Fixes #11109: Fix nullification of custom object & multi-object fields via REST API

docs/release-notes/version-3.3.md

@@ -18,6 +18,7 @@
 * [#11077](https://github.com/netbox-community/netbox/issues/11077) - Honor configured date format when displaying date custom field values in tables
 * [#11087](https://github.com/netbox-community/netbox/issues/11087) - Fix background color of bottom banner content
 * [#11101](https://github.com/netbox-community/netbox/issues/11101) - Correct circuits count under site view
+* [#11109](https://github.com/netbox-community/netbox/issues/11109) - Fix nullification of custom object & multi-object fields via REST API
 * [#11128](https://github.com/netbox-community/netbox/issues/11128) - Disable ordering changelog table by object to avoid exception
 * [#11142](https://github.com/netbox-community/netbox/issues/11142) - Correct available choices for status under IP range filter form
 * [#11168](https://github.com/netbox-community/netbox/issues/11168) - Honor `RQ_DEFAULT_TIMEOUT` config parameter when using Redis Sentinel

netbox/extras/api/customfields.py

@@ -72,7 +72,7 @@ class CustomFieldsDataField(Field):
 
         # Serialize object and multi-object values
         for cf in self._get_custom_fields():
-            if cf.name in data and cf.type in (
+            if cf.name in data and data[cf.name] not in (None, []) and cf.type in (
                     CustomFieldTypeChoices.TYPE_OBJECT,
                     CustomFieldTypeChoices.TYPE_MULTIOBJECT
             ):

netbox/extras/tests/test_customfields.py

@@ -854,6 +854,18 @@ class CustomFieldAPITest(APITestCase):
             [vlans[1].pk, vlans[2].pk]
         )
 
+        # Clear related objects
+        data = {
+            'custom_fields': {
+                'object_field': None,
+                'multiobject_field': [],
+            },
+        }
+        response = self.client.patch(url, data, format='json', **self.header)
+        self.assertHttpStatus(response, status.HTTP_200_OK)
+        self.assertIsNone(response.data['custom_fields']['object_field'])
+        self.assertListEqual(response.data['custom_fields']['multiobject_field'], [])
+
     def test_minimum_maximum_values_validation(self):
         site2 = Site.objects.get(name='Site 2')
         url = reverse('dcim-api:site-detail', kwargs={'pk': site2.pk})