[1.8.x] Fixed #25715 -- Fixed Model.refresh_from_db() with ForeignKey w/on_delete=SET_NULL.

Backport of 54e2e688e1cfbdb37dfa5dd3b3ffdf2af12b4423 from master

2 files changed, 12 insertions, 0 deletions

diff --git a/tests/basic/models.py b/tests/basic/models.py
index 86d0f0c4e4..0ebe3e0b4a 100644
--- a/tests/basic/models.py
+++ b/tests/basic/models.py
@@ -30,6 +30,7 @@ class ArticleSelectOnSave(Article):
 class SelfRef(models.Model):
     selfref = models.ForeignKey('self', null=True, blank=True,
                                 related_name='+')
+    article = models.ForeignKey(Article, on_delete=models.SET_NULL, null=True, blank=True)
 
     def __str__(self):
         # This method intentionally doesn't work for all cases - part
diff --git a/tests/basic/tests.py b/tests/basic/tests.py
index e5c70b22e3..3f420d427b 100644
--- a/tests/basic/tests.py
+++ b/tests/basic/tests.py
@@ -767,6 +767,17 @@ class ModelRefreshTests(TestCase):
         self.assertEqual(a2.pub_date, pub_date)
         self.assertEqual(a2._state.db, "default")
 
+    def test_refresh_fk_on_delete_set_null(self):
+        a = Article.objects.create(
+            headline='Parrot programs in Python',
+            pub_date=datetime(2005, 7, 28),
+        )
+        s1 = SelfRef.objects.create(article=a)
+        a.delete()
+        s1.refresh_from_db()
+        self.assertIsNone(s1.article_id)
+        self.assertIsNone(s1.article)
+
     def test_refresh_no_fields(self):
         a = Article.objects.create(pub_date=self._truncate_ms(datetime.now()))
         with self.assertNumQueries(0):