- Fixed issue where post_update on a many-to-one relationship would

fail to emit an UPDATE in the case where the attribute were set to
None and not previously loaded.
fixes #3599

1 files changed, 34 insertions, 1 deletions

diff --git a/test/orm/test_cycles.py b/test/orm/test_cycles.py
index 56386e8d2..b5c1b6467 100644
--- a/test/orm/test_cycles.py
+++ b/test/orm/test_cycles.py
@@ -10,7 +10,7 @@ from sqlalchemy import Integer, String, ForeignKey
 from sqlalchemy.testing.schema import Table, Column
 from sqlalchemy.orm import mapper, relationship, backref, \
                             create_session, sessionmaker
-from sqlalchemy.testing import eq_
+from sqlalchemy.testing import eq_, is_
 from sqlalchemy.testing.assertsql import RegexSQL, CompiledSQL, AllOf
 from sqlalchemy.testing import fixtures
 
@@ -816,6 +816,39 @@ class OneToManyManyToOneTest(fixtures.MappedTest):
                          {'id': b4.id}])
         )
 
+    def test_post_update_m2o_detect_none(self):
+        person, ball, Ball, Person = (
+            self.tables.person,
+            self.tables.ball,
+            self.classes.Ball,
+            self.classes.Person)
+
+        mapper(Ball, ball, properties={
+            'person': relationship(
+                Person, post_update=True,
+                primaryjoin=person.c.id == ball.c.person_id)
+        })
+        mapper(Person, person)
+
+        sess = create_session(autocommit=False, expire_on_commit=True)
+        sess.add(Ball(person=Person()))
+        sess.commit()
+        b1 = sess.query(Ball).first()
+
+        # needs to be unloaded
+        assert 'person' not in b1.__dict__
+        b1.person = None
+
+        self.assert_sql_execution(
+            testing.db,
+            sess.flush,
+            CompiledSQL(
+                "UPDATE ball SET person_id=:person_id WHERE ball.id = :ball_id",
+                lambda ctx: {'person_id': None, 'ball_id': b1.id})
+        )
+
+        is_(b1.person, None)
+
 
 class SelfReferentialPostUpdateTest(fixtures.MappedTest):
     """Post_update on a single self-referential mapper.