Fixed #27710 -- Made Model.save() invalidate cached, stale relations after a primary key assignment.

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/many_to_one/tests.py b/tests/many_to_one/tests.py
index 0e3395bf3a..a2ff587ab3 100644
--- a/tests/many_to_one/tests.py
+++ b/tests/many_to_one/tests.py
@@ -656,3 +656,13 @@ class ManyToOneTests(TestCase):
         self.assertEqual(city.districts.count(), 2)
         city.districts.remove(d2)
         self.assertEqual(city.districts.count(), 1)
+
+    def test_cached_relation_invalidated_on_save(self):
+        """
+        Model.save() invalidates stale ForeignKey relations after a primary key
+        assignment.
+        """
+        self.assertEqual(self.a.reporter, self.r)  # caches a.reporter
+        self.a.reporter_id = self.r2.pk
+        self.a.save()
+        self.assertEqual(self.a.reporter, self.r2)