Fixes #3780: Fix AttributeError exception in API docs

netbox/extras/api/customfields.py

@@ -124,6 +124,9 @@ class CustomFieldModelSerializer(ValidatedModelSerializer):
 
         else:
 
+            if not hasattr(self, 'initial_data'):
+                self.initial_data = {}
+
             # Populate default values
             if fields and 'custom_fields' not in self.initial_data:
                 self.initial_data['custom_fields'] = {}

netbox/utilities/tests/test_api.py

@@ -1,7 +1,13 @@
+import urllib.parse
+
+from django.contrib.contenttypes.models import ContentType
+from django.test import Client, TestCase
 from django.urls import reverse
 from rest_framework import status
 
 from dcim.models import Region, Site
+from extras.constants import CF_TYPE_TEXT
+from extras.models import CustomField
 from ipam.models import VLAN
 from utilities.testing import APITestCase
 
@@ -117,3 +123,26 @@ class WritableNestedSerializerTest(APITestCase):
 
         self.assertHttpStatus(response, status.HTTP_400_BAD_REQUEST)
         self.assertEqual(VLAN.objects.count(), 0)
+
+
+class APIDocsTestCase(TestCase):
+
+    def setUp(self):
+        self.client = Client()
+
+        # Populate a CustomField to activate CustomFieldSerializer
+        content_type = ContentType.objects.get_for_model(Site)
+        self.cf_text = CustomField(type=CF_TYPE_TEXT, name='test')
+        self.cf_text.save()
+        self.cf_text.obj_type.set([content_type])
+        self.cf_text.save()
+
+    def test_api_docs(self):
+
+        url = reverse('api_docs')
+        params = {
+            "format": "openapi",
+        }
+
+        response = self.client.get('{}?{}'.format(url, urllib.parse.urlencode(params)))
+        self.assertEqual(response.status_code, 200)