Call 'specific' attribute when fetching page

Get the specific implementation of a page, this shows the correct
get_admin_display_title on the delete confirmation page.

CHANGELOG.txt

@@ -23,6 +23,7 @@ Changelog
  * Fix: Correct dropdown arrow styling in Firefox, IE11 (Janneke Janssen, Alexs Mathilda)
  * Fix: Password reset no indicates specific validation errors on certain password restrictions (Lucas Moeskops)
  * Fix: Fix a typo within documentation for pages (DanAtShenTech)
+ * Fix: Confirmation page on page deletion now respects custom `get_admin_display_title` methods (Kim Chee Leong)
 
 
 2.0.1 (xx.xx.xxxx) - IN DEVELOPMENT

docs/releases/2.1.rst

@@ -37,6 +37,7 @@ Bug fixes
  * Correct dropdown arrow styling in Firefox, IE11 (Janneke Janssen, Alexs Mathilda)
  * Password reset no indicates specific validation errors on certain password restrictions (Lucas Moeskops)
  * Fix a typo within documentation for pages (DanAtShenTech)
+ * Confirmation page on page deletion now respects custom ``get_admin_display_title`` methods (Kim Chee Leong)
 
 
 Upgrade considerations

wagtail/admin/tests/test_pages_views.py

@@ -2033,6 +2033,13 @@ class TestPageDelete(TestCase, WagtailTestUtils):
         # deletion should not actually happen on GET
         self.assertTrue(SimplePage.objects.filter(id=self.child_page.id).exists())
 
+    def test_page_delete_specific_admin_title(self):
+        response = self.client.get(reverse('wagtailadmin_pages:delete', args=(self.child_page.id, )))
+        self.assertEqual(response.status_code, 200)
+
+        # The admin_display_title specific to ChildPage is shown on the delete confirmation page.
+        self.assertContains(response, self.child_page.get_admin_display_title())
+
     def test_page_delete_bad_permissions(self):
         # Remove privileges from user
         self.user.is_superuser = False

wagtail/admin/views/pages.py

@@ -517,7 +517,7 @@ def edit(request, page_id):
 
 
 def delete(request, page_id):
-    page = get_object_or_404(Page, id=page_id)
+    page = get_object_or_404(Page, id=page_id).specific
     if not page.permissions_for_user(request.user).can_delete():
         raise PermissionDenied
 

wagtail/tests/testapp/models.py

@@ -141,6 +141,9 @@ class SimplePage(Page):
         FieldPanel('content'),
     ]
 
+    def get_admin_display_title(self):
+        return "%s (simple page)" % super().get_admin_display_title()
+
 
 # Page with Excluded Fields when copied
 class PageWithExcludedCopyField(Page):