Fixed #26486 -- Fixed a select_related() + defer() MTI edge case.

django/db/models/query_utils.py

@@ -256,7 +256,6 @@ def select_related_descend(field, restricted, requested, load_fields, reverse=Fa
                                    " and traversed using select_related"
                                    " at the same time." %
                                    (field.model._meta.object_name, field.name))
-            return False
     return True
 
 

tests/defer/tests.py

@@ -128,9 +128,8 @@ class DeferTests(AssertionMixin, TestCase):
             Primary.objects.only("name").select_related("related")[0]
 
     def test_defer_foreign_keys_are_deferred_and_not_traversed(self):
-        # With a depth-based select_related, all deferred ForeignKeys are
-        # deferred instead of traversed.
-        with self.assertNumQueries(3):
+        # select_related() overrides defer().
+        with self.assertNumQueries(1):
             obj = Primary.objects.defer("related").select_related()[0]
             self.assert_delayed(obj, 1)
             self.assertEqual(obj.related.id, self.s1.pk)

tests/select_related_onetoone/tests.py

@@ -1,7 +1,5 @@
 from __future__ import unicode_literals
 
-import unittest
-
 from django.core.exceptions import FieldError
 from django.test import SimpleTestCase, TestCase
 
@@ -175,7 +173,6 @@ class ReverseSelectRelatedTestCase(TestCase):
             self.assertEqual(p.child1.child4.value, p.child1.value)
             self.assertEqual(p.child1.child4.value4, 4)
 
-    @unittest.expectedFailure
     def test_inheritance_deferred(self):
         c = Child4.objects.create(name1='n1', name2='n2', value=1, value4=4)
         with self.assertNumQueries(1):
@@ -192,10 +189,9 @@ class ReverseSelectRelatedTestCase(TestCase):
         with self.assertNumQueries(1):
             self.assertEqual(p.child1.name2, 'n2')
 
-    @unittest.expectedFailure
     def test_inheritance_deferred2(self):
         c = Child4.objects.create(name1='n1', name2='n2', value=1, value4=4)
-        qs = Parent2.objects.select_related('child1', 'child4').only(
+        qs = Parent2.objects.select_related('child1', 'child1__child4').only(
             'id2', 'child1__value', 'child1__child4__value4')
         with self.assertNumQueries(1):
             p = qs.get(name2="n2")
@@ -207,9 +203,8 @@ class ReverseSelectRelatedTestCase(TestCase):
         with self.assertNumQueries(1):
             self.assertEqual(p.child1.name2, 'n2')
         p = qs.get(name2="n2")
-        with self.assertNumQueries(1):
+        with self.assertNumQueries(0):
             self.assertEqual(p.child1.name1, 'n1')
-        with self.assertNumQueries(1):
             self.assertEqual(p.child1.child4.name1, 'n1')