Fixed #33579 -- Specialized exception raised on forced update failures.

Raising DatabaseError directly made it harder than it should to
differentiate between IntegrityError when a forced update resulted in no
affected rows.

Introducing a specialized exception allows for callers to more easily
silence, log, or turn them update failures into user facing exceptions
(e.g. 404s).

Thanks Mariusz for the review.

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/update_only_fields/tests.py b/tests/update_only_fields/tests.py
index 2c86995799..9595c767eb 100644
--- a/tests/update_only_fields/tests.py
+++ b/tests/update_only_fields/tests.py
@@ -1,3 +1,5 @@
+from django.core.exceptions import ObjectNotUpdated
+from django.db import DatabaseError, transaction
 from django.db.models.signals import post_save, pre_save
 from django.test import TestCase
 
@@ -292,3 +294,17 @@ class UpdateOnlyFieldsTests(TestCase):
         employee_boss = Employee.objects.create(name="Boss", gender="F")
         with self.assertRaisesMessage(ValueError, self.msg % "id"):
             employee_boss.save(update_fields=["id"])
+
+    def test_update_fields_not_updated(self):
+        obj = Person.objects.create(name="Sara", gender="F")
+        Person.objects.filter(pk=obj.pk).delete()
+        msg = "Save with update_fields did not affect any rows."
+        # Make sure backward compatibility with DatabaseError is preserved.
+        exceptions = [DatabaseError, ObjectNotUpdated, Person.NotUpdated]
+        for exception in exceptions:
+            with (
+                self.subTest(exception),
+                self.assertRaisesMessage(DatabaseError, msg),
+                transaction.atomic(),
+            ):
+                obj.save(update_fields=["name"])