Fix: skip objects using placeholders without source (#253)

* Skip objects using placeholders without source

* test: add usage view test for alias saved to clipboard

djangocms_alias/models.py

@@ -133,6 +133,11 @@ def objects_using(self):
         plugins = self.cms_plugins.select_related("placeholder").prefetch_related("placeholder__source")
         for plugin in plugins:
             obj = plugin.placeholder.source
+
+            # Skip plugins that have no placeholder source e.g clipboard
+            if obj is None:
+                continue
+
             obj_class_name = obj.__class__.__name__
             if obj_class_name.endswith("Content"):
                 attr_name = obj_class_name.replace("Content", "").lower()

tests/test_views.py

@@ -1580,3 +1580,24 @@ def test_view_multilanguage(self):
         self.assertNotContains(list_response, alias_content_de.name)
         self.assertNotContains(detail_response, en_plugin.body)
         self.assertNotContains(list_response, alias.name)
+
+    def test_usage_view_if_alias_is_saved_to_clipboard(self):
+        """
+        The usage view should ignore the clipboard entry
+        """
+
+        alias = self._create_alias()
+        placeholder = Placeholder.objects.create(slot="clipboard")
+        add_plugin(placeholder, "Alias", language="en", alias=alias)
+
+        with self.login_user_context(self.superuser):
+            response = self.client.get(
+                admin_reverse(
+                    USAGE_ALIAS_URL_NAME,
+                    args=[alias.pk],
+                ),
+            )
+
+            self.assertEqual(response.status_code, 200)
+            # Check that the alias is displayed in the response content
+            self.assertContains(response, alias.name)