
         StreamFile.drop_collection()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
-        more_text = six.b("Foo Bar")
+        more_text = b"Foo Bar"
         content_type = "text/plain"
 
         streamfile = StreamFile()
@@ -137,8 +133,8 @@ class TestFileField(MongoDBTestCase):
 
         StreamFile.drop_collection()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
-        more_text = six.b("Foo Bar")
+        more_text = b"Foo Bar"
 
         streamfile = StreamFile()
         streamfile.save()
@@ -167,8 +163,8 @@ class TestFileField(MongoDBTestCase):
         class SetFile(Document):
             the_file = FileField()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
-        more_text = six.b("Foo Bar")
+        more_text = b"Foo Bar"
 
         SetFile.drop_collection()
 
@@ -196,7 +192,7 @@ class TestFileField(MongoDBTestCase):
         GridDocument.drop_collection()
 
         with tempfile.TemporaryFile() as f:
-            f.write(six.b("Hello World!"))
+            f.write(b"Hello World!")
             f.flush()
 
             # Test without default
@@ -213,7 +209,7 @@ class TestFileField(MongoDBTestCase):
             assert doc_b.the_file.grid_id == doc_c.the_file.grid_id
 
             # Test with default
-            doc_d = GridDocument(the_file=six.b(""))
+            doc_d = GridDocument(the_file=b"")
             doc_d.save()
 
             doc_e = GridDocument.objects.with_id(doc_d.id)
@@ -230,8 +226,7 @@ class TestFileField(MongoDBTestCase):
         assert ["doc_b", "doc_e"] == grid_fs.list()
 
     def test_file_uniqueness(self):
-        """Ensure that each instance of a FileField is unique
+        """Ensure that each instance of a FileField is unique"""
-        """
 
         class TestFile(Document):
             name = StringField()
@@ -240,7 +235,7 @@ class TestFileField(MongoDBTestCase):
         # First instance
         test_file = TestFile()
         test_file.name = "Hello, World!"
-        test_file.the_file.put(six.b("Hello, World!"))
+        test_file.the_file.put(b"Hello, World!")
         test_file.save()
 
         # Second instance
@@ -287,8 +282,7 @@ class TestFileField(MongoDBTestCase):
         assert test_file.the_file.get().length == 4971
 
     def test_file_boolean(self):
-        """Ensure that a boolean test of a FileField indicates its presence
+        """Ensure that a boolean test of a FileField indicates its presence"""
-        """
 
         class TestFile(Document):
             the_file = FileField()
@@ -297,7 +291,7 @@ class TestFileField(MongoDBTestCase):
 
         test_file = TestFile()
         assert not bool(test_file.the_file)
-        test_file.the_file.put(six.b("Hello, World!"), content_type="text/plain")
+        test_file.the_file.put(b"Hello, World!", content_type="text/plain")
         test_file.save()
         assert bool(test_file.the_file)
 
@@ -319,7 +313,7 @@ class TestFileField(MongoDBTestCase):
         class TestFile(Document):
             the_file = FileField()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
         content_type = "text/plain"
 
         testfile = TestFile()
@@ -363,7 +357,7 @@ class TestFileField(MongoDBTestCase):
         testfile.the_file.put(text, content_type=content_type, filename="hello")
         testfile.save()
 
-        text = six.b("Bonjour, World!")
+        text = b"Bonjour, World!"
         testfile.the_file.replace(text, content_type=content_type, filename="hello")
         testfile.save()
 
@@ -387,7 +381,7 @@ class TestFileField(MongoDBTestCase):
         TestImage.drop_collection()
 
         with tempfile.TemporaryFile() as f:
-            f.write(six.b("Hello World!"))
+            f.write(b"Hello World!")
             f.flush()
 
             t = TestImage()
@@ -429,7 +423,7 @@ class TestFileField(MongoDBTestCase):
     @require_pil
     def test_image_field_resize(self):
         class TestImage(Document):
-            image = ImageField(size=(185, 37))
+            image = ImageField(size=(185, 37, True))
 
         TestImage.drop_collection()
 
@@ -471,7 +465,7 @@ class TestFileField(MongoDBTestCase):
     @require_pil
     def test_image_field_thumbnail(self):
         class TestImage(Document):
-            image = ImageField(thumbnail_size=(92, 18))
+            image = ImageField(thumbnail_size=(92, 18, True))
 
         TestImage.drop_collection()
 
@@ -503,21 +497,21 @@ class TestFileField(MongoDBTestCase):
         # First instance
         test_file = TestFile()
         test_file.name = "Hello, World!"
-        test_file.the_file.put(six.b("Hello, World!"), name="hello.txt")
+        test_file.the_file.put(b"Hello, World!", name="hello.txt")
         test_file.save()
 
         data = get_db("test_files").macumba.files.find_one()
         assert data.get("name") == "hello.txt"
 
         test_file = TestFile.objects.first()
-        assert test_file.the_file.read() == six.b("Hello, World!")
+        assert test_file.the_file.read() == b"Hello, World!"
 
         test_file = TestFile.objects.first()
-        test_file.the_file = six.b("HELLO, WORLD!")
+        test_file.the_file = b"Hello, World!"
         test_file.save()
 
         test_file = TestFile.objects.first()
-        assert test_file.the_file.read() == six.b("HELLO, WORLD!")
+        assert test_file.the_file.read() == b"Hello, World!"
 
     def test_copyable(self):
         class PutFile(Document):
@@ -525,7 +519,7 @@ class TestFileField(MongoDBTestCase):
 
         PutFile.drop_collection()
 
-        text = six.b("Hello, World!")
+        text = b"Hello, World!"
         content_type = "text/plain"
 
         putfile = PutFile()

tests/fields/test_float_field.py

@@ -1,6 +1,4 @@
-# -*- coding: utf-8 -*-
 import pytest
-import six
 
 from mongoengine import *
 
@@ -21,8 +19,7 @@ class TestFloatField(MongoDBTestCase):
         assert 1 == TestDocument.objects(float_fld__ne=1).count()
 
     def test_validation(self):
-        """Ensure that invalid values cannot be assigned to float fields.
+        """Ensure that invalid values cannot be assigned to float fields."""
-        """
 
         class Person(Document):
             height = FloatField(min_value=0.1, max_value=3.5)
@@ -52,9 +49,8 @@ class TestFloatField(MongoDBTestCase):
 
         big_person = BigPerson()
 
-        for value, value_type in enumerate(six.integer_types):
+        big_person.height = int(0)
-            big_person.height = value_type(value)
+        big_person.validate()
-            big_person.validate()
 
         big_person.height = 2 ** 500
         big_person.validate()

tests/fields/test_geo_fields.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import unittest
 
 from mongoengine import *
@@ -9,7 +8,7 @@ class TestGeoField(MongoDBTestCase):
     def _test_for_expected_error(self, Cls, loc, expected):
         try:
             Cls(loc=loc).validate()
-            self.fail("Should not validate the location {0}".format(loc))
+            self.fail(f"Should not validate the location {loc}")
         except ValidationError as e:
             assert expected == e.to_dict()["loc"]
 
@@ -291,8 +290,7 @@ class TestGeoField(MongoDBTestCase):
         Location(loc=[[[[1, 2], [3, 4], [5, 6], [1, 2]]]]).validate()
 
     def test_indexes_geopoint(self):
-        """Ensure that indexes are created automatically for GeoPointFields.
+        """Ensure that indexes are created automatically for GeoPointFields."""
-        """
 
         class Event(Document):
             title = StringField()
@@ -318,8 +316,7 @@ class TestGeoField(MongoDBTestCase):
         assert geo_indicies == [{"fields": [("venue.location", "2d")]}]
 
     def test_indexes_2dsphere(self):
-        """Ensure that indexes are created automatically for GeoPointFields.
+        """Ensure that indexes are created automatically for GeoPointFields."""
-        """
 
         class Event(Document):
             title = StringField()
@@ -333,8 +330,7 @@ class TestGeoField(MongoDBTestCase):
         assert {"fields": [("point", "2dsphere")]} in geo_indicies
 
     def test_indexes_2dsphere_embedded(self):
-        """Ensure that indexes are created automatically for GeoPointFields.
+        """Ensure that indexes are created automatically for GeoPointFields."""
-        """
 
         class Venue(EmbeddedDocument):
             name = StringField()
@@ -381,7 +377,7 @@ class TestGeoField(MongoDBTestCase):
 
             meta = {"indexes": [[("location", "2dsphere"), ("datetime", 1)]]}
 
-        assert [] == Log._geo_indices()
+        assert Log._geo_indices() == []
 
         Log.drop_collection()
         Log.ensure_indexes()
@@ -401,7 +397,7 @@ class TestGeoField(MongoDBTestCase):
                 "indexes": [{"fields": [("location", "2dsphere"), ("datetime", 1)]}]
             }
 
-        assert [] == Log._geo_indices()
+        assert Log._geo_indices() == []
 
         Log.drop_collection()
         Log.ensure_indexes()

tests/fields/test_int_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from mongoengine import *
@@ -8,8 +7,7 @@ from tests.utils import MongoDBTestCase
 
 class TestIntField(MongoDBTestCase):
     def test_int_validation(self):
-        """Ensure that invalid values cannot be assigned to int fields.
+        """Ensure that invalid values cannot be assigned to int fields."""
-        """
 
         class Person(Document):
             age = IntField(min_value=0, max_value=110)

tests/fields/test_lazy_reference_field.py

@@ -1,9 +1,9 @@
-# -*- coding: utf-8 -*-
 from bson import DBRef, ObjectId
 import pytest
 
 from mongoengine import *
 from mongoengine.base import LazyReference
+from mongoengine.context_managers import query_counter
 
 from tests.utils import MongoDBTestCase
 
@@ -152,7 +152,7 @@ class TestLazyReferenceField(MongoDBTestCase):
             LazyReference(BadDoc, animal.pk),
         ):
             with pytest.raises(ValidationError):
-                p = Ocurrence(person="test", animal=bad).save()
+                Ocurrence(person="test", animal=bad).save()
 
     def test_lazy_reference_query_conversion(self):
         """Ensure that LazyReferenceFields can be queried using objects and values
@@ -331,6 +331,50 @@ class TestLazyReferenceField(MongoDBTestCase):
         occ.in_embedded.in_list = [animal1.id, animal2.id]
         check_fields_type(occ)
 
+    def test_lazy_reference_embedded_dereferencing(self):
+        # Test case for #2375
+
+        # -- Test documents
+
+        class Author(Document):
+            name = StringField()
+
+        class AuthorReference(EmbeddedDocument):
+            author = LazyReferenceField(Author)
+
+        class Book(Document):
+            authors = EmbeddedDocumentListField(AuthorReference)
+
+        # -- Cleanup
+
+        Author.drop_collection()
+        Book.drop_collection()
+
+        # -- Create test data
+
+        author_1 = Author(name="A1").save()
+        author_2 = Author(name="A2").save()
+        author_3 = Author(name="A3").save()
+        book = Book(
+            authors=[
+                AuthorReference(author=author_1),
+                AuthorReference(author=author_2),
+                AuthorReference(author=author_3),
+            ]
+        ).save()
+
+        with query_counter() as qc:
+            book = Book.objects.first()
+            # Accessing the list must not trigger dereferencing.
+            book.authors
+            assert qc == 1
+
+        for ref in book.authors:
+            with pytest.raises(AttributeError):
+                ref["author"].name
+            assert isinstance(ref.author, LazyReference)
+            assert isinstance(ref.author.id, ObjectId)
+
 
 class TestGenericLazyReferenceField(MongoDBTestCase):
     def test_generic_lazy_reference_simple(self):
@@ -386,7 +430,7 @@ class TestGenericLazyReferenceField(MongoDBTestCase):
         mineral = Mineral(name="Granite").save()
 
         occ_animal = Ocurrence(living_thing=animal, thing=animal).save()
-        occ_vegetal = Ocurrence(living_thing=vegetal, thing=vegetal).save()
+        _ = Ocurrence(living_thing=vegetal, thing=vegetal).save()
         with pytest.raises(ValidationError):
             Ocurrence(living_thing=mineral).save()
 
@@ -458,7 +502,7 @@ class TestGenericLazyReferenceField(MongoDBTestCase):
         baddoc = BadDoc().save()
         for bad in (42, "foo", baddoc, LazyReference(BadDoc, animal.pk)):
             with pytest.raises(ValidationError):
-                p = Ocurrence(person="test", animal=bad).save()
+                Ocurrence(person="test", animal=bad).save()
 
     def test_generic_lazy_reference_query_conversion(self):
         class Member(Document):

tests/fields/test_long_field.py

@@ -1,11 +1,5 @@
-# -*- coding: utf-8 -*-
+from bson.int64 import Int64
 import pytest
-import six
-
-try:
-    from bson.int64 import Int64
-except ImportError:
-    Int64 = long
 
 from mongoengine import *
 from mongoengine.connection import get_db
@@ -28,11 +22,10 @@ class TestLongField(MongoDBTestCase):
         assert isinstance(
             db.test_long_field_considered_as_int64.find()[0]["some_long"], Int64
         )
-        assert isinstance(doc.some_long, six.integer_types)
+        assert isinstance(doc.some_long, int)
 
     def test_long_validation(self):
-        """Ensure that invalid values cannot be assigned to long fields.
+        """Ensure that invalid values cannot be assigned to long fields."""
-        """
 
         class TestDocument(Document):
             value = LongField(min_value=0, max_value=110)

tests/fields/test_map_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import datetime
 
 import pytest
@@ -136,11 +135,11 @@ class TestMapField(MongoDBTestCase):
 
         BlogPost.drop_collection()
 
-        tree = BlogPost(info_dict={u"éééé": {"description": u"VALUE: éééé"}})
+        tree = BlogPost(info_dict={"éééé": {"description": "VALUE: éééé"}})
 
         tree.save()
 
         assert (
-            BlogPost.objects.get(id=tree.id).info_dict[u"éééé"].description
+            BlogPost.objects.get(id=tree.id).info_dict["éééé"].description
-            == u"VALUE: éééé"
+            == "VALUE: éééé"
         )

tests/fields/test_reference_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from bson import DBRef, SON
 import pytest
 
@@ -88,7 +87,7 @@ class TestReferenceField(MongoDBTestCase):
             parent = ReferenceField("self", dbref=False)
 
         p = Person(name="Steve", parent=DBRef("person", "abcdefghijklmnop"))
-        assert p.to_mongo() == SON([("name", u"Steve"), ("parent", "abcdefghijklmnop")])
+        assert p.to_mongo() == SON([("name", "Steve"), ("parent", "abcdefghijklmnop")])
 
     def test_objectid_reference_fields(self):
         class Person(Document):
@@ -108,8 +107,7 @@ class TestReferenceField(MongoDBTestCase):
         assert p.parent == p1
 
     def test_undefined_reference(self):
-        """Ensure that ReferenceFields may reference undefined Documents.
+        """Ensure that ReferenceFields may reference undefined Documents."""
-        """
 
         class Product(Document):
             name = StringField()

tests/fields/test_sequence_field.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from mongoengine import *
 
 from tests.utils import MongoDBTestCase
@@ -21,7 +19,7 @@ class TestSequenceField(MongoDBTestCase):
         assert c["next"] == 10
 
         ids = [i.id for i in Person.objects]
-        assert ids == range(1, 11)
+        assert ids == list(range(1, 11))
 
         c = self.db["mongoengine.counters"].find_one({"_id": "person.id"})
         assert c["next"] == 10
@@ -76,7 +74,7 @@ class TestSequenceField(MongoDBTestCase):
         assert c["next"] == 10
 
         ids = [i.id for i in Person.objects]
-        assert ids == range(1, 11)
+        assert ids == list(range(1, 11))
 
         c = self.db["mongoengine.counters"].find_one({"_id": "jelly.id"})
         assert c["next"] == 10
@@ -101,10 +99,10 @@ class TestSequenceField(MongoDBTestCase):
         assert c["next"] == 10
 
         ids = [i.id for i in Person.objects]
-        assert ids == range(1, 11)
+        assert ids == list(range(1, 11))
 
         counters = [i.counter for i in Person.objects]
-        assert counters == range(1, 11)
+        assert counters == list(range(1, 11))
 
         c = self.db["mongoengine.counters"].find_one({"_id": "person.id"})
         assert c["next"] == 10
@@ -166,10 +164,10 @@ class TestSequenceField(MongoDBTestCase):
         assert c["next"] == 10
 
         ids = [i.id for i in Person.objects]
-        assert ids == range(1, 11)
+        assert ids == list(range(1, 11))
 
-        id = [i.id for i in Animal.objects]
+        _id = [i.id for i in Animal.objects]
-        assert id == range(1, 11)
+        assert _id == list(range(1, 11))
 
         c = self.db["mongoengine.counters"].find_one({"_id": "person.id"})
         assert c["next"] == 10
@@ -193,7 +191,7 @@ class TestSequenceField(MongoDBTestCase):
         assert c["next"] == 10
 
         ids = [i.id for i in Person.objects]
-        assert ids == map(str, range(1, 11))
+        assert ids == [str(i) for i in range(1, 11)]
 
         c = self.db["mongoengine.counters"].find_one({"_id": "person.id"})
         assert c["next"] == 10
@@ -267,12 +265,12 @@ class TestSequenceField(MongoDBTestCase):
         foo = Foo(name="Foo")
         foo.save()
 
-        assert not (
+        assert "base.counter" not in self.db["mongoengine.counters"].find().distinct(
-            "base.counter" in self.db["mongoengine.counters"].find().distinct("_id")
+            "_id"
         )
-        assert ("foo.counter" and "bar.counter") in self.db[
+        existing_counters = self.db["mongoengine.counters"].find().distinct("_id")
-            "mongoengine.counters"
+        assert "foo.counter" in existing_counters
-        ].find().distinct("_id")
+        assert "bar.counter" in existing_counters
         assert foo.counter == bar.counter
         assert foo._fields["counter"].owner_document == Foo
         assert bar._fields["counter"].owner_document == Bar

tests/fields/test_url_field.py

@@ -1,8 +1,6 @@
-# -*- coding: utf-8 -*-
 import pytest
 
 from mongoengine import *
-
 from tests.utils import MongoDBTestCase
 
 
@@ -28,20 +26,19 @@ class TestURLField(MongoDBTestCase):
             url = URLField()
 
         link = Link()
-        link.url = u"http://привет.com"
+        link.url = "http://привет.com"
 
         # TODO fix URL validation - this *IS* a valid URL
         # For now we just want to make sure that the error message is correct
         with pytest.raises(ValidationError) as exc_info:
             link.validate()
         assert (
-            unicode(exc_info.value)
+            str(exc_info.value)
-            == u"ValidationError (Link:None) (Invalid URL: http://\u043f\u0440\u0438\u0432\u0435\u0442.com: ['url'])"
+            == "ValidationError (Link:None) (Invalid URL: http://\u043f\u0440\u0438\u0432\u0435\u0442.com: ['url'])"
         )
 
     def test_url_scheme_validation(self):
-        """Ensure that URLFields validate urls with specific schemes properly.
+        """Ensure that URLFields validate urls with specific schemes properly."""
-        """
 
         class Link(Document):
             url = URLField()

tests/fields/test_uuid_field.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 import uuid
 
 import pytest
@@ -18,8 +17,7 @@ class TestUUIDField(MongoDBTestCase):
         assert get_as_pymongo(person) == {"_id": person.id, "api_key": str(uid)}
 
     def test_field_string(self):
-        """Test UUID fields storing as String
+        """Test UUID fields storing as String"""
-        """
         Person.drop_collection()
 
         uu = uuid.uuid4()

tests/fixtures.py

@@ -53,7 +53,7 @@ signals.post_save.connect(PickleSignalsTest.post_save, sender=PickleSignalsTest)
 signals.post_delete.connect(PickleSignalsTest.post_delete, sender=PickleSignalsTest)
 
 
-class Mixin(object):
+class Mixin:
     name = StringField()
 
 

tests/queryset/test_field_list.py

@@ -148,8 +148,7 @@ class TestOnlyExcludeAll(unittest.TestCase):
         assert qs._loaded_fields.as_dict() == {"c": {"$slice": 2}, "a": 1}
 
     def test_only(self):
-        """Ensure that QuerySet.only only returns the requested fields.
+        """Ensure that QuerySet.only only returns the requested fields."""
-        """
         person = self.Person(name="test", age=25)
         person.save()
 
@@ -365,8 +364,7 @@ class TestOnlyExcludeAll(unittest.TestCase):
         Email.drop_collection()
 
     def test_slicing_fields(self):
-        """Ensure that query slicing an array works.
+        """Ensure that query slicing an array works."""
-        """
 
         class Numbers(Document):
             n = ListField(IntField())
@@ -401,8 +399,7 @@ class TestOnlyExcludeAll(unittest.TestCase):
         assert numbers.n == [-5, -4, -3, -2, -1]
 
     def test_slicing_nested_fields(self):
-        """Ensure that query slicing an embedded array works.
+        """Ensure that query slicing an embedded array works."""
-        """
 
         class EmbeddedNumber(EmbeddedDocument):
             n = ListField(IntField())

tests/queryset/test_geo.py

@@ -496,8 +496,8 @@ class TestGeoQueries(MongoDBTestCase):
         p.save()
         qs = Place.objects().only("location")
         assert qs.as_pymongo()[0]["location"] == {
-            u"type": u"Point",
+            "type": "Point",
-            u"coordinates": [24.946861267089844, 60.16311983618494],
+            "coordinates": [24.946861267089844, 60.16311983618494],
         }
 
     def test_2dsphere_point_sets_correctly(self):

tests/queryset/test_pickable.py

@@ -1,8 +1,6 @@
 import pickle
-import unittest
 
 from mongoengine import Document, IntField, StringField
-from mongoengine.connection import connect
 from tests.utils import MongoDBTestCase
 
 
@@ -18,18 +16,15 @@ class TestQuerysetPickable(MongoDBTestCase):
     """
 
     def setUp(self):
-        super(TestQuerysetPickable, self).setUp()
+        super().setUp()
         self.john = Person.objects.create(name="John", age=21)
 
     def test_picke_simple_qs(self):
-
         qs = Person.objects.all()
-
         pickle.dumps(qs)
 
     def _get_loaded(self, qs):
         s = pickle.dumps(qs)
-
         return pickle.loads(s)
 
     def test_unpickle(self):

tests/queryset/test_queryset_aggregation.py

@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 import unittest
 import warnings
 
@@ -66,7 +64,7 @@ class TestQuerysetAggregate(MongoDBTestCase):
 
         pipeline = [{"$match": {"name": "Isabella Luanna"}}]
         data = Person.objects().aggregate(pipeline)
-        assert list(data) == [{u"_id": p1.pk, u"age": 16, u"name": u"Isabella Luanna"}]
+        assert list(data) == [{"_id": p1.pk, "age": 16, "name": "Isabella Luanna"}]
 
     def test_queryset_aggregation_with_skip(self):
         class Person(Document):

tests/queryset/test_transform.py

@@ -12,8 +12,7 @@ class TestTransform(unittest.TestCase):
         connect(db="mongoenginetest")
 
     def test_transform_query(self):
-        """Ensure that the _transform_query function operates correctly.
+        """Ensure that the _transform_query function operates correctly."""
-        """
         assert transform.query(name="test", age=30) == {"name": "test", "age": 30}
         assert transform.query(age__lt=30) == {"age": {"$lt": 30}}
         assert transform.query(age__gt=20, age__lt=50) == {
@@ -24,6 +23,12 @@ class TestTransform(unittest.TestCase):
         }
         assert transform.query(friend__age__gte=30) == {"friend.age": {"$gte": 30}}
         assert transform.query(name__exists=True) == {"name": {"$exists": True}}
+        assert transform.query(name=["Mark"], __raw__={"name": {"$in": "Tom"}}) == {
+            "$and": [{"name": ["Mark"]}, {"name": {"$in": "Tom"}}]
+        }
+        assert transform.query(name__in=["Tom"], __raw__={"name": "Mark"}) == {
+            "$and": [{"name": {"$in": ["Tom"]}}, {"name": "Mark"}]
+        }
 
     def test_transform_update(self):
         class LisDoc(Document):
@@ -82,8 +87,7 @@ class TestTransform(unittest.TestCase):
         assert update == {"$set": {"tags": ["mongo", "db"]}}
 
     def test_query_field_name(self):
-        """Ensure that the correct field name is used when querying.
+        """Ensure that the correct field name is used when querying."""
-        """
 
         class Comment(EmbeddedDocument):
             content = StringField(db_field="commentContent")
@@ -100,18 +104,17 @@ class TestTransform(unittest.TestCase):
         post = BlogPost(**data)
         post.save()
 
-        assert "postTitle" in BlogPost.objects(title=data["title"])._query
+        qs = BlogPost.objects(title=data["title"])
-        assert not ("title" in BlogPost.objects(title=data["title"])._query)
+        assert qs._query == {"postTitle": data["title"]}
-        assert BlogPost.objects(title=data["title"]).count() == 1
+        assert qs.count() == 1
 
-        assert "_id" in BlogPost.objects(pk=post.id)._query
+        qs = BlogPost.objects(pk=post.id)
-        assert BlogPost.objects(pk=post.id).count() == 1
+        assert qs._query == {"_id": post.id}
+        assert qs.count() == 1
 
-        assert (
+        qs = BlogPost.objects(comments__content="test")
-            "postComments.commentContent"
+        assert qs._query == {"postComments.commentContent": "test"}
-            in BlogPost.objects(comments__content="test")._query
+        assert qs.count() == 1
-        )
-        assert BlogPost.objects(comments__content="test").count() == 1
 
         BlogPost.drop_collection()
 
@@ -324,7 +327,7 @@ class TestTransform(unittest.TestCase):
         word = Word(word="abc", index=1)
         update = transform.update(MainDoc, pull__content__text=word)
         assert update == {
-            "$pull": {"content.text": SON([("word", u"abc"), ("index", 1)])}
+            "$pull": {"content.text": SON([("word", "abc"), ("index", 1)])}
         }
 
         update = transform.update(MainDoc, pull__content__heading="xyz")
@@ -338,6 +341,31 @@ class TestTransform(unittest.TestCase):
         )
         assert update == {"$pull": {"content.text": {"word": {"$nin": ["foo", "bar"]}}}}
 
+    def test_transform_embedded_document_list_fields(self):
+        """
+        Test added to check filtering
+        EmbeddedDocumentListField which is inside a EmbeddedDocumentField
+        """
+
+        class Drink(EmbeddedDocument):
+            id = StringField()
+            meta = {"strict": False}
+
+        class Shop(Document):
+            drinks = EmbeddedDocumentListField(Drink)
+
+        Shop.drop_collection()
+        drinks = [Drink(id="drink_1"), Drink(id="drink_2")]
+        Shop.objects.create(drinks=drinks)
+        q_obj = transform.query(
+            Shop, drinks__all=[{"$elemMatch": {"_id": x.id}} for x in drinks]
+        )
+        assert q_obj == {
+            "drinks": {"$all": [{"$elemMatch": {"_id": x.id}} for x in drinks]}
+        }
+
+        Shop.drop_collection()
+
 
 if __name__ == "__main__":
     unittest.main()

tests/queryset/test_visitor.py

@@ -23,8 +23,7 @@ class TestQ(unittest.TestCase):
         self.Person = Person
 
     def test_empty_q(self):
-        """Ensure that empty Q objects won't hurt.
+        """Ensure that empty Q objects won't hurt."""
-        """
         q1 = Q()
         q2 = Q(age__gte=18)
         q3 = Q()
@@ -58,8 +57,7 @@ class TestQ(unittest.TestCase):
         assert Post.objects.filter(Q(created_user=user)).count() == 1
 
     def test_and_combination(self):
-        """Ensure that Q-objects correctly AND together.
+        """Ensure that Q-objects correctly AND together."""
-        """
 
         class TestDoc(Document):
             x = IntField()
@@ -89,8 +87,7 @@ class TestQ(unittest.TestCase):
         assert query.to_query(TestDoc) == mongo_query
 
     def test_or_combination(self):
-        """Ensure that Q-objects correctly OR together.
+        """Ensure that Q-objects correctly OR together."""
-        """
 
         class TestDoc(Document):
             x = IntField()
@@ -101,8 +98,7 @@ class TestQ(unittest.TestCase):
         assert query == {"$or": [{"x": {"$lt": 3}}, {"x": {"$gt": 7}}]}
 
     def test_and_or_combination(self):
-        """Ensure that Q-objects handle ANDing ORed components.
+        """Ensure that Q-objects handle ANDing ORed components."""
-        """
 
         class TestDoc(Document):
             x = IntField()
@@ -136,8 +132,7 @@ class TestQ(unittest.TestCase):
         assert 2 == TestDoc.objects(q1 & q2).count()
 
     def test_or_and_or_combination(self):
-        """Ensure that Q-objects handle ORing ANDed ORed components. :)
+        """Ensure that Q-objects handle ORing ANDed ORed components. :)"""
-        """
 
         class TestDoc(Document):
             x = IntField()
@@ -208,8 +203,7 @@ class TestQ(unittest.TestCase):
         assert test.count() == 3
 
     def test_q(self):
-        """Ensure that Q objects may be used to query for documents.
+        """Ensure that Q objects may be used to query for documents."""
-        """
 
         class BlogPost(Document):
             title = StringField()
@@ -286,8 +280,7 @@ class TestQ(unittest.TestCase):
             self.Person.objects.filter("user1")
 
     def test_q_regex(self):
-        """Ensure that Q objects can be queried using regexes.
+        """Ensure that Q objects can be queried using regexes."""
-        """
         person = self.Person(name="Guido van Rossum")
         person.save()
 
@@ -320,8 +313,7 @@ class TestQ(unittest.TestCase):
         )
 
     def test_q_lists(self):
-        """Ensure that Q objects query ListFields correctly.
+        """Ensure that Q objects query ListFields correctly."""
-        """
 
         class BlogPost(Document):
             tags = ListField(StringField())

tests/test_common.py

@@ -1,5 +1,3 @@
-import unittest
-
 import pytest
 
 from mongoengine import Document

tests/test_connection.py

@@ -1,17 +1,12 @@
 import datetime
+import unittest
 
 from bson.tz_util import utc
 import pymongo
-
 from pymongo import MongoClient, ReadPreference
 from pymongo.errors import InvalidName, OperationFailure
 import pytest
 
-try:
-    import unittest2 as unittest
-except ImportError:
-    import unittest
-
 import mongoengine.connection
 from mongoengine import (
     DateTimeField,
@@ -34,18 +29,6 @@ def get_tz_awareness(connection):
     return connection.codec_options.tz_aware
 
 
-try:
-    import mongomock
-
-    MONGOMOCK_INSTALLED = True
-except ImportError:
-    MONGOMOCK_INSTALLED = False
-
-require_mongomock = pytest.mark.skipif(
-    not MONGOMOCK_INSTALLED, reason="you need mongomock installed to run this testcase"
-)
-
-
 class ConnectionTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
@@ -194,14 +177,12 @@ class ConnectionTest(unittest.TestCase):
         assert len(mongoengine.connection._connections) == 3
 
     def test_connect_with_invalid_db_name(self):
-        """Ensure that connect() method fails fast if db name is invalid
+        """Ensure that connect() method fails fast if db name is invalid"""
-        """
         with pytest.raises(InvalidName):
-            connect("mongomock://localhost")
+            connect("mongodb://localhost")
 
     def test_connect_with_db_name_external(self):
-        """Ensure that connect() works if db name is $external
+        """Ensure that connect() works if db name is $external"""
-        """
         """Ensure that the connect() method works properly."""
         connect("$external")
 
@@ -217,112 +198,11 @@ class ConnectionTest(unittest.TestCase):
         assert isinstance(conn, pymongo.mongo_client.MongoClient)
 
     def test_connect_with_invalid_db_name_type(self):
-        """Ensure that connect() method fails fast if db name has invalid type
+        """Ensure that connect() method fails fast if db name has invalid type"""
-        """
         with pytest.raises(TypeError):
             non_string_db_name = ["e. g. list instead of a string"]
             connect(non_string_db_name)
 
-    @require_mongomock
-    def test_connect_in_mocking(self):
-        """Ensure that the connect() method works properly in mocking.
-        """
-        connect("mongoenginetest", host="mongomock://localhost")
-        conn = get_connection()
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect("mongoenginetest2", host="mongomock://localhost", alias="testdb2")
-        conn = get_connection("testdb2")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            "mongoenginetest3",
-            host="mongodb://localhost",
-            is_mock=True,
-            alias="testdb3",
-        )
-        conn = get_connection("testdb3")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect("mongoenginetest4", is_mock=True, alias="testdb4")
-        conn = get_connection("testdb4")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            host="mongodb://localhost:27017/mongoenginetest5",
-            is_mock=True,
-            alias="testdb5",
-        )
-        conn = get_connection("testdb5")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(host="mongomock://localhost:27017/mongoenginetest6", alias="testdb6")
-        conn = get_connection("testdb6")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            host="mongomock://localhost:27017/mongoenginetest7",
-            is_mock=True,
-            alias="testdb7",
-        )
-        conn = get_connection("testdb7")
-        assert isinstance(conn, mongomock.MongoClient)
-
-    @require_mongomock
-    def test_default_database_with_mocking(self):
-        """Ensure that the default database is correctly set when using mongomock.
-        """
-        disconnect_all()
-
-        class SomeDocument(Document):
-            pass
-
-        conn = connect(host="mongomock://localhost:27017/mongoenginetest")
-        some_document = SomeDocument()
-        # database won't exist until we save a document
-        some_document.save()
-        assert conn.get_default_database().name == "mongoenginetest"
-        assert conn.database_names()[0] == "mongoenginetest"
-
-    @require_mongomock
-    def test_connect_with_host_list(self):
-        """Ensure that the connect() method works when host is a list
-
-        Uses mongomock to test w/o needing multiple mongod/mongos processes
-        """
-        connect(host=["mongomock://localhost"])
-        conn = get_connection()
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(host=["mongodb://localhost"], is_mock=True, alias="testdb2")
-        conn = get_connection("testdb2")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(host=["localhost"], is_mock=True, alias="testdb3")
-        conn = get_connection("testdb3")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            host=["mongomock://localhost:27017", "mongomock://localhost:27018"],
-            alias="testdb4",
-        )
-        conn = get_connection("testdb4")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            host=["mongodb://localhost:27017", "mongodb://localhost:27018"],
-            is_mock=True,
-            alias="testdb5",
-        )
-        conn = get_connection("testdb5")
-        assert isinstance(conn, mongomock.MongoClient)
-
-        connect(
-            host=["localhost:27017", "localhost:27018"], is_mock=True, alias="testdb6"
-        )
-        conn = get_connection("testdb6")
-        assert isinstance(conn, mongomock.MongoClient)
-
     def test_disconnect_cleans_globals(self):
         """Ensure that the disconnect() method cleans the globals objects"""
         connections = mongoengine.connection._connections
@@ -348,7 +228,7 @@ class ConnectionTest(unittest.TestCase):
 
     def test_disconnect_cleans_cached_collection_attribute_in_document(self):
         """Ensure that the disconnect() method works properly"""
-        conn1 = connect("mongoenginetest")
+        connect("mongoenginetest")
 
         class History(Document):
             pass
@@ -452,8 +332,7 @@ class ConnectionTest(unittest.TestCase):
         disconnect_all()
 
     def test_sharing_connections(self):
-        """Ensure that connections are shared when the connection settings are exactly the same
+        """Ensure that connections are shared when the connection settings are exactly the same"""
-        """
         connect("mongoenginetests", alias="testdb1")
         expected_connection = get_connection("testdb1")
 
@@ -518,7 +397,7 @@ class ConnectionTest(unittest.TestCase):
         """Ensure connect() uses the username & password params if the URI
         doesn't explicitly specify them.
         """
-        c = connect(
+        connect(
             host="mongodb://localhost/mongoenginetest", username="user", password="pass"
         )
 
@@ -564,8 +443,7 @@ class ConnectionTest(unittest.TestCase):
         authd_conn.admin.system.users.delete_many({})
 
     def test_register_connection(self):
-        """Ensure that connections with different aliases may be registered.
+        """Ensure that connections with different aliases may be registered."""
-        """
         register_connection("testdb", "mongoenginetest2")
 
         with pytest.raises(ConnectionFailure):
@@ -578,8 +456,7 @@ class ConnectionTest(unittest.TestCase):
         assert db.name == "mongoenginetest2"
 
     def test_register_connection_defaults(self):
-        """Ensure that defaults are used when the host and port are None.
+        """Ensure that defaults are used when the host and port are None."""
-        """
         register_connection("testdb", "mongoenginetest", host=None, port=None)
 
         conn = get_connection("testdb")
@@ -632,7 +509,7 @@ class ConnectionTest(unittest.TestCase):
         """Ensure connect() works when specifying a replicaSet via the
         MongoDB URI.
         """
-        c = connect(host="mongodb://localhost/test?replicaSet=local-rs")
+        connect(host="mongodb://localhost/test?replicaSet=local-rs")
         db = get_db()
         assert isinstance(db, pymongo.database.Database)
         assert db.name == "test"

tests/test_connection_mongomock.py

@@ -0,0 +1,173 @@
+import unittest
+
+import pytest
+
+import mongoengine.connection
+from mongoengine import (
+    Document,
+    StringField,
+    connect,
+    disconnect_all,
+)
+from mongoengine.connection import get_connection
+
+
+try:
+    import mongomock
+
+    MONGOMOCK_INSTALLED = True
+except ImportError:
+    MONGOMOCK_INSTALLED = False
+
+require_mongomock = pytest.mark.skipif(
+    not MONGOMOCK_INSTALLED, reason="you need mongomock installed to run this testcase"
+)
+
+
+class MongoMockConnectionTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        disconnect_all()
+
+    @classmethod
+    def tearDownClass(cls):
+        disconnect_all()
+
+    def tearDown(self):
+        mongoengine.connection._connection_settings = {}
+        mongoengine.connection._connections = {}
+        mongoengine.connection._dbs = {}
+
+    @require_mongomock
+    def test_connect_in_mocking(self):
+        """Ensure that the connect() method works properly in mocking."""
+        connect("mongoenginetest", host="mongomock://localhost")
+        conn = get_connection()
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect("mongoenginetest2", host="mongomock://localhost", alias="testdb2")
+        conn = get_connection("testdb2")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            "mongoenginetest3",
+            host="mongodb://localhost",
+            is_mock=True,
+            alias="testdb3",
+        )
+        conn = get_connection("testdb3")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect("mongoenginetest4", is_mock=True, alias="testdb4")
+        conn = get_connection("testdb4")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            host="mongodb://localhost:27017/mongoenginetest5",
+            is_mock=True,
+            alias="testdb5",
+        )
+        conn = get_connection("testdb5")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(host="mongomock://localhost:27017/mongoenginetest6", alias="testdb6")
+        conn = get_connection("testdb6")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            host="mongomock://localhost:27017/mongoenginetest7",
+            is_mock=True,
+            alias="testdb7",
+        )
+        conn = get_connection("testdb7")
+        assert isinstance(conn, mongomock.MongoClient)
+
+    @require_mongomock
+    def test_default_database_with_mocking(self):
+        """Ensure that the default database is correctly set when using mongomock."""
+        disconnect_all()
+
+        class SomeDocument(Document):
+            pass
+
+        conn = connect(host="mongomock://localhost:27017/mongoenginetest")
+        some_document = SomeDocument()
+        # database won't exist until we save a document
+        some_document.save()
+        assert SomeDocument.objects.count() == 1
+        assert conn.get_default_database().name == "mongoenginetest"
+        assert conn.list_database_names()[0] == "mongoenginetest"
+
+    @require_mongomock
+    def test_basic_queries_against_mongomock(self):
+        disconnect_all()
+
+        connect(host="mongomock://localhost:27017/mongoenginetest")
+
+        class Person(Document):
+            name = StringField()
+
+        Person.drop_collection()
+        assert Person.objects.count() == 0
+
+        bob = Person(name="Bob").save()
+        john = Person(name="John").save()
+        assert Person.objects.count() == 2
+
+        qs = Person.objects(name="Bob")
+        assert qs.count() == 1
+        assert qs.first() == bob
+        assert list(qs.as_pymongo()) == [{"_id": bob.id, "name": "Bob"}]
+
+        pipeline = [{"$project": {"name": {"$toUpper": "$name"}}}]
+        data = Person.objects.order_by("name").aggregate(pipeline)
+        assert list(data) == [
+            {"_id": bob.id, "name": "BOB"},
+            {"_id": john.id, "name": "JOHN"},
+        ]
+
+        Person.drop_collection()
+        assert Person.objects.count() == 0
+
+    @require_mongomock
+    def test_connect_with_host_list(self):
+        """Ensure that the connect() method works when host is a list
+
+        Uses mongomock to test w/o needing multiple mongod/mongos processes
+        """
+        connect(host=["mongomock://localhost"])
+        conn = get_connection()
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(host=["mongodb://localhost"], is_mock=True, alias="testdb2")
+        conn = get_connection("testdb2")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(host=["localhost"], is_mock=True, alias="testdb3")
+        conn = get_connection("testdb3")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            host=["mongomock://localhost:27017", "mongomock://localhost:27018"],
+            alias="testdb4",
+        )
+        conn = get_connection("testdb4")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            host=["mongodb://localhost:27017", "mongodb://localhost:27018"],
+            is_mock=True,
+            alias="testdb5",
+        )
+        conn = get_connection("testdb5")
+        assert isinstance(conn, mongomock.MongoClient)
+
+        connect(
+            host=["localhost:27017", "localhost:27018"], is_mock=True, alias="testdb6"
+        )
+        conn = get_connection("testdb6")
+        assert isinstance(conn, mongomock.MongoClient)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_context_managers.py

@@ -8,6 +8,8 @@ from mongoengine.context_managers import (
     no_dereference,
     no_sub_classes,
     query_counter,
+    set_read_write_concern,
+    set_write_concern,
     switch_collection,
     switch_db,
 )
@@ -15,6 +17,52 @@ from mongoengine.pymongo_support import count_documents
 
 
 class TestContextManagers:
+    def test_set_write_concern(self):
+        connect("mongoenginetest")
+
+        class User(Document):
+            name = StringField()
+
+        collection = User._get_collection()
+        original_write_concern = collection.write_concern
+
+        with set_write_concern(
+            collection, {"w": "majority", "j": True, "wtimeout": 1234}
+        ) as updated_collection:
+            assert updated_collection.write_concern.document == {
+                "w": "majority",
+                "j": True,
+                "wtimeout": 1234,
+            }
+
+        assert original_write_concern.document == collection.write_concern.document
+
+    def test_set_read_write_concern(self):
+        connect("mongoenginetest")
+
+        class User(Document):
+            name = StringField()
+
+        collection = User._get_collection()
+
+        original_read_concern = collection.read_concern
+        original_write_concern = collection.write_concern
+
+        with set_read_write_concern(
+            collection,
+            {"w": "majority", "j": True, "wtimeout": 1234},
+            {"level": "local"},
+        ) as update_collection:
+            assert update_collection.read_concern.document == {"level": "local"}
+            assert update_collection.write_concern.document == {
+                "w": "majority",
+                "j": True,
+                "wtimeout": 1234,
+            }
+
+        assert original_read_concern.document == collection.read_concern.document
+        assert original_write_concern.document == collection.write_concern.document
+
     def test_switch_db_context_manager(self):
         connect("mongoenginetest")
         register_connection("testdb-1", "mongoenginetest2")
@@ -69,8 +117,7 @@ class TestContextManagers:
         assert 1 == Group.objects.count()
 
     def test_no_dereference_context_manager_object_id(self):
-        """Ensure that DBRef items in ListFields aren't dereferenced.
+        """Ensure that DBRef items in ListFields aren't dereferenced."""
-        """
         connect("mongoenginetest")
 
         class User(Document):
@@ -107,8 +154,7 @@ class TestContextManagers:
         assert isinstance(group.generic, User)
 
     def test_no_dereference_context_manager_dbref(self):
-        """Ensure that DBRef items in ListFields aren't dereferenced.
+        """Ensure that DBRef items in ListFields aren't dereferenced."""
-        """
         connect("mongoenginetest")
 
         class User(Document):
@@ -134,11 +180,11 @@ class TestContextManagers:
 
         with no_dereference(Group) as Group:
             group = Group.objects.first()
-            assert all([not isinstance(m, User) for m in group.members])
+            assert all(not isinstance(m, User) for m in group.members)
             assert not isinstance(group.ref, User)
             assert not isinstance(group.generic, User)
 
-        assert all([isinstance(m, User) for m in group.members])
+        assert all(isinstance(m, User) for m in group.members)
         assert isinstance(group.ref, User)
         assert isinstance(group.generic, User)
 
@@ -216,7 +262,7 @@ class TestContextManagers:
 
     def test_query_counter_does_not_swallow_exception(self):
         with pytest.raises(TypeError):
-            with query_counter() as q:
+            with query_counter():
                 raise TypeError()
 
     def test_query_counter_temporarily_modifies_profiling_level(self):
@@ -226,12 +272,12 @@ class TestContextManagers:
         initial_profiling_level = db.profiling_level()
 
         try:
-            NEW_LEVEL = 1
+            new_level = 1
-            db.set_profiling_level(NEW_LEVEL)
+            db.set_profiling_level(new_level)
-            assert db.profiling_level() == NEW_LEVEL
+            assert db.profiling_level() == new_level
-            with query_counter() as q:
+            with query_counter():
                 assert db.profiling_level() == 2
-            assert db.profiling_level() == NEW_LEVEL
+            assert db.profiling_level() == new_level
         except Exception:
             db.set_profiling_level(
                 initial_profiling_level