feat: update code collection check

docs/tutorial.rst

@@ -206,10 +206,7 @@ object::
         ross.last_name = 'Lawley'
         ross.save()
 
-Assign another user to a variable called ``john``, just like we did above with
-``ross``.
-
-Now that we've got our users in the database, let's add a couple of posts::
+Now that we've got our user in the database, let's add a couple of posts::
 
     post1 = TextPost(title='Fun with MongoEngine', author=john)
     post1.content = 'Took a look at MongoEngine today, looks pretty cool.'

mongoengine/base/document.py

@@ -1,6 +1,6 @@
 import copy
 import numbers
-from collections import Hashable
+from collections.abc import Hashable
 from functools import partial
 
 from bson import ObjectId, json_util

mongoengine/document.py

@@ -167,63 +167,45 @@ class Document(BaseDocument):
 
     @classmethod
     def _get_collection(cls):
-        """Return a PyMongo collection for the document."""
+        """Returns the collection for the document."""
+        # TODO: use new get_collection() with PyMongo3 ?
         if not hasattr(cls, '_collection') or cls._collection is None:
-
-            # Get the collection, either capped or regular.
+            db = cls._get_db()
+            collection_name = cls._get_collection_name()
+            # Create collection as a capped collection if specified
             if cls._meta.get('max_size') or cls._meta.get('max_documents'):
-                cls._collection = cls._get_capped_collection()
-            else:
-                db = cls._get_db()
-                collection_name = cls._get_collection_name()
-                cls._collection = db[collection_name]
+                # Get max document limit and max byte size from meta
+                max_size = cls._meta.get('max_size') or 10 * 2 ** 20  # 10MB default
+                max_documents = cls._meta.get('max_documents')
+                # Round up to next 256 bytes as MongoDB would do it to avoid exception
+                if max_size % 256:
+                    max_size = (max_size // 256 + 1) * 256
 
-            # Ensure indexes on the collection unless auto_create_index was
-            # set to False.
+                if collection_name in db.collection_names():
+                    cls._collection = db[collection_name]
+                    # The collection already exists, check if its capped
+                    # options match the specified capped options
+                    options = cls._collection.options()
+                    if options.get('max') != max_documents or \
+                            options.get('size') != max_size:
+                        msg = (('Cannot create collection "%s" as a capped '
+                                'collection as it already exists')
+                               % cls._collection)
+                        raise InvalidCollectionError(msg)
+                else:
+                    # Create the collection as a capped collection
+                    opts = {'capped': True, 'size': max_size}
+                    if max_documents:
+                        opts['max'] = max_documents
+                    cls._collection = db.create_collection(
+                        collection_name, **opts
+                    )
+            else:
+                cls._collection = db[collection_name]
             if cls._meta.get('auto_create_index', True):
                 cls.ensure_indexes()
-
         return cls._collection
 
-    @classmethod
-    def _get_capped_collection(cls):
-        """Create a new or get an existing capped PyMongo collection."""
-        db = cls._get_db()
-        collection_name = cls._get_collection_name()
-
-        # Get max document limit and max byte size from meta.
-        max_size = cls._meta.get('max_size') or 10 * 2 ** 20  # 10MB default
-        max_documents = cls._meta.get('max_documents')
-
-        # MongoDB will automatically raise the size to make it a multiple of
-        # 256 bytes. We raise it here ourselves to be able to reliably compare
-        # the options below.
-        if max_size % 256:
-            max_size = (max_size // 256 + 1) * 256
-
-        # If the collection already exists and has different options
-        # (i.e. isn't capped or has different max/size), raise an error.
-        if collection_name in db.collection_names():
-            collection = db[collection_name]
-            options = collection.options()
-            if (
-                options.get('max') != max_documents or
-                options.get('size') != max_size
-            ):
-                raise InvalidCollectionError(
-                    'Cannot create collection "{}" as a capped '
-                    'collection as it already exists'.format(cls._collection)
-                )
-
-            return collection
-
-        # Create a new capped collection.
-        opts = {'capped': True, 'size': max_size}
-        if max_documents:
-            opts['max'] = max_documents
-
-        return db.create_collection(collection_name, **opts)
-
     def to_mongo(self, *args, **kwargs):
         data = super(Document, self).to_mongo(*args, **kwargs)
 
@@ -826,7 +808,7 @@ class Document(BaseDocument):
         collection = cls._get_collection()
         # 746: when connection is via mongos, the read preference is not necessarily an indication that
         # this code runs on a secondary
-        if not collection.is_mongos and collection.read_preference > 1:
+        if collection.is_mongos is not None and collection.read_preference.mode > 1:
             return
 
         # determine if an index which we are creating includes

mongoengine/fields.py

@@ -6,7 +6,7 @@ import socket
 import time
 import uuid
 import warnings
-from collections import Mapping
+from collections.abc import Mapping
 from operator import itemgetter
 
 from bson import Binary, DBRef, ObjectId, SON
@@ -608,9 +608,9 @@ class EmbeddedDocumentField(BaseField):
     """
 
     def __init__(self, document_type, **kwargs):
-        if not (
-            isinstance(document_type, six.string_types) or
-            issubclass(document_type, EmbeddedDocument)
+        if (
+            not isinstance(document_type, six.string_types) and
+            not issubclass(document_type, EmbeddedDocument)
         ):
             self.error('Invalid embedded document class provided to an '
                        'EmbeddedDocumentField')