Refs #28723 -- Fixed stale prefetch_related cache after add/remove.

Regression in 514b2c989a.

django/db/models/fields/related_descriptors.py

@@ -575,7 +575,7 @@ def create_reverse_many_to_one_manager(superclass, rel):
 
         def _remove_prefetched_objects(self):
             try:
-                self.instance._prefetched_objects_cache.pop(self.field.related_query_name())
+                self.instance._prefetched_objects_cache.pop(self.field.remote_field.get_cache_name())
             except (AttributeError, KeyError):
                 pass  # nothing to clear from cache
 

tests/prefetch_related/models.py

@@ -86,7 +86,8 @@ class Reader(models.Model):
 
 
 class BookReview(models.Model):
-    book = models.ForeignKey(BookWithYear, models.CASCADE)
+    # Intentionally does not have a related name.
+    book = models.ForeignKey(BookWithYear, models.CASCADE, null=True)
     notes = models.TextField(null=True, blank=True)
 
 

tests/prefetch_related/tests.py

@@ -1415,6 +1415,21 @@ class DirectPrefechedObjectCacheReuseTests(TestCase):
         with self.assertNumQueries(0):
             prefetch_related_objects([bookwithyear1], 'bookreview_set')
 
+    def test_add_clears_prefetched_objects(self):
+        bookwithyear = BookWithYear.objects.get(pk=self.bookwithyear1.pk)
+        prefetch_related_objects([bookwithyear], 'bookreview_set')
+        self.assertCountEqual(bookwithyear.bookreview_set.all(), [self.bookreview1])
+        new_review = BookReview.objects.create()
+        bookwithyear.bookreview_set.add(new_review)
+        self.assertCountEqual(bookwithyear.bookreview_set.all(), [self.bookreview1, new_review])
+
+    def test_remove_clears_prefetched_objects(self):
+        bookwithyear = BookWithYear.objects.get(pk=self.bookwithyear1.pk)
+        prefetch_related_objects([bookwithyear], 'bookreview_set')
+        self.assertCountEqual(bookwithyear.bookreview_set.all(), [self.bookreview1])
+        bookwithyear.bookreview_set.remove(self.bookreview1)
+        self.assertCountEqual(bookwithyear.bookreview_set.all(), [])
+
 
 class ReadPrefetchedObjectsCacheTests(TestCase):
     @classmethod