GenericForeignKey.__get__ use cached value even value is None

django/contrib/contenttypes/fields.py

@@ -228,6 +228,8 @@ def __get__(self, instance, cls=None):
         pk_val = getattr(instance, self.fk_field)
 
         rel_obj = self.get_cached_value(instance, default=None)
+        if rel_obj is None and self.is_cached(instance):
+            return rel_obj
         if rel_obj is not None:
             ct_match = ct_id == self.get_content_type(obj=rel_obj, using=instance._state.db).id
             pk_match = rel_obj._meta.pk.to_python(pk_val) == rel_obj.pk

tests/contenttypes_tests/models.py

@@ -97,6 +97,13 @@ class Meta:
         order_with_respect_to = 'parent'
 
 
+class AuditLog(models.Model):
+    message = models.CharField(max_length=200)
+    content_type = models.ForeignKey(ContentType, models.CASCADE, null=True)
+    object_id = models.PositiveIntegerField(null=True)
+    object = GenericForeignKey()
+
+
 class ModelWithNullFKToSite(models.Model):
     title = models.CharField(max_length=200)
     site = models.ForeignKey(Site, null=True, on_delete=models.CASCADE)

tests/contenttypes_tests/test_fields.py

@@ -2,14 +2,14 @@
 
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.db import models
-from django.test import SimpleTestCase, TestCase
+from django.test import TestCase
 from django.test.utils import isolate_apps
 
-from .models import Answer, Question
+from .models import Answer, AuditLog, Question
 
 
 @isolate_apps('contenttypes_tests')
-class GenericForeignKeyTests(SimpleTestCase):
+class GenericForeignKeyTests(TestCase):
 
     def test_str(self):
         class Model(models.Model):
@@ -24,6 +24,18 @@ def test_incorrect_get_prefetch_queryset_arguments(self):
         with self.assertRaisesMessage(ValueError, "Custom queryset can't be used for this lookup."):
             Answer.question.get_prefetch_queryset(Answer.objects.all(), Answer.objects.all())
 
+    def test_get_object_cache_respects_deleted_objects(self):
+        question = Question.objects.create(text="test")
+        question_pk = question.pk
+        log = AuditLog.objects.create(message="Created", object=question)
+        Question.objects.all().delete()
+
+        log = AuditLog.objects.get(message="Created")
+        with self.assertNumQueries(1):
+            self.assertEqual(log.object_id, question_pk)
+            self.assertIsNone(log.object)
+            self.assertIsNone(log.object)
+
 
 class GenericRelationTests(TestCase):
 

tests/prefetch_related/tests.py

@@ -1041,8 +1041,8 @@ def test_deleted_object_GFK(self):
         book1_pk = self.book1.pk
         self.book1.delete()
 
-        with self.assertNumQueries(3):
-            qs = TaggedItem.objects.filter(tag='awesome').prefetch_related('content_object')
+        with self.assertNumQueries(2):
+            qs = TaggedItem.objects.filter(tag="awesome").prefetch_related("content_object")
             result = [(t.object_id, t.content_type_id, t.content_object) for t in qs]
             self.assertEqual(result, [
                 (book1_pk, ct.pk, None),