feat(monitor): Change default to None when the field is marked as nullable and no default is provided (#599)

CHANGES.rst

@@ -3,6 +3,8 @@ Changelog
 
 To be released
 --------------
+- Remove MonitorField deprecation warning. `None` - instead of
+  `django.utils.timezone.now` will be used when nullable and no default provided (GH-#599)
 - Add deprecation warning for MonitorField. The default value will be `None`
   instead of `django.utils.timezone.now` - when nullable and without a default.
 - Add Brazilian Portuguese translation (GH-#578)

model_utils/fields.py

@@ -1,6 +1,5 @@
 import secrets
 import uuid
-import warnings
 
 from django.conf import settings
 from django.core.exceptions import ValidationError
@@ -107,17 +106,8 @@ class MonitorField(models.DateTimeField):
     """
 
     def __init__(self, *args, monitor, when=None, **kwargs):
-        if kwargs.get("null") and kwargs.get("default") is None:
-            warning_message = (
-                "{}.default is set to 'django.utils.timezone.now' - when nullable"
-                " and no default. This behavior will be deprecated in the next"
-                " major release in favor of 'None'. See"
-                " https://django-model-utils.readthedocs.io/en/stable/fields.html"
-                "#monitorfield for more information."
-            ).format(self.__class__.__name__)
-            warnings.warn(warning_message, DeprecationWarning)
-
-        kwargs.setdefault('default', now)
+        default = None if kwargs.get("null") else now
+        kwargs.setdefault('default', default)
         self.monitor = monitor
         if when is not None:
             when = set(when)

tests/models.py

@@ -98,6 +98,7 @@ class TimeFrameManagerAdded(TimeFramedModel):
 class Monitored(models.Model):
     name = models.CharField(max_length=25)
     name_changed = MonitorField(monitor="name")
+    name_changed_nullable = MonitorField(monitor="name", null=True)
 
 
 class MonitorWhen(models.Model):

tests/test_fields/test_monitor_field.py

@@ -34,17 +34,15 @@ class MonitorFieldTests(TestCase):
         with self.assertRaises(TypeError):
             MonitorField()
 
-    def test_nullable_without_default_deprecation(self):
-        warning_message = (
-            "{}.default is set to 'django.utils.timezone.now' - when nullable"
-            " and no default. This behavior will be deprecated in the next"
-            " major release in favor of 'None'. See"
-            " https://django-model-utils.readthedocs.io/en/stable/fields.html"
-            "#monitorfield for more information."
-        ).format(MonitorField.__name__)
+    def test_monitor_default_is_none_when_nullable(self):
+        self.assertIsNone(self.instance.name_changed_nullable)
+        expected_datetime = datetime(2022, 1, 18, 12, 0, 0, tzinfo=timezone.utc)
 
-        with self.assertWarns(DeprecationWarning, msg=warning_message):
-            MonitorField(monitor="foo", null=True, default=None)
+        self.instance.name = "Jose"
+        with time_machine.travel(expected_datetime, tick=False):
+            self.instance.save()
+
+        self.assertEqual(self.instance.name_changed_nullable, expected_datetime)
 
 
 class MonitorWhenFieldTests(TestCase):