refresh_from_db() doesn't refresh ForeignObject relations

[Jacob Walls]

Although it's an internal API ForeignObject is now ​quasi-public. When trying it out in a non-composite-pk situation I found that refresh_from_db() didn't clear out a related ForeignObject.

Here is a rough test using the composite_pk models (EDIT: prior version of test wasn't demonstrating anything):

tests/composite_pk/test_models.py

@@ -155 +155 @@
         self.assertEqual(4, token.permission_set.count())
         self.assertEqual(4, user.permission_set.count())
         self.assertEqual(4, comment.permission_set.count())
+
+    def test_refresh_foreign_object(self):
+        self.comment_1.user = None
+        self.comment_1.refresh_from_db()
+        self.assertEqual(self.comment_1.user, self.user_1)

---

E
======================================================================
ERROR: test_refresh_foreign_object (composite_pk.test_models.CompositePKModelsTests.test_refresh_foreign_object)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/.../django/tests/composite_pk/test_models.py", line 161, in test_refresh_foreign_object
    self.comment_1.refresh_from_db()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/.../py313/lib/python3.13/site-packages/django/db/models/base.py", line 737, in refresh_from_db
    db_instance = db_instance_qs.get()
  File "/Users/.../py313/lib/python3.13/site-packages/django/db/models/query.py", line 633, in get
    raise self.model.DoesNotExist(
        "%s matching query does not exist." % self.model._meta.object_name
    )
composite_pk.models.tenant.Comment.DoesNotExist: Comment matching query does not exist.

----------------------------------------------------------------------
Ran 1 test in 0.008s

FAILED (errors=1)

[Jacob Walls]

The variant where I found this didn't cause refresh_from_db() to throw, it just silently kept the old value. (This was with a nullable ForeignObject.)