Value(None, output_field=JSONField()) incorrectly saves as SQL NULL in bulk_update()

[Clifford Gama]

When using bulk_update() with a Value(None, output_field=JSONField()) expression, the value is incorrectly saved as a SQL NULL rather than a JSON null. This behavior was temporarily fixed in 00c690efbc0b10f67924687f24a7b30397bf47d9 due to incomplete for_save propagation during expression resolution (bug in #36419), but reappears after the proper restoration of for_save handling in #36419.

tests/queries/test_bulk_update.py

@@ -3 +3 @@
 
 from django.core.exceptions import FieldDoesNotExist
 from django.db import connection
-from django.db.models import F
+from django.db.models import F, Value, JSONField
 from django.db.models.functions import Coalesce, Lower
 from django.db.utils import IntegrityError
 from django.test import TestCase, override_settings, skipUnlessDBFeature
@@ -315 +315 @@
                 sql_null_qs = JSONFieldNullable.objects.filter(json_field__isnull=True)
                 self.assertSequenceEqual(sql_null_qs, [obj])
 
+    @skipUnlessDBFeature("supports_json_field")
+    def test_json_field_json_null_value(self):
+        obj = JSONFieldNullable.objects.create(json_field={})
+        obj.json_field = Value(None, output_field=JSONField())
+        JSONFieldNullable.objects.bulk_update([obj], fields=["json_field"])
+        obj.refresh_from_db()
+        json_null_qs = JSONFieldNullable.objects.filter(json_field=None)
+        self.assertSequenceEqual(json_null_qs, [obj])
+
     def test_nullable_fk_after_related_save(self):
         parent = RelatedObject.objects.create()
         child = SingleObject()