- Identified an inconsistency when handling :meth:`.Query.join` to the

same target more than once; it implicitly dedupes only in the case of
a relationship join, and due to :ticket:`3233`, in 1.0 a join
to the same table twice behaves differently than 0.9 in that it no
longer erroneously aliases.   To help document this change,
the verbiage regarding :ticket:`3233` in the migration notes has
been generalized, and a warning has been added when :meth:`.Query.join`
is called against the same target relationship more than once.
fixes #3367

1 files changed, 11 insertions, 0 deletions

diff --git a/test/orm/test_joins.py b/test/orm/test_joins.py
index 23d220dcc..540056dae 100644
--- a/test/orm/test_joins.py
+++ b/test/orm/test_joins.py
@@ -750,6 +750,17 @@ class JoinTest(QueryTest, AssertsCompiledSQL):
                 filter_by(id=3).outerjoin('orders','address').filter_by(id=1).all()
         assert [User(id=7, name='jack')] == result
 
+    def test_raises_on_dupe_target_rel(self):
+        User = self.classes.User
+
+        assert_raises_message(
+            sa.exc.SAWarning,
+            "Pathed join target Order.items has already been joined to; "
+            "skipping",
+            lambda: create_session().query(User).outerjoin('orders', 'items').\
+                outerjoin('orders', 'items')
+        )
+
     def test_from_joinpoint(self):
         Item, User, Order = (self.classes.Item,
                                 self.classes.User,