Fixed #28147 -- Fixed loss of assigned parent when saving child after parent.

Thanks Erwin Junge for the initial patch.

2 files changed, 14 insertions, 2 deletions

diff --git a/tests/many_to_one/models.py b/tests/many_to_one/models.py
index 96b84ccddb..6230129bbd 100644
--- a/tests/many_to_one/models.py
+++ b/tests/many_to_one/models.py
@@ -70,6 +70,10 @@ class Child(models.Model):
     parent = models.ForeignKey(Parent, models.CASCADE)
 
 
+class ChildNullableParent(models.Model):
+    parent = models.ForeignKey(Parent, models.CASCADE, null=True)
+
+
 class ToFieldChild(models.Model):
     parent = models.ForeignKey(Parent, models.CASCADE, to_field='name', related_name='to_field_children')
 
diff --git a/tests/many_to_one/tests.py b/tests/many_to_one/tests.py
index 8ad467b6b6..7538f238f2 100644
--- a/tests/many_to_one/tests.py
+++ b/tests/many_to_one/tests.py
@@ -8,8 +8,8 @@ from django.test import TestCase
 from django.utils.translation import gettext_lazy
 
 from .models import (
-    Article, Category, Child, City, District, First, Parent, Record, Relation,
-    Reporter, School, Student, Third, ToFieldChild,
+    Article, Category, Child, ChildNullableParent, City, District, First,
+    Parent, Record, Relation, Reporter, School, Student, Third, ToFieldChild,
 )
 
 
@@ -522,6 +522,14 @@ class ManyToOneTests(TestCase):
         self.assertIsNot(c.parent, p)
         self.assertEqual(c.parent, p)
 
+    def test_save_nullable_fk_after_parent(self):
+        parent = Parent()
+        child = ChildNullableParent(parent=parent)
+        parent.save()
+        child.save()
+        child.refresh_from_db()
+        self.assertEqual(child.parent, parent)
+
     def test_save_nullable_fk_after_parent_with_to_field(self):
         parent = Parent(name='jeff')
         child = ToFieldChild(parent=parent)