Fixed a problem when setting Value(None) in JSONField

CHANGELOG.md

@@ -4,7 +4,8 @@
 
 #### Fixes
 
-- Fixed problem when setting `django.db.models.functions.Now()` in `DateTimeField` ([#635](https://github.com/jazzband/django-auditlog/pull/635))
+- Fixed a problem when setting `Value(None)` in `JSONField` ([#646](https://github.com/jazzband/django-auditlog/pull/646))
+- Fixed a problem when setting `django.db.models.functions.Now()` in `DateTimeField` ([#635](https://github.com/jazzband/django-auditlog/pull/635))
 
 ## 3.0.0 (2024-04-12)
 

auditlog/diff.py

@@ -79,7 +79,10 @@ def get_field_value(obj, field):
                 value = django_timezone.make_naive(value, timezone=timezone.utc)
         elif isinstance(field, JSONField):
             value = field.to_python(getattr(obj, field.name, None))
-            value = json.dumps(value, sort_keys=True, cls=field.encoder)
+            try:
+                value = json.dumps(value, sort_keys=True, cls=field.encoder)
+            except TypeError:
+                pass
         elif (field.one_to_one or field.many_to_one) and hasattr(field, "rel_class"):
             value = smart_str(
                 getattr(obj, field.get_attname(), None), strings_only=True

auditlog_tests/tests.py

@@ -17,6 +17,7 @@
 from django.contrib.contenttypes.models import ContentType
 from django.core import management
 from django.db import models
+from django.db.models import JSONField, Value
 from django.db.models.functions import Now
 from django.db.models.signals import pre_save
 from django.test import RequestFactory, TestCase, override_settings
@@ -1090,6 +1091,14 @@ def test_datetime_field_functions_now(self):
         dtm.save()
         self.assertEqual(dtm.naive_dt, Now())
 
+    def test_json_field_value_none(self):
+        json_model = JSONModel(json=Value(None, JSONField()))
+        json_model.save()
+        self.assertEqual(json_model.history.count(), 1)
+        self.assertEqual(
+            json_model.history.latest().changes_dict["json"][1], 'Value(None)'
+        )
+
 
 class UnregisterTest(TestCase):
     def setUp(self):