- merged r6553 from trunk

- Session.merge() now properly overwrites a many-to-one or
uselist=False attribute to None if the attribute
is also None in the given object to be merged.

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index e874e3747..e3ecad3b1 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -665,11 +665,13 @@ class RelationProperty(StrategizedProperty):
             if current is not None:
                 _recursive[(current, self)] = True
                 obj = session._merge(current, dont_load=dont_load, _recursive=_recursive)
-                if obj is not None:
-                    if dont_load:
-                        dest_state.dict[self.key] = obj
-                    else:
-                        setattr(dest, self.key, obj)
+            else:
+                obj = None
+            
+            if dont_load:
+                dest_state.dict[self.key] = obj
+            else:
+                setattr(dest, self.key, obj)
 
     def cascade_iterator(self, type_, state, visited_instances, halt_on=None):
         if not type_ in self.cascade: