Mike Bayer committed 0821466

improved error message when a backref conflicts with a column-based property

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  • Parent commits 52f91f1

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File lib/sqlalchemy/orm/

             parent = prop.parent.primary_mapper()
             relation = cls(parent, prop.secondary, pj, sj, backref=prop.key, is_backref=True, **self.kwargs)
             mapper._compile_property(self.key, relation);
+        elif not isinstance(mapper.props[self.key], PropertyLoader):
+            raise exceptions.ArgumentError("Cant create backref '%s' on mapper '%s'; an incompatible property of that name already exists" % (self.key, str(mapper)))
             # else set one of us as the "backreference"
             parent = prop.parent.primary_mapper()

File test/orm/

+    def testpropconflict(self):
+        """test that a backref created against an existing mapper with a property name
+        conflict raises a decent error message"""
+        mapper(Address, addresses)
+        mapper(User, users,
+            properties={
+            'addresses':relation(Address, backref='email_address')
+        })
+        try:
+            class_mapper(Address)
+            class_mapper(User)
+            assert False
+        except exceptions.ArgumentError:
+            pass
     def testrefresh(self):
         mapper(User, users, properties={'addresses':relation(mapper(Address, addresses))})
         s = create_session()