[5.2.x] Fixed #36135 -- Fixed reverse GenericRelation prefetching.

The get_(local|foreign)_related_value methods of GenericRelation must be
reversed because it defines (from|to)_fields and associated related_fields
in the reversed order as it's effectively a reverse GenericForeignKey
itself.

The related value methods must also account for the fact that referenced
primary key values might be stored as a string on the model defining the
GenericForeignKey but as integer on the model defining the GenericRelation.
This is achieved by calling the to_python method of the involved content type
in get_foreign_related_value just like GenericRelatedObjectManager does.

Lastly reverse many-to-one manager's prefetch_related_querysets should use
set_cached_value instead of direct attribute assignment as direct assignment
might are disallowed on ReverseManyToOneDescriptor descriptors. This is likely
something that was missed in f5233dc (refs #32511) when the is_cached guard
was added.

Thanks 1xinghuan for the report.

Backport of 198b30168d4e94af42e0dc7967bd3259b5c5790b from main.

1 files changed, 14 insertions, 0 deletions

diff --git a/tests/prefetch_related/tests.py b/tests/prefetch_related/tests.py
index 856f766d30..99e3cd6b80 100644
--- a/tests/prefetch_related/tests.py
+++ b/tests/prefetch_related/tests.py
@@ -1257,6 +1257,20 @@ class GenericRelationTests(TestCase):
                 ],
             )
 
+    def test_reverse_generic_relation(self):
+        # Create two distinct bookmarks to ensure the bookmark and
+        # tagged item models primary are offset.
+        first_bookmark = Bookmark.objects.create()
+        second_bookmark = Bookmark.objects.create()
+        TaggedItem.objects.create(
+            content_object=first_bookmark, favorite=second_bookmark
+        )
+        with self.assertNumQueries(2):
+            obj = TaggedItem.objects.prefetch_related("favorite_bookmarks").get()
+        with self.assertNumQueries(0):
+            prefetched_bookmarks = obj.favorite_bookmarks.all()
+            self.assertQuerySetEqual(prefetched_bookmarks, [second_bookmark])
+
 
 class MultiTableInheritanceTest(TestCase):
     @classmethod