Fixed #37036 -- Added missing flat=True arg in DeferredAttribute.fetch_many().

Author: garybadwal

AUTHORS

@@ -422,6 +422,7 @@ answer newbie questions, and generally made Django that much better:
     Grzegorz Ślusarek <grzegorz.slusarek@gmail.com>
     Guilherme Mesquita Gondim <semente@taurinus.org>
     Guillaume Pannatier <guillaume.pannatier@gmail.com>
+    Gurpreet Singh <https://www.garybadwal.com/>
     Gustavo Picon
     hambaloney
     Hang Park <hangpark@kaist.ac.kr>

django/db/models/query_utils.py

@@ -296,7 +296,7 @@ def fetch_many(self, instances):
         db = instances[0]._state.db
         value_by_pk = (
             self.field.model._base_manager.using(db)
-            .values_list(attname)
+            .values_list(attname, flat=True)
             .in_bulk({i.pk for i in instances})
         )
         for instance in instances:

tests/defer/tests.py

@@ -219,6 +219,20 @@ def test_defer_fetch_mode_fetch_peers_single(self):
         with self.assertNumQueries(1):
             p1.value
 
+    def test_defer_fk_fetch_mode_fetch_peers(self):
+        p1, p2 = Primary.objects.fetch_mode(FETCH_PEERS).defer("related")
+        with self.assertNumQueries(2):
+            self.assertEqual(p1.related, self.s1)
+        with self.assertNumQueries(0):
+            self.assertEqual(p2.related, self.s1)
+
+    def test_only_fk_fetch_mode_fetch_peers(self):
+        p1, p2 = Primary.objects.fetch_mode(FETCH_PEERS).only("name")
+        with self.assertNumQueries(2):
+            self.assertEqual(p1.related, self.s1)
+        with self.assertNumQueries(0):
+            self.assertEqual(p2.related, self.s1)
+
     def test_only_fetch_mode_raise(self):
         p1 = Primary.objects.fetch_mode(RAISE).only("name").get(name="p1")
         msg = "Fetching of Primary.value blocked."

tests/many_to_one/tests.py

@@ -1002,3 +1002,16 @@ def test_fetch_mode_copied_reverse_fetching_many(self):
             a2._state.fetch_mode,
             FETCH_PEERS,
         )
+
+    def test_fetch_mode_fetch_peers_reverse_with_deferred_fk(self):
+        Article.objects.create(
+            headline="Another article",
+            pub_date=datetime.date(2005, 7, 27),
+            reporter=self.r,
+        )
+        r = Reporter.objects.fetch_mode(FETCH_PEERS).get(pk=self.r.pk)
+        a1, a2 = r.article_set.defer("reporter")
+        with self.assertNumQueries(2):
+            self.assertEqual(a1.reporter, self.r)
+        with self.assertNumQueries(0):
+            self.assertEqual(a2.reporter, self.r)