Update Page.copy_for_translation to create parents as aliases

wagtail/core/models.py

@@ -2082,7 +2082,7 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
     create_alias.alters_data = True
 
     @transaction.atomic
-    def copy_for_translation(self, locale, copy_parents=False, exclude_fields=None):
+    def copy_for_translation(self, locale, copy_parents=False, alias=False, exclude_fields=None):
         """
         Copies this page for the specified locale.
         """
@@ -2098,7 +2098,7 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
                     raise ParentNotTranslatedError
 
                 translated_parent = parent.copy_for_translation(
-                    locale, copy_parents=True
+                    locale, copy_parents=True, alias=True
                 )
         else:
             # Don't duplicate the root page for translation. Create new locale as a sibling
@@ -2111,6 +2111,15 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
         # Find available slug for new page
         slug = find_available_slug(translated_parent, slug)
 
+        if alias:
+            return self.create_alias(
+                parent=translated_parent,
+                update_slug=slug,
+                update_locale=locale,
+                reset_translation_key=False,
+            )
+
+        else:
             # Update locale on translatable child objects as well
             def process_child_object(
                 original_page, page_copy, child_relation, child_object

wagtail/core/tests/test_page_model.py

@@ -2010,6 +2010,17 @@ class TestCopyForTranslation(TestCase):
         # self.assertEqual(ffr_award.translation_key, en_award.translation_key)
         # self.assertEqual(list(fr_award.get_translations()), [en_award])
 
+    def test_copies_missing_parents_as_aliases(self):
+        fr_eventpage = self.en_eventpage.copy_for_translation(self.fr_locale, copy_parents=True)
+        fr_eventindex = fr_eventpage.get_parent()
+
+        # Check parent is a translation of its English original
+        self.assertEqual(fr_eventindex.locale, self.fr_locale)
+        self.assertEqual(fr_eventindex.translation_key, self.en_eventindex.translation_key)
+
+        # Check parent is also an alias of its English original
+        self.assertEqual(fr_eventindex.alias_of, self.en_eventindex)
+
 
 class TestSubpageTypeBusinessRules(TestCase, WagtailTestUtils):
     def test_allowed_subpage_models(self):