Fixed problem when setting django.db.models.functions.Now() in DateTimeField (#635)

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Next Release
 
+#### Fixes
+
+- Fixed 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)
 
 #### Fixes

auditlog/diff.py

@@ -66,7 +66,11 @@ def get_field_value(obj, field):
         if isinstance(field, DateTimeField):
             # DateTimeFields are timezone-aware, so we need to convert the field
             # to its naive form before we can accurately compare them for changes.
-            value = field.to_python(getattr(obj, field.name, None))
+            value = getattr(obj, field.name, None)
+            try:
+                value = field.to_python(value)
+            except TypeError:
+                return value
             if (
                 value is not None
                 and settings.USE_TZ

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.functions import Now
 from django.db.models.signals import pre_save
 from django.test import RequestFactory, TestCase, override_settings
 from django.urls import resolve, reverse
@@ -1061,6 +1062,24 @@ class DateTimeFieldModelTest(TestCase):
         )
         dtm.save()
 
+    def test_datetime_field_functions_now(self):
+        timestamp = datetime.datetime(2017, 1, 10, 15, 0, tzinfo=timezone.utc)
+        date = datetime.date(2017, 1, 10)
+        time = datetime.time(12, 0)
+
+        dtm = DateTimeFieldModel(
+            label="DateTimeField model",
+            timestamp=timestamp,
+            date=date,
+            time=time,
+            naive_dt=Now(),
+        )
+        dtm.save()
+        dtm.naive_dt = Now()
+        self.assertEqual(dtm.naive_dt, Now())
+        dtm.save()
+        self.assertEqual(dtm.naive_dt, Now())
+
 
 class UnregisterTest(TestCase):
     def setUp(self):