Refs #27222 -- Restored Model.save()'s refreshing of db_returning fields even if a value is set.

The logic could likely be adjusted to assign the pre_save value in most cases
to avoid the database transit but it could break in subtle ways so it's not
worth the complexity it would require.

Regression in 9468043.

Co-authored-by: Tim Graham <timograham@gmail.com>

Author: 2 people

django/db/models/base.py

@@ -1142,23 +1142,30 @@ def _save_table(
                         ),
                     )["_order__max"]
                 )
-            fields = [
+            insert_fields = [
                 f
                 for f in meta.local_concrete_fields
                 if not f.generated and (pk_set or f is not meta.auto_field)
             ]
             returning_fields = list(meta.db_returning_fields)
-            for field in fields:
+            can_return_columns_from_insert = connections[
+                using
+            ].features.can_return_columns_from_insert
+            for field in insert_fields:
                 value = (
                     getattr(self, field.attname) if raw else field.pre_save(self, False)
                 )
                 if hasattr(value, "resolve_expression"):
                     if field not in returning_fields:
                         returning_fields.append(field)
-                elif field.db_returning:
+                elif (
+                    field.db_returning
+                    and not can_return_columns_from_insert
+                    and not (pk_set and field is meta.auto_field)
+                ):
                     returning_fields.remove(field)
             results = self._do_insert(
-                cls._base_manager, using, fields, returning_fields, raw
+                cls._base_manager, using, insert_fields, returning_fields, raw
             )
             if results:
                 self._assign_returned_values(results[0], returning_fields)

tests/basic/tests.py

@@ -215,6 +215,14 @@ def test_save_primary_with_falsey_db_default(self):
         with self.assertNumQueries(1):
             PrimaryKeyWithFalseyDbDefault().save()
 
+    def test_auto_field_with_value_refreshed(self):
+        """
+        An auto field must be refreshed by Model.save() even when a value is
+        set because the database may return a value of a different type.
+        """
+        a = Article.objects.create(pk="123456", pub_date=datetime(2025, 9, 16))
+        self.assertEqual(a.pk, 123456)
+
 
 class ModelTest(TestCase):
     def test_objects_attribute_is_only_available_on_the_class_itself(self):

tests/queries/test_db_returning.py

@@ -26,6 +26,11 @@ def test_insert_returning_non_integer(self):
         self.assertTrue(obj.created)
         self.assertIsInstance(obj.created, datetime.datetime)
 
+    def test_insert_returning_non_integer_from_literal_value(self):
+        obj = NonIntegerPKReturningModel.objects.create(pk="2025-01-01")
+        self.assertTrue(obj.created)
+        self.assertIsInstance(obj.created, datetime.datetime)
+
     def test_insert_returning_multiple(self):
         with CaptureQueriesContext(connection) as captured_queries:
             obj = ReturningModel.objects.create()