From: Sebastian Bank <sebastian.bank@uni-leipzig.de>
Date: Thu, 4 Dec 2014 13:34:08 +0000 (+0100)
Subject: warn on duplicate polymorphic_identity
X-Git-Tag: rel_1_0_0b1~93^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0e61acaf145f57c78a13fc5c20052e24472cfb02;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

warn on duplicate polymorphic_identity
---

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 863dab5cbf..0e0c1a8337 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -974,6 +974,15 @@ class Mapper(InspectionAttr):
             self._all_tables = self.inherits._all_tables
 
             if self.polymorphic_identity is not None:
+                if self.polymorphic_identity in self.polymorphic_map:
+                    util.warn(
+                        "Reassigning polymorphic association for identity %r "
+                        "from %r to %r: Check for duplicate use of %r as "
+                        "value for polymorphic_identity." %
+                        (self.polymorphic_identity,
+                         self.polymorphic_map[self.polymorphic_identity],
+                         self, self.polymorphic_identity)
+                )
                 self.polymorphic_map[self.polymorphic_identity] = self
 
         else:
diff --git a/test/orm/test_mapper.py b/test/orm/test_mapper.py
index 63ba1a207f..264b386d48 100644
--- a/test/orm/test_mapper.py
+++ b/test/orm/test_mapper.py
@@ -716,6 +716,19 @@ class MapperTest(_fixtures.FixtureTest, AssertsCompiledSQL):
             m3.identity_key_from_instance(AddressUser())
         )
 
+    def test_reassign_polymorphic_identity_warns(self):
+        User = self.classes.User
+        users = self.tables.users
+        class MyUser(User):
+            pass
+        m1 = mapper(User, users, polymorphic_on=users.c.name,
+                    polymorphic_identity='user')
+        assert_raises_message(
+            sa.exc.SAWarning,
+            "Reassigning polymorphic association for identity 'user'",
+            mapper,
+            MyUser, users, inherits=User, polymorphic_identity='user'
+        )
 
 
     def test_illegal_non_primary(self):