warn when two classes with the same name end up in the declarative registry

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/sqlalchemy/ext/declarative.py b/lib/sqlalchemy/ext/declarative.py
index 586067527..57dff857c 100755
--- a/lib/sqlalchemy/ext/declarative.py
+++ b/lib/sqlalchemy/ext/declarative.py
@@ -1046,6 +1046,13 @@ def _as_declarative(cls, classname, dict_):
     for k, v in mapper_args.iteritems():
         mapper_args[k] = column_copies.get(v,v)
     
+
+    if classname in cls._decl_class_registry:
+        util.warn("The classname %r is already in the registry of this"
+                  " declarative base, mapped to %r" % (
+                classname,
+                cls._decl_class_registry[classname]
+                ))
     cls._decl_class_registry[classname] = cls
     our_stuff = util.OrderedDict()