Add failing test for page model defined before wagtail.admin is loaded

wagtail/admin/tests/pages/test_create_page.py

@@ -1,4 +1,5 @@
 import datetime
+import unittest
 from unittest import mock
 
 from django.contrib.auth.models import Group, Permission
@@ -427,6 +428,27 @@ class TestPageCreation(WagtailTestUtils, TestCase):
         )
         self.assertRedirects(response, "/admin/")
 
+    @unittest.expectedFailure
+    def test_create_page_defined_before_admin_load(self):
+        """
+        Test that a page model defined before wagtail.admin is loaded has all fields present
+        """
+        response = self.client.get(
+            reverse(
+                "wagtailadmin_pages:add",
+                args=("earlypage", "earlypage", self.root_page.id),
+            )
+        )
+        self.assertEqual(response.status_code, 200)
+        self.assertTemplateUsed(response, "wagtailadmin/pages/create.html")
+        # Title field should be present and have TitleFieldPanel behaviour
+        # including syncing with slug
+        self.assertContains(response, 'data-w-sync-target-value="#id_slug"')
+        # SEO title should be present in promote tab
+        self.assertContains(
+            response, "The name of the page displayed on search engine results"
+        )
+
     def test_create_simplepage_post(self):
         post_data = {
             "title": "New page!",

wagtail/test/earlypage/migrations/0001_initial.py

@@ -0,0 +1,37 @@
+# Generated by Django 5.1.4 on 2025-01-03 15:30
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ("wagtailcore", "0094_alter_page_locale"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="EarlyPage",
+            fields=[
+                (
+                    "page_ptr",
+                    models.OneToOneField(
+                        auto_created=True,
+                        on_delete=django.db.models.deletion.CASCADE,
+                        parent_link=True,
+                        primary_key=True,
+                        serialize=False,
+                        to="wagtailcore.page",
+                    ),
+                ),
+                ("intro", models.TextField(blank=True)),
+            ],
+            options={
+                "abstract": False,
+            },
+            bases=("wagtailcore.page",),
+        ),
+    ]

wagtail/test/earlypage/models.py

@@ -0,0 +1,14 @@
+# This module DOES NOT import from wagtail.admin -
+# this tests that we are able to define Page models before wagtail.admin is loaded.
+
+from django.db import models
+
+from wagtail.models import Page
+
+
+class EarlyPage(Page):
+    intro = models.TextField(blank=True)
+
+    content_panels = Page.content_panels + [
+        "intro",
+    ]

wagtail/test/settings.py

@@ -135,6 +135,9 @@ MIDDLEWARE = (
 )
 
 INSTALLED_APPS = [
+    # Place wagtail.test.earlypage first, to test the behaviour of page models
+    # that are defined before wagtail.admin is loaded
+    "wagtail.test.earlypage",
     # Install wagtailredirects with its appconfig
     # There's nothing special about wagtailredirects, we just need to have one
     # app which uses AppConfigs to test that hooks load properly