Add missing bind_to(instance) to ModelAdmin edit view

Fixes #6413. Following the refactor in 80cc70b7ce this was not being called - this is necessary to propagate the instance down nested edit handlers.

wagtail/contrib/modeladmin/tests/test_simple_modeladmin.py

@@ -8,9 +8,10 @@ from openpyxl import load_workbook
 
 from wagtail.admin.edit_handlers import FieldPanel, TabbedInterface
 from wagtail.contrib.modeladmin.helpers.search import DjangoORMSearchHandler
+from wagtail.core.models import Page
 from wagtail.images.models import Image
 from wagtail.images.tests.utils import get_test_image_file
-from wagtail.tests.modeladmintest.models import Author, Book, Publisher, Token
+from wagtail.tests.modeladmintest.models import Author, Book, Publisher, RelatedLink, Token
 from wagtail.tests.modeladmintest.wagtail_hooks import BookModelAdmin
 from wagtail.tests.utils import WagtailTestUtils
 
@@ -272,6 +273,21 @@ class TestCreateView(TestCase, WagtailTestUtils):
 
             mock_form_clean.assert_called_once()
 
+    def test_create_view_with_multifieldpanel(self):
+        # https://github.com/wagtail/wagtail/issues/6413
+        response = self.client.get('/admin/modeladmintest/relatedlink/create/')
+        self.assertEqual(response.status_code, 200)
+
+        response = self.client.post('/admin/modeladmintest/relatedlink/create/', {
+            'title': "Homepage",
+            'link': Page.objects.filter(depth=2).first().id,
+        })
+        # Should redirect back to index
+        self.assertRedirects(response, '/admin/modeladmintest/relatedlink/')
+
+        # Check that the link was created
+        self.assertEqual(RelatedLink.objects.filter(title="Homepage").count(), 1)
+
 
 class TestInspectView(TestCase, WagtailTestUtils):
     fixtures = ['modeladmintest_test.json']
@@ -409,6 +425,22 @@ class TestEditView(TestCase, WagtailTestUtils):
 
             mock_form_clean.assert_called_once()
 
+    def test_edit_view_with_multifieldpanel(self):
+        # https://github.com/wagtail/wagtail/issues/6413
+        link = RelatedLink.objects.create(title='Homepage', link=Page.objects.filter(depth=2).first())
+        response = self.client.get('/admin/modeladmintest/relatedlink/edit/%d/' % link.id)
+        self.assertEqual(response.status_code, 200)
+
+        response = self.client.post('/admin/modeladmintest/relatedlink/edit/%d/' % link.id, {
+            'title': "Homepage edited",
+            'link': Page.objects.filter(depth=2).first().id,
+        })
+        # Should redirect back to index
+        self.assertRedirects(response, '/admin/modeladmintest/relatedlink/')
+
+        # Check that the link was updated
+        self.assertEqual(RelatedLink.objects.filter(title="Homepage edited").count(), 1)
+
 
 class TestPageSpecificViews(TestCase, WagtailTestUtils):
     fixtures = ['modeladmintest_test.json']

wagtail/contrib/modeladmin/views.py

@@ -118,10 +118,13 @@ class ModelFormView(WMABaseView, FormView):
         return form
 
     def get_edit_handler(self):
+        instance = self.get_instance()
         edit_handler = self.model_admin.get_edit_handler(
-            instance=self.get_instance(), request=self.request
+            instance=instance, request=self.request
+        )
+        return edit_handler.bind_to(
+            model=self.model_admin.model, request=self.request, instance=instance
         )
-        return edit_handler.bind_to(model=self.model_admin.model, request=self.request)
 
     def get_form_class(self):
         return self.edit_handler.get_form_class()

wagtail/tests/modeladmintest/migrations/0009_relatedlink.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.1.1 on 2020-10-01 18:16
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('wagtailcore', '0057_page_locale_fields_notnull'),
+        ('modeladmintest', '0008_solobook'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='RelatedLink',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('title', models.CharField(max_length=255)),
+                ('link', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='+', to='wagtailcore.page')),
+            ],
+        ),
+    ]

wagtail/tests/modeladmintest/models.py

@@ -1,6 +1,8 @@
 from django.db import models
 
-from wagtail.admin.edit_handlers import FieldPanel, ObjectList, TabbedInterface
+from wagtail.admin.edit_handlers import (
+    FieldPanel, MultiFieldPanel, ObjectList, PageChooserPanel, TabbedInterface
+)
 from wagtail.core.models import Page
 from wagtail.search import index
 
@@ -124,3 +126,24 @@ class Friend(models.Model):
 
     def __str__(self):
         return self.first_name
+
+
+class RelatedLink(models.Model):
+    title = models.CharField(
+        max_length=255,
+    )
+    link = models.ForeignKey(
+        Page,
+        on_delete=models.CASCADE,
+        related_name='+'
+    )
+
+    panels = [
+        MultiFieldPanel(
+            [
+                FieldPanel('title'),
+                PageChooserPanel('link'),
+            ],
+            heading='Related Link'
+        ),
+    ]

wagtail/tests/modeladmintest/wagtail_hooks.py

@@ -6,7 +6,9 @@ from wagtail.contrib.modeladmin.views import CreateView, EditView, IndexView
 from wagtail.tests.testapp.models import BusinessChild, EventPage, SingleEventPage
 
 from .forms import PublisherModelAdminForm
-from .models import Author, Book, Contributor, Friend, Person, Publisher, Token, VenuePage, Visitor
+from .models import (
+    Author, Book, Contributor, Friend, Person, Publisher, RelatedLink, Token, VenuePage, Visitor
+)
 
 
 class AuthorModelAdmin(ModelAdmin):
@@ -164,6 +166,11 @@ class BusinessChildAdmin(ModelAdmin):
     menu_label = "BusinessSprog"
 
 
+class RelatedLinkAdmin(ModelAdmin):
+    model = RelatedLink
+    menu_label = "Related Links"
+
+
 modeladmin_register(AuthorModelAdmin)
 modeladmin_register(BookModelAdmin)
 modeladmin_register(TokenModelAdmin)
@@ -174,3 +181,4 @@ modeladmin_register(PersonAdmin)
 modeladmin_register(FriendAdmin)
 modeladmin_register(VisitorAdmin)
 modeladmin_register(ContributorAdmin)
+modeladmin_register(RelatedLinkAdmin)