[fix] Fixed target URL in "config_error" notification type

Bug:
The target_link callable was not returning the correct URL due to
changes in openwisp-notifications.

Fix:
Updated the target_link callable for "config_error" notification type
and improved test for better E2E testing.

Author: pandafy

openwisp_controller/config/tests/test_notifications.py

@@ -4,6 +4,7 @@
 from django.apps.registry import apps
 from django.conf import settings
 from django.test import TransactionTestCase
+from django.urls import reverse
 from requests.exceptions import RequestException
 from swapper import load_model
 
@@ -40,6 +41,7 @@ def setUp(self):
 
     def test_config_problem_notification(self):
         config = self._create_config()
+        device = config.device
         config.set_status_error()
 
         self.assertEqual(config.status, 'error')
@@ -53,8 +55,15 @@ def test_config_problem_notification(self):
             f'[example.com] ERROR: "{config.device}"'
             ' configuration encountered an error',
         )
-        self.assertIn('encountered an error', notification.message)
-        self.assertEqual(notification.target_url.endswith('#config-group'), True)
+        expected_target_url = ('https://example.com{}#config-group').format(
+            reverse(f'admin:{self.app_label}_device_change', args=[device.id])
+        )
+        self.assertEqual(
+            notification.message,
+            f'<p>The configuration of <a href="{expected_target_url}">{device.name}</a>'
+            ' has encountered an error. The last working configuration has been'
+            ' restored from a backup present on the filesystem of the device.</p>',
+        )
 
     def test_device_registered(self):
         # To avoid adding repetitive code for registering a device,

openwisp_controller/config/utils.py

@@ -203,5 +203,5 @@ def get_default_templates_queryset(
 
 
 def get_config_error_notification_target_url(obj, field, absolute_url=True):
-    url = _get_object_link(obj, field, absolute_url)
+    url = _get_object_link(obj._related_object(field), absolute_url)
     return f'{url}#config-group'