Fixed inheritance collection issue

mongoengine/queryset.py

@@ -1146,9 +1146,8 @@ class QuerySetManager(object):
             return self
 
         db = _get_db()
-        if db not in self._collections:
+        collection = owner._meta['collection']
-            collection = owner._meta['collection']
+        if (db, collection) not in self._collections:
-
             # Create collection as a capped collection if specified
             if owner._meta['max_size'] or owner._meta['max_documents']:
                 # Get max document limit and max byte size from meta
@@ -1156,10 +1155,10 @@ class QuerySetManager(object):
                 max_documents = owner._meta['max_documents']
 
                 if collection in db.collection_names():
-                    self._collections[db] = db[collection]
+                    self._collections[(db, collection)] = db[collection]
                     # The collection already exists, check if its capped
                     # options match the specified capped options
-                    options = self._collections[db].options()
+                    options = self._collections[(db, collection)].options()
                     if options.get('max') != max_documents or \
                        options.get('size') != max_size:
                         msg = ('Cannot create collection "%s" as a capped '
@@ -1170,15 +1169,15 @@ class QuerySetManager(object):
                     opts = {'capped': True, 'size': max_size}
                     if max_documents:
                         opts['max'] = max_documents
-                    self._collections[db] = db.create_collection(
+                    self._collections[(db, collection)] = db.create_collection(
                         collection, **opts
                     )
             else:
-                self._collections[db] = db[collection]
+                self._collections[(db, collection)] = db[collection]
 
         # owner is the document that contains the QuerySetManager
         queryset_class = owner._meta['queryset_class'] or QuerySet
-        queryset = queryset_class(owner, self._collections[db])
+        queryset = queryset_class(owner, self._collections[(db, collection)])
         if self._manager_func:
             if self._manager_func.func_code.co_argcount == 1:
                 queryset = self._manager_func(queryset)

tests/document.py

@@ -200,6 +200,37 @@ class DocumentTest(unittest.TestCase):
         Person.drop_collection()
         self.assertFalse(collection in self.db.collection_names())
 
+    def test_inherited_collections(self):
+        """Ensure that subclassed documents don't override parents' collections.
+        """
+        class Drink(Document):
+            name = StringField()
+
+        class AlcoholicDrink(Drink):
+            meta = {'collection': 'booze'}
+
+        class Drinker(Document):
+            drink = GenericReferenceField()
+
+        Drink.drop_collection()
+        AlcoholicDrink.drop_collection()
+        Drinker.drop_collection()
+
+        red_bull = Drink(name='Red Bull')
+        red_bull.save()
+
+        programmer = Drinker(drink=red_bull)
+        programmer.save()
+
+        beer = AlcoholicDrink(name='Beer')
+        beer.save()
+
+        real_person = Drinker(drink=beer)
+        real_person.save()
+
+        self.assertEqual(Drinker.objects[0].drink.name, red_bull.name)
+        self.assertEqual(Drinker.objects[1].drink.name, beer.name)
+
     def test_capped_collection(self):
         """Ensure that capped collections work properly.
         """