Fix alias() not compatible with specific()

Fixes #11285

CHANGELOG.txt

@@ -34,6 +34,7 @@ Changelog
  * Fix: Avoid error when attempting to moderate a page drafted by a now deleted user (Dan Braghis)
  * Fix: Do not show multiple error messages when editing a Site to use existing hostname and port (Rohit Sharma)
  * Fix: Avoid error when exporting Aging Pages report where a page has an empty `last_published_by_user` (Chiemezuo Akujobi)
+ * Fix: Ensure Page querysets support using `alias` and `specific` (Tomasz Knapik)
  * Docs: Document, for contributors, the use of translate string literals passed as arguments to tags and filters using `_()` within templates (Chiemezuo Akujobi)
  * Docs: Document all features for the Documents app in one location (Neeraj Yetheendran)
  * Docs: Add section to testing docs about creating pages and working with page content (Mariana Bedran Lesche)

docs/releases/6.0.md

@@ -47,6 +47,7 @@ depth: 1
  * Avoid error when attempting to moderate a page drafted by a now deleted user (Dan Braghis)
  * Do not show multiple error messages when editing a Site to use existing hostname and port (Rohit Sharma)
  * Avoid error when exporting Aging Pages report where a page has an empty `last_published_by_user` (Chiemezuo Akujobi)
+ * Ensure Page querysets support using `alias` and `specific` (Tomasz Knapik)
 
 ### Documentation
 

wagtail/query.py

@@ -515,7 +515,7 @@ class SpecificIterable(BaseIterable):
         in the same order, with any annotations intact.
         """
         qs = self.queryset
-        annotation_aliases = qs.query.annotations.keys()
+        annotation_aliases = qs.query.annotation_select
         values_qs = qs.values("pk", "content_type", *annotation_aliases)
 
         # Gather items in batches to reduce peak memory usage

wagtail/tests/test_page_queryset.py

@@ -919,6 +919,25 @@ class TestSpecificQuery(WagtailTestUtils, TestCase):
         self.assertEqual(results.first().subscribers_count, 1)
         self.assertEqual(results.last().subscribers_count, 1)
 
+    def test_specific_query_with_alias(self):
+        """
+        Ensure alias() works with specific() queries.
+        See https://github.com/wagtail/wagtail/issues/11285 for more details
+        """
+
+        pages = Page.objects.live()
+        user = self.create_test_user()
+        pages.first().subscribers.create(user=user, comment_notifications=False)
+        pages.last().subscribers.create(user=user, comment_notifications=False)
+
+        # This would previously fail as described in #11285.
+        iter(
+            Page.objects.live()
+            .specific()
+            .alias(subscribers_count=Count("subscribers"))
+            .order_by("subscribers_count")
+        )
+
     def test_specific_gracefully_handles_missing_models(self):
         # 3567 - PageQuerySet.specific should gracefully handle pages whose class definition
         # is missing, by keeping them as basic Page instances.