Handle DBRefs correctly within Q objects. Closes #55

mongoengine/queryset.py

@@ -133,6 +133,17 @@ class Q(object):
         if isinstance(value, pymongo.objectid.ObjectId):
             value = unicode(value)
 
+        # Handle DBRef
+        if isinstance(value, pymongo.dbref.DBRef):
+            # this.created_user.$id == "4c4c56f8cc1831418c000000"
+            op_js = '(this.%(field)s.$id == "%(id)s" &&'\
+                    ' this.%(field)s.$ref == "%(ref)s")' % {
+                        'field': key,
+                        'id': unicode(value.id),
+                        'ref': unicode(value.collection)
+                    }
+            value = None
+
         # Perform the substitution
         operation_js = op_js % {
             'field': key, 

tests/queryset.py

@@ -1304,6 +1304,20 @@ class QTest(unittest.TestCase):
 
         query = ['(', {'age__gte': 18}, '&&', {'name': 'test'}, ')']
         self.assertEqual((q1 & q2 & q3 & q4 & q5).query, query)
+    
+    def test_q_with_dbref(self):
+        """Ensure Q objects handle DBRefs correctly"""
+        class User(Document):
+            pass
+
+        class Post(Document):
+            created_user = ReferenceField(User)
+
+        user = User.objects.create()
+        Post.objects.create(created_user=user)
+
+        self.assertEqual(Post.objects.filter(created_user=user).count(), 1)
+        self.assertEqual(Post.objects.filter(Q(created_user=user)).count(), 1)
 
 if __name__ == '__main__':
     unittest.main()