[4.2.x] Fixed #34612 -- Fixed QuerySet.only() crash on reverse relationships.

Regression in b3db6c8dcb5145f7d45eff517bcd96460475c879.

Thanks Ian Cubitt for the report.

This also corrected test_inheritance_deferred2() test which was
previously properly defined and marked as an expected failure but was
then wrongly adjusted to mask the lack of support for per-alias
deferral that was fixed by #21204.

Backport of 2cf76f2d5d1aa16acfadaf53db3d30128a34b088 from main

2 files changed, 13 insertions, 0 deletions

diff --git a/tests/defer_regress/tests.py b/tests/defer_regress/tests.py
index ab2be085c6..0d389777a1 100644
--- a/tests/defer_regress/tests.py
+++ b/tests/defer_regress/tests.py
@@ -203,6 +203,16 @@ class DeferRegressionTest(TestCase):
             self.assertEqual(i.one_to_one_item.name, "second")
         with self.assertNumQueries(1):
             self.assertEqual(i.value, 42)
+        with self.assertNumQueries(1):
+            i = Item.objects.select_related("one_to_one_item").only(
+                "name", "one_to_one_item__item"
+            )[0]
+            self.assertEqual(i.one_to_one_item.pk, o2o.pk)
+            self.assertEqual(i.name, "first")
+        with self.assertNumQueries(1):
+            self.assertEqual(i.one_to_one_item.name, "second")
+        with self.assertNumQueries(1):
+            self.assertEqual(i.value, 42)
 
     def test_defer_with_select_related(self):
         item1 = Item.objects.create(name="first", value=47)
diff --git a/tests/select_related_onetoone/tests.py b/tests/select_related_onetoone/tests.py
index 8bdfb83fe8..83462ed071 100644
--- a/tests/select_related_onetoone/tests.py
+++ b/tests/select_related_onetoone/tests.py
@@ -249,6 +249,9 @@ class ReverseSelectRelatedTestCase(TestCase):
             self.assertEqual(p.child1.name2, "n2")
         p = qs.get(name2="n2")
         with self.assertNumQueries(0):
+            self.assertEqual(p.child1.value, 1)
+            self.assertEqual(p.child1.child4.value4, 4)
+        with self.assertNumQueries(2):
             self.assertEqual(p.child1.name1, "n1")
             self.assertEqual(p.child1.child4.name1, "n1")