Fix filtering by embedded_doc=None

mongoengine/fields.py

@@ -577,7 +577,7 @@ class EmbeddedDocumentField(BaseField):
         return self.document_type._fields.get(member_name)
 
     def prepare_query_value(self, op, value):
-        if not isinstance(value, self.document_type):
+        if value is not None and not isinstance(value, self.document_type):
             value = self.document_type._from_son(value)
         super(EmbeddedDocumentField, self).prepare_query_value(op, value)
         return self.to_mongo(value)

mongoengine/queryset/base.py

@@ -933,14 +933,6 @@ class BaseQuerySet(object):
         queryset._ordering = queryset._get_order_by(keys)
         return queryset
 
-    def comment(self, text):
-        """Add a comment to the query.
-
-        See https://docs.mongodb.com/manual/reference/method/cursor.comment/#cursor.comment
-        for details.
-        """
-        return self._chainable_method("comment", text)
-
     def explain(self, format=False):
         """Return an explain plan record for the
         :class:`~mongoengine.queryset.QuerySet`\ 's cursor.

tests/queryset/queryset.py

@@ -339,6 +339,7 @@ class QuerySetTest(unittest.TestCase):
 
     def test_update_write_concern(self):
         """Test that passing write_concern works"""
+
         self.Person.drop_collection()
 
         write_concern = {"fsync": True}
@@ -1238,7 +1239,8 @@ class QuerySetTest(unittest.TestCase):
             self.assertFalse('$orderby' in q.get_ops()[0]['query'])
 
     def test_find_embedded(self):
-        """Ensure that an embedded document is properly returned from a query.
+        """Ensure that an embedded document is properly returned from
+        a query.
         """
         class User(EmbeddedDocument):
             name = StringField()
@@ -1249,16 +1251,31 @@ class QuerySetTest(unittest.TestCase):
 
         BlogPost.drop_collection()
 
-        post = BlogPost(content='Had a good coffee today...')
-        post.author = User(name='Test User')
-        post.save()
+        BlogPost.objects.create(
+            author=User(name='Test User'),
+            content='Had a good coffee today...'
+        )
 
         result = BlogPost.objects.first()
         self.assertTrue(isinstance(result.author, User))
         self.assertEqual(result.author.name, 'Test User')
 
+    def test_find_empty_embedded(self):
+        """Ensure that you can save and find an empty embedded document."""
+        class User(EmbeddedDocument):
+            name = StringField()
+
+        class BlogPost(Document):
+            content = StringField()
+            author = EmbeddedDocumentField(User)
+
         BlogPost.drop_collection()
 
+        BlogPost.objects.create(content='Anonymous post...')
+
+        result = BlogPost.objects.get(author=None)
+        self.assertEqual(result.author, None)
+
     def test_find_dict_item(self):
         """Ensure that DictField items may be found.
         """
@@ -2198,21 +2215,6 @@ class QuerySetTest(unittest.TestCase):
             a.author.name for a in Author.objects.order_by('-author__age')]
         self.assertEqual(names, ['User A', 'User B', 'User C'])
 
-    def test_comment(self):
-        """Make sure adding a comment to the query works."""
-        class User(Document):
-            age = IntField()
-
-        with db_ops_tracker() as q:
-            adult = (User.objects.filter(age__gte=18)
-                .comment('looking for an adult')
-                .first())
-            ops = q.get_ops()
-            self.assertEqual(len(ops), 1)
-            op = ops[0]
-            self.assertEqual(op['query']['$query'], {'age': {'$gte': 18}})
-            self.assertEqual(op['query']['$comment'], 'looking for an adult')
-
     def test_map_reduce(self):
         """Ensure map/reduce is both mapping and reducing.
         """