[4.2.x] Fixed #34570 -- Silenced noop deferral of many-to-many and GFK.

While deferring many-to-many and GFK has no effect, the previous
implementation of QuerySet.defer() ignore them instead of crashing.

Regression in b3db6c8dcb5145f7d45eff517bcd96460475c879.

Thanks Paco Martínez for the report.

Backport of 99e5dff737cd20b12d060e4794e097063b61ec40 from main

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/defer_regress/tests.py b/tests/defer_regress/tests.py
index 9f94d5fac1..ab2be085c6 100644
--- a/tests/defer_regress/tests.py
+++ b/tests/defer_regress/tests.py
@@ -296,6 +296,12 @@ class DeferRegressionTest(TestCase):
         with self.assertNumQueries(1):
             self.assertEqual(leaf.second_child.value, 64)
 
+    def test_defer_many_to_many_ignored(self):
+        location = Location.objects.create()
+        request = Request.objects.create(location=location)
+        with self.assertNumQueries(1):
+            self.assertEqual(Request.objects.defer("items").get(), request)
+
 
 class DeferDeletionSignalsTests(TestCase):
     senders = [Item, Proxy]