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/models.py

@@ -269,6 +269,12 @@ class JSONModel(models.Model):
     history = AuditlogHistoryField(delete_related=False)
 
 
+class NullableJSONModel(models.Model):
+    json = models.JSONField(null=True, blank=True)
+
+    history = AuditlogHistoryField(delete_related=False)
+
+
 class SerializeThisModel(models.Model):
     label = models.CharField(max_length=24, unique=True)
     timestamp = models.DateTimeField()
@@ -346,6 +352,7 @@ auditlog.register(CharfieldTextfieldModel)
 auditlog.register(PostgresArrayFieldModel)
 auditlog.register(NoDeleteHistoryModel)
 auditlog.register(JSONModel)
+auditlog.register(NullableJSONModel)
 auditlog.register(
     SerializeThisModel,
     serialize_data=True,

auditlog_tests/tests.py

@@ -17,6 +17,7 @@ from django.contrib.auth.models import AnonymousUser, User
 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
@@ -46,6 +47,7 @@ from auditlog_tests.models import (
     ManyRelatedModel,
     ManyRelatedOtherModel,
     NoDeleteHistoryModel,
+    NullableJSONModel,
     PostgresArrayFieldModel,
     ProxyModel,
     RelatedModel,
@@ -1090,6 +1092,14 @@ class DateTimeFieldModelTest(TestCase):
         dtm.save()
         self.assertEqual(dtm.naive_dt, Now())
 
+    def test_json_field_value_none(self):
+        json_model = NullableJSONModel(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):
@@ -1196,7 +1206,7 @@ class RegisterModelSettingsTest(TestCase):
 
         self.assertTrue(self.test_auditlog.contains(SimpleExcludeModel))
         self.assertTrue(self.test_auditlog.contains(ChoicesFieldModel))
-        self.assertEqual(len(self.test_auditlog.get_models()), 25)
+        self.assertEqual(len(self.test_auditlog.get_models()), 26)
 
     def test_register_models_register_model_with_attrs(self):
         self.test_auditlog._register_models(