From a4055adf702d086334a9ab2ca25a5e41e896a4fb Mon Sep 17 00:00:00 2001
From: Vinny Do <vdo.code@gmail.com>
Date: Tue, 16 Apr 2019 17:49:16 +1000
Subject: [PATCH] Fixed #30368 -- Fixed prefetch_related() for
 GenericForeignKey when PK is also a FK.

---
 AUTHORS                            | 1 +
 django/db/models/fields/related.py | 3 +++
 tests/prefetch_related/tests.py    | 7 +++++++
 3 files changed, 11 insertions(+)

diff --git a/AUTHORS b/AUTHORS
index 96d0696dd1..0557c343db 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -880,6 +880,7 @@ answer newbie questions, and generally made Django that much better:
     Vinay Karanam <https://github.com/vinayinvicible>
     Vinay Sajip <vinay_sajip@yahoo.co.uk>
     Vincent Foley <vfoleybourgon@yahoo.ca>
+    Vinny Do <vdo.code@gmail.com>
     Vitaly Babiy <vbabiy86@gmail.com>
     Vladimir Kuzma <vladimirkuzma.ch@gmail.com>
     Vlado <vlado@labath.org>
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index eda09c2ebe..2eb802e570 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -939,6 +939,9 @@ class ForeignKey(ForeignObject):
     def get_db_prep_value(self, value, connection, prepared=False):
         return self.target_field.get_db_prep_value(value, connection, prepared)
 
+    def get_prep_value(self, value):
+        return self.target_field.get_prep_value(value)
+
     def contribute_to_related_class(self, cls, related):
         super().contribute_to_related_class(cls, related)
         if self.remote_field.field_name is None:
diff --git a/tests/prefetch_related/tests.py b/tests/prefetch_related/tests.py
index a32ac81d12..0b3caed0dc 100644
--- a/tests/prefetch_related/tests.py
+++ b/tests/prefetch_related/tests.py
@@ -891,6 +891,13 @@ class GenericRelationTests(TestCase):
         qs = Comment.objects.prefetch_related('content_object_uuid')
         self.assertEqual([c.content_object_uuid for c in qs], [article])
 
+    def test_prefetch_GFK_fk_pk(self):
+        book = Book.objects.create(title='Poems')
+        book_with_year = BookWithYear.objects.create(book=book, published_year=2019)
+        Comment.objects.create(comment='awesome', content_object=book_with_year)
+        qs = Comment.objects.prefetch_related('content_object')
+        self.assertEqual([c.content_object for c in qs], [book_with_year])
+
     def test_traverse_GFK(self):
         """
         A 'content_object' can be traversed with prefetch_related() and