Added EmbeddedDocumentListField Implementation

- Added new field type: EmbeddedDocumentListField.
- Provides additional query ability for lists of embedded documents.
- Closes MongoEngine/mongoengine#503.

mongoengine/base/datastructures.py

@@ -2,8 +2,9 @@ import weakref
 import functools
 import itertools
 from mongoengine.common import _import_class
+from mongoengine.errors import DoesNotExist, MultipleObjectsReturned
 
-__all__ = ("BaseDict", "BaseList")
+__all__ = ("BaseDict", "BaseList", "EmbeddedDocumentList")
 
 
 class BaseDict(dict):
@@ -106,7 +107,7 @@ class BaseList(list):
         if isinstance(instance, (Document, EmbeddedDocument)):
             self._instance = weakref.proxy(instance)
         self._name = name
-        return super(BaseList, self).__init__(list_items)
+        super(BaseList, self).__init__(list_items)
 
     def __getitem__(self, key, *args, **kwargs):
         value = super(BaseList, self).__getitem__(key)
@@ -191,6 +192,167 @@ class BaseList(list):
                 self._instance._mark_as_changed(self._name)
 
 
+class EmbeddedDocumentList(BaseList):
+
+    @classmethod
+    def __match_all(cls, i, kwargs):
+        items = kwargs.items()
+        return all([
+            getattr(i, k) == v or str(getattr(i, k)) == v for k, v in items
+        ])
+
+    @classmethod
+    def __only_matches(cls, obj, kwargs):
+        if not kwargs:
+            return obj
+        return filter(lambda i: cls.__match_all(i, kwargs), obj)
+
+    def __init__(self, list_items, instance, name):
+        super(EmbeddedDocumentList, self).__init__(list_items, instance, name)
+        self._instance = instance
+
+    def filter(self, **kwargs):
+        """
+        Filters the list by only including embedded documents with the
+        given keyword arguments.
+
+        :param kwargs: The keyword arguments corresponding to the fields to
+         filter on. *Multiple arguments are treated as if they are ANDed
+         together.*
+        :return: A new ``EmbeddedDocumentList`` containing the matching
+         embedded documents.
+
+        Raises ``AttributeError`` if a given keyword is not a valid field for
+        the embedded document class.
+        """
+        values = self.__only_matches(self, kwargs)
+        return EmbeddedDocumentList(values, self._instance, self._name)
+
+    def exclude(self, **kwargs):
+        """
+        Filters the list by excluding embedded documents with the given
+        keyword arguments.
+
+        :param kwargs: The keyword arguments corresponding to the fields to
+         exclude on. *Multiple arguments are treated as if they are ANDed
+         together.*
+        :return: A new ``EmbeddedDocumentList`` containing the non-matching
+         embedded documents.
+
+        Raises ``AttributeError`` if a given keyword is not a valid field for
+        the embedded document class.
+        """
+        exclude = self.__only_matches(self, kwargs)
+        values = [item for item in self if item not in exclude]
+        return EmbeddedDocumentList(values, self._instance, self._name)
+
+    def count(self):
+        """
+        The number of embedded documents in the list.
+
+        :return: The length of the list, equivalent to the result of ``len()``.
+        """
+        return len(self)
+
+    def get(self, **kwargs):
+        """
+        Retrieves an embedded document determined by the given keyword
+        arguments.
+
+        :param kwargs: The keyword arguments corresponding to the fields to
+         search on. *Multiple arguments are treated as if they are ANDed
+         together.*
+        :return: The embedded document matched by the given keyword arguments.
+
+        Raises ``DoesNotExist`` if the arguments used to query an embedded
+        document returns no results. ``MultipleObjectsReturned`` if more
+        than one result is returned.
+        """
+        values = self.__only_matches(self, kwargs)
+        if len(values) == 0:
+            raise DoesNotExist(
+                "%s matching query does not exist." % self._name
+            )
+        elif len(values) > 1:
+            raise MultipleObjectsReturned(
+                "%d items returned, instead of 1" % len(values)
+            )
+
+        return values[0]
+
+    def first(self):
+        """
+        Returns the first embedded document in the list, or ``None`` if empty.
+        """
+        if len(self) > 0:
+            return self[0]
+
+    def create(self, **values):
+        """
+        Creates a new embedded document and saves it to the database.
+
+        .. note::
+            The embedded document changes are not automatically saved
+            to the database after calling this method.
+
+        :param values: A dictionary of values for the embedded document.
+        :return: The new embedded document instance.
+        """
+        name = self._name
+        EmbeddedClass = self._instance._fields[name].field.document_type_obj
+        self._instance[self._name].append(EmbeddedClass(**values))
+
+        return self._instance[self._name][-1]
+
+    def save(self, *args, **kwargs):
+        """
+        Saves the ancestor document.
+
+        :param args: Arguments passed up to the ancestor Document's save
+         method.
+        :param kwargs: Keyword arguments passed up to the ancestor Document's
+         save method.
+        """
+        self._instance.save(*args, **kwargs)
+
+    def delete(self):
+        """
+        Deletes the embedded documents from the database.
+
+        .. note::
+            The embedded document changes are not automatically saved
+            to the database after calling this method.
+
+        :return: The number of entries deleted.
+        """
+        values = list(self)
+        for item in values:
+            self._instance[self._name].remove(item)
+
+        return len(values)
+
+    def update(self, **update):
+        """
+        Updates the embedded documents with the given update values.
+
+        .. note::
+            The embedded document changes are not automatically saved
+            to the database after calling this method.
+
+        :param update: A dictionary of update values to apply to each
+         embedded document.
+        :return: The number of entries updated.
+        """
+        if len(update) == 0:
+            return 0
+        values = list(self)
+        for item in values:
+            for k, v in update.items():
+                setattr(item, k, v)
+
+        return len(values)
+
+
 class StrictDict(object):
     __slots__ = ()
     _special_fields = set(['get', 'pop', 'iteritems', 'items', 'keys', 'create'])