[1.7.x] Fixed #22466 -- ordering by reverse foreign key

Ordering by reverse foreign key was broken by custom lookups patch
(commit 20bab2cf9d).

Thanks to everybody who helped solving this issue. Special thanks to
Trac alias takis for reporting this.

Backport of 3b7c66a3ac from master

django/db/models/sql/query.py

@@ -1432,6 +1432,8 @@ class Query(object):
             alias = self.join(
                 connection, reuse=reuse, nullable=nullable, join_field=join.join_field)
             joins.append(alias)
+        if hasattr(final_field, 'field'):
+            final_field = final_field.field
         return final_field, targets, opts, joins, path
 
     def trim_joins(self, targets, joins, path):

tests/queries/tests.py

@@ -1396,6 +1396,18 @@ class Queries4Tests(BaseQuerysetTest):
         qs = Author.objects.order_by().order_by('name')
         self.assertTrue('ORDER BY' in qs.query.get_compiler(qs.db).as_sql()[0])
 
+    def test_order_by_reverse_fk(self):
+        # It is possible to order by reverse of foreign key, although that can lead
+        # to duplicate results.
+        c1 = SimpleCategory.objects.create(name="category1")
+        c2 = SimpleCategory.objects.create(name="category2")
+        CategoryItem.objects.create(category=c1)
+        CategoryItem.objects.create(category=c2)
+        CategoryItem.objects.create(category=c1)
+        self.assertQuerysetEqual(
+            SimpleCategory.objects.order_by('categoryitem', 'pk'),
+            [c1, c2, c1], lambda x: x)
+
     def test_ticket10181(self):
         # Avoid raising an EmptyResultSet if an inner query is probably
         # empty (and hence, not executed).