Fixed #24002 -- GenericRelation filtering targets related model's pk

Previously Publisher.objects.filter(book=val) would target
book.object_id if book is a GenericRelation. This is inconsistent to
filtering over reverse foreign key relations, where the target is the
related model's primary key.

django/contrib/contenttypes/fields.py

@@ -307,7 +307,7 @@ class GenericRelation(ForeignObject):
 
     def get_path_info(self):
         opts = self.rel.to._meta
-        target = opts.get_field_by_name(self.object_id_field_name)[0]
+        target = opts.pk
         return [PathInfo(self.model._meta, opts, (target,), self.rel, True, False)]
 
     def get_reverse_path_info(self):

tests/generic_relations_regress/tests.py

@@ -220,15 +220,18 @@ class GenericRelationTests(TestCase):
 
     def test_annotate(self):
         hs1 = HasLinkThing.objects.create()
+        hs2 = HasLinkThing.objects.create()
+        HasLinkThing.objects.create()
         b = Board.objects.create(name=str(hs1.pk))
+        Link.objects.create(content_object=hs2)
         l = Link.objects.create(content_object=hs1)
         Link.objects.create(content_object=b)
-        qs = HasLinkThing.objects.annotate(Sum('links'))
+        qs = HasLinkThing.objects.annotate(Sum('links')).filter(pk=hs1.pk)
         # If content_type restriction isn't in the query's join condition,
         # then wrong results are produced here as the link to b will also match
         # (b and hs1 have equal pks).
         self.assertEqual(qs.count(), 1)
-        self.assertEqual(qs[0].links__sum, hs1.id)
+        self.assertEqual(qs[0].links__sum, l.id)
         l.delete()
         # Now if we don't have proper left join, we will not produce any
         # results at all here.
@@ -241,6 +244,15 @@ class GenericRelationTests(TestCase):
         self.assertEqual(qs.filter(links__sum__isnull=True).count(), 1)
         self.assertEqual(qs.filter(links__sum__isnull=False).count(), 0)
 
+    def test_filter_targets_related_pk(self):
+        HasLinkThing.objects.create()
+        hs2 = HasLinkThing.objects.create()
+        l = Link.objects.create(content_object=hs2)
+        self.assertNotEqual(l.object_id, l.pk)
+        self.assertQuerysetEqual(
+            HasLinkThing.objects.filter(links=l.pk),
+            [hs2], lambda x: x)
+
     def test_editable_generic_rel(self):
         GenericRelationForm = modelform_factory(HasLinkThing, fields='__all__')
         form = GenericRelationForm()