Fix FormSubmissionsPanel on Django 5.0 when creating a new form page

Fixes #11405

Django 5.0 rejects `FormSubmission.objects.filter(page=page)` when `page` is an unsaved in-memory instance. Since these can clearly not have any submissions, return an empty queryset in this case.

Also add end-to-end tests for the create and edit views with FormSubmissionsPanel in place.

wagtail/contrib/forms/panels.py

@@ -18,7 +18,11 @@ class FormSubmissionsPanel(Panel):
         def submissions(self):
             form_page_model = self.panel.model
             form_submissions_model = form_page_model().get_submission_class()
-            return form_submissions_model.objects.filter(page=self.instance)
+            if self.instance.pk:
+                return form_submissions_model.objects.filter(page=self.instance)
+            else:
+                # Page has not been created yet, so there can't be any submissions
+                return form_submissions_model.objects.none()
 
         @cached_property
         def submission_count(self):

wagtail/contrib/forms/tests/test_views.py

@@ -76,6 +76,30 @@ class TestFormResponsesPanel(TestCase):
         self.assertFalse(self.panel.is_shown())
 
 
+class TestFormResponsesPanelWithNewPage(TestCase):
+    def setUp(self):
+        self.request = RequestFactory().get("/")
+        user = AnonymousUser()  # technically, Anonymous users cannot access the admin
+        self.request.user = user
+
+        self.form_page = FormPage()
+
+        self.FormPageForm = get_form_for_model(
+            FormPage,
+            form_class=WagtailAdminPageForm,
+            fields=["title", "slug", "to_address", "from_address", "subject"],
+        )
+
+        panel = FormSubmissionsPanel().bind_to_model(FormPage)
+        self.panel = panel.get_bound_panel(
+            instance=self.form_page, form=self.FormPageForm(), request=self.request
+        )
+
+    def test_render_without_submissions(self):
+        """The panel should not be shown if the number of submission is zero."""
+        self.assertFalse(self.panel.is_shown())
+
+
 class TestFormResponsesPanelWithCustomSubmissionClass(WagtailTestUtils, TestCase):
     def setUp(self):
         self.request = RequestFactory().get("/")
@@ -1824,3 +1848,85 @@ class TestPreview(WagtailTestUtils, TestCase):
                 response = self.client.get(preview_url + params)
                 self.assertEqual(response.status_code, 200)
                 self.assertTemplateUsed(response, template)
+
+
+class TestFormPageCreate(WagtailTestUtils, TestCase):
+    def setUp(self):
+        # Find root page
+        self.root_page = Page.objects.get(id=2)
+
+        # Login
+        self.user = self.login()
+
+    def test_get_creation_form(self):
+        response = self.client.get(
+            reverse(
+                "wagtailadmin_pages:add",
+                args=("tests", "formpage", self.root_page.id),
+            )
+        )
+        self.assertEqual(response.status_code, 200)
+
+    def test_post_creation_form(self):
+        post_data = {
+            "title": "Form page!",
+            "slug": "contact-us",
+            "form_fields-TOTAL_FORMS": "1",
+            "form_fields-INITIAL_FORMS": "1",
+            "form_fields-MIN_NUM_FORMS": "0",
+            "form_fields-MAX_NUM_FORMS": "1000",
+            "form_fields-0-id": "",
+            "form_fields-0-label": "Field One",
+            "form_fields-0-field_type": "singleline",
+        }
+        response = self.client.post(
+            reverse(
+                "wagtailadmin_pages:add",
+                args=("tests", "formpage", self.root_page.id),
+            ),
+            post_data,
+        )
+        # Find the page and check it
+        page = Page.objects.get(slug="contact-us")
+
+        # Should be redirected to edit page
+        self.assertRedirects(
+            response, reverse("wagtailadmin_pages:edit", args=(page.id,))
+        )
+
+
+class TestFormPageEdit(WagtailTestUtils, TestCase):
+    def setUp(self):
+        self.form_page = make_form_page()
+
+        # Login
+        self.user = self.login()
+
+    def test_get_edit_form(self):
+        response = self.client.get(
+            reverse("wagtailadmin_pages:edit", args=(self.form_page.id,))
+        )
+        self.assertEqual(response.status_code, 200)
+
+    def test_post_edit_form(self):
+        post_data = {
+            "title": "Updated form page",
+            "slug": "contact-us",
+            "form_fields-TOTAL_FORMS": "1",
+            "form_fields-INITIAL_FORMS": "1",
+            "form_fields-MIN_NUM_FORMS": "0",
+            "form_fields-MAX_NUM_FORMS": "1000",
+            "form_fields-0-id": "",
+            "form_fields-0-label": "Field One",
+            "form_fields-0-field_type": "singleline",
+        }
+        response = self.client.post(
+            reverse("wagtailadmin_pages:edit", args=(self.form_page.id,)),
+            post_data,
+        )
+        # Should be redirected to edit page
+        self.assertRedirects(
+            response, reverse("wagtailadmin_pages:edit", args=(self.form_page.id,))
+        )
+        page = Page.objects.get(slug="contact-us").get_latest_revision_as_object()
+        self.assertEqual(page.title, "Updated form page")

wagtail/test/testapp/models.py

@@ -49,6 +49,7 @@ from wagtail.contrib.forms.models import (
     AbstractFormField,
     AbstractFormSubmission,
 )
+from wagtail.contrib.forms.panels import FormSubmissionsPanel
 from wagtail.contrib.forms.views import SubmissionsListView
 from wagtail.contrib.settings.models import (
     BaseGenericSetting,
@@ -568,6 +569,7 @@ class FormPage(AbstractEmailForm):
             ],
             "Email",
         ),
+        FormSubmissionsPanel(),
     ]