Fixed #20378 -- regression in GenericRelation on abstract model

When a GenericRelation was defined on abstract model, queries on childs
of the abstract model didn't work. The problem was in the way fields and
in particular field.rel was copied from models to their children.

The regression was likely caused by #19385. Thanks to Gavin Wahl for
spotting the regression.

3 files changed, 30 insertions, 1 deletions

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 13cec1bfba..7d01391d4f 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -157,6 +157,8 @@ class Field(object):
         obj = copy.copy(self)
         if self.rel:
             obj.rel = copy.copy(self.rel)
+            if hasattr(self.rel, 'field') and self.rel.field is self:
+                obj.rel.field = obj
         memodict[id(self)] = obj
         return obj
 
diff --git a/tests/generic_relations_regress/models.py b/tests/generic_relations_regress/models.py
index 2795471f7f..206dbe02b0 100644
--- a/tests/generic_relations_regress/models.py
+++ b/tests/generic_relations_regress/models.py
@@ -122,3 +122,12 @@ class Tag(models.Model):
 
 class Board(models.Model):
     name = models.CharField(primary_key=True, max_length=15)
+
+class HasLinks(models.Model):
+    links = generic.GenericRelation(Link)
+
+    class Meta:
+        abstract = True
+
+class HasLinkThing(HasLinks):
+    pass
diff --git a/tests/generic_relations_regress/tests.py b/tests/generic_relations_regress/tests.py
index 474113584a..519ca203a9 100644
--- a/tests/generic_relations_regress/tests.py
+++ b/tests/generic_relations_regress/tests.py
@@ -4,7 +4,7 @@ from django.test import TestCase, skipIfDBFeature
 
 from .models import (Address, Place, Restaurant, Link, CharLink, TextLink,
     Person, Contact, Note, Organization, OddRelation1, OddRelation2, Company,
-    Developer, Team, Guild, Tag, Board)
+    Developer, Team, Guild, Tag, Board, HasLinkThing)
 
 
 class GenericRelationTests(TestCase):
@@ -135,3 +135,21 @@ class GenericRelationTests(TestCase):
         b1 = Board.objects.create(name='')
         tag = Tag(label='VP', content_object=b1)
         tag.save()
+
+    def test_ticket_20378(self):
+        hs1 = HasLinkThing.objects.create()
+        hs2 = HasLinkThing.objects.create()
+        l1 = Link.objects.create(content_object=hs1)
+        l2 = Link.objects.create(content_object=hs2)
+        self.assertQuerysetEqual(
+            HasLinkThing.objects.filter(links=l1),
+            [hs1], lambda x: x)
+        self.assertQuerysetEqual(
+            HasLinkThing.objects.filter(links=l2),
+            [hs2], lambda x: x)
+        self.assertQuerysetEqual(
+            HasLinkThing.objects.exclude(links=l2),
+            [hs1], lambda x: x)
+        self.assertQuerysetEqual(
+            HasLinkThing.objects.exclude(links=l1),
+            [hs2], lambda x: x)