Fix tagged page page copy regression in _copy_m2m_relations (#7224)

Fixes #7230

CHANGELOG.txt

@@ -17,6 +17,7 @@ Changelog
  * Fix: Prevent “Forgotten password” link from overlapping with field on mobile devices (Helen Chapman)
  * Fix: Snippet admin urls are now namespaced to avoid ambiguity with the primary key component of the url (Matt Westcott)
  * Fix: Save order of promoted search results (Hardcodd)
+ * Fix: Prevent error on copying pages with ClusterTaggableManager relations and multi-level inheritance (Chris Pollard)
 
 
 2.13.1 (01.06.2021)

CONTRIBUTORS.rst

@@ -516,6 +516,7 @@ Contributors
 * Tidjani Dia
 * Jan Seifert
 * hardcodd
+* Chris Pollard
 
 Translators
 ===========

docs/releases/2.14.rst

@@ -28,6 +28,7 @@ Bug fixes
  * The Wagtail admin urls will now respect the ``APPEND_SLASH`` setting (Tidjani Dia)
  * Prevent “Forgotten password” link from overlapping with field on mobile devices (Helen Chapman)
  * Snippet admin urls are now namespaced to avoid ambiguity with the primary key component of the url (Matt Westcott)
+ * Prevent error on copying pages with ClusterTaggableManager relations and multi-level inheritance (Chris Pollard)
 
 Upgrade considerations
 ======================

wagtail/core/models.py

@@ -124,7 +124,7 @@ def _copy_m2m_relations(source, target, exclude_fields=None, update_attrs=None):
         if field.many_to_many and field.name not in exclude_fields and not field.auto_created and not isinstance(field, ParentalManyToManyField):
             try:
                 # Do not copy m2m links with a through model that has a ParentalKey to the model being copied - these will be copied as child objects
-                through_model_parental_links = [field for field in field.through._meta.get_fields() if isinstance(field, ParentalKey) and (field.related_model == source.__class__ or field.related_model in source._meta.parents)]
+                through_model_parental_links = [field for field in field.through._meta.get_fields() if isinstance(field, ParentalKey) and issubclass(source.__class__, field.related_model)]
                 if through_model_parental_links:
                     continue
             except AttributeError:

wagtail/core/tests/test_page_model.py

@@ -28,7 +28,7 @@ from wagtail.tests.testapp.models import (
     CustomPageQuerySet, EventCategory, EventIndex, EventPage, EventPageSpeaker, GenericSnippetPage,
     ManyToManyBlogPage, MTIBasePage, MTIChildPage, MyCustomPage, OneToOnePage,
     PageWithExcludedCopyField, SimpleChildPage, SimplePage, SimpleParentPage, SingleEventPage,
-    SingletonPage, StandardIndex, StreamPage, TaggedPage)
+    SingletonPage, StandardIndex, StreamPage, TaggedGrandchildPage, TaggedPage)
 from wagtail.tests.utils import WagtailTestUtils
 
 
@@ -1534,6 +1534,36 @@ class TestCopyPage(TestCase):
             for item_id in new_tagged_item_ids
         ]))
 
+    def test_copy_subclassed_page_copies_tags(self):
+        # create and publish a TaggedGrandchildPage under Events
+        event_index = Page.objects.get(url_path='/home/events/')
+        sub_tagged_page = TaggedGrandchildPage(title='My very special tagged page', slug='my-special-tagged-page')
+        sub_tagged_page.tags.add('wagtail', 'bird')
+        event_index.add_child(instance=sub_tagged_page)
+        sub_tagged_page.save_revision().publish()
+
+        old_tagged_item_ids = [item.id for item in sub_tagged_page.tagged_items.all()]
+        # there should be two items here, with defined (truthy) IDs
+        self.assertEqual(len(old_tagged_item_ids), 2)
+        self.assertTrue(all(old_tagged_item_ids))
+
+        # copy to underneath homepage
+        homepage = Page.objects.get(url_path='/home/')
+        new_sub_tagged_page = sub_tagged_page.copy(to=homepage)
+
+        self.assertNotEqual(sub_tagged_page.id, new_sub_tagged_page.id)
+
+        # new page should also have two tags
+        new_tagged_item_ids = [item.id for item in new_sub_tagged_page.tagged_items.all()]
+        self.assertEqual(len(new_tagged_item_ids), 2)
+        self.assertTrue(all(new_tagged_item_ids))
+
+        # new tagged_item IDs should differ from old ones
+        self.assertTrue(all([
+            item_id not in old_tagged_item_ids
+            for item_id in new_tagged_item_ids
+        ]))
+
     def test_copy_page_with_m2m_relations(self):
         # create and publish a ManyToManyBlogPage under Events
         event_index = Page.objects.get(url_path='/home/events/')

wagtail/tests/testapp/migrations/0060_taggedchildpage_taggedgrandchildpage.py

@@ -0,0 +1,34 @@
+# Generated by Django 3.2.3 on 2021-05-28 21:21
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tests', '0059_deadlystreampage'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='TaggedChildPage',
+            fields=[
+                ('taggedpage_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='tests.taggedpage')),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('tests.taggedpage',),
+        ),
+        migrations.CreateModel(
+            name='TaggedGrandchildPage',
+            fields=[
+                ('taggedchildpage_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='tests.taggedchildpage')),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('tests.taggedchildpage',),
+        ),
+    ]

wagtail/tests/testapp/models.py

@@ -889,6 +889,14 @@ class TaggedPage(Page):
     ]
 
 
+class TaggedChildPage(TaggedPage):
+    pass
+
+
+class TaggedGrandchildPage(TaggedChildPage):
+    pass
+
+
 class SingletonPage(Page):
     @classmethod
     def can_create_at(cls, parent):