Fixes DBRef handling in _delta

refs: hmarr/mongoengine#518

mongoengine/base.py

@@ -1043,11 +1043,16 @@ Invalid data to create a `%s` instance.\n%s""".strip() % (cls._class_name, error
             for path in set_fields:
                 parts = path.split('.')
                 d = doc
+                new_path = []
                 for p in parts:
-                    if p.isdigit():
+                    if isinstance(d, DBRef):
+                        break
+                    elif p.isdigit():
                         d = d[int(p)]
-                    else:
+                    elif hasattr(d, 'get'):
                         d = d.get(p)
+                    new_path.append(p)
+                path = '.'.join(new_path)
                 set_data[path] = d
         else:
             set_data = doc

mongoengine/document.py

@@ -226,7 +226,7 @@ class Document(BaseDocument):
                 if cascade_kwargs:  # Allow granular control over cascades
                     kwargs.update(cascade_kwargs)
                 kwargs['_refs'] = _refs
-                self._changed_fields = []
+                #self._changed_fields = []
                 self.cascade_save(**kwargs)
 
         except pymongo.errors.OperationFailure, err:
@@ -246,6 +246,7 @@ class Document(BaseDocument):
         """Recursively saves any references / generic references on an object"""
         from fields import ReferenceField, GenericReferenceField
         _refs = kwargs.get('_refs', []) or []
+
         for name, cls in self._fields.items():
             if not isinstance(cls, (ReferenceField, GenericReferenceField)):
                 continue