Make title and slug optional in page previews

wagtail/admin/tests/pages/test_preview.py

@@ -173,7 +173,10 @@ class TestPreview(WagtailTestUtils, TestCase):
         )
         self.assertNotIn(preview_session_key, self.client.session)
 
-        response = self.client.post(preview_url, {**self.post_data, "title": ""})
+        response = self.client.post(
+            preview_url,
+            {**self.post_data, "date_from": "2025-02-31"},
+        )
 
         # Check the JSON response
         self.assertEqual(response.status_code, 200)
@@ -311,6 +314,51 @@ class TestPreview(WagtailTestUtils, TestCase):
         self.assertTemplateUsed(response, "tests/event_page.html")
         self.assertContains(response, "Bare minimum")
 
+    def test_preview_on_create_without_title_and_slug(self):
+        preview_url = reverse(
+            "wagtailadmin_pages:preview_on_add",
+            args=("tests", "eventpage", self.home_page.id),
+        )
+
+        preview_session_key = "wagtail-preview-tests-eventpage-{}".format(
+            self.home_page.id
+        )
+        self.assertNotIn(preview_session_key, self.client.session)
+
+        response = self.client.post(
+            preview_url,
+            {
+                "carousel_items-TOTAL_FORMS": 0,
+                "carousel_items-INITIAL_FORMS": 0,
+                "speakers-TOTAL_FORMS": 0,
+                "speakers-INITIAL_FORMS": 0,
+                "related_links-TOTAL_FORMS": 0,
+                "related_links-INITIAL_FORMS": 0,
+                "head_counts-TOTAL_FORMS": 0,
+                "head_counts-INITIAL_FORMS": 0,
+            },
+        )
+
+        # Check the JSON response
+        self.assertEqual(response.status_code, 200)
+        self.assertJSONEqual(
+            response.content.decode(),
+            {"is_valid": True, "is_available": True},
+        )
+
+        # Check the user can refresh the preview
+        preview_session_key = "wagtail-preview-tests-eventpage-{}".format(
+            self.home_page.id
+        )
+        self.assertIn(preview_session_key, self.client.session)
+
+        response = self.client.get(preview_url)
+
+        # Check the HTML response
+        self.assertEqual(response.status_code, 200)
+        self.assertTemplateUsed(response, "tests/event_page.html")
+        self.assertContains(response, "Placeholder title")
+
     def test_preview_on_edit_with_m2m_field(self):
         preview_url = reverse(
             "wagtailadmin_pages:preview_on_edit", args=(self.event_page.id,)
@@ -381,7 +429,10 @@ class TestPreview(WagtailTestUtils, TestCase):
         )
 
         # Send an invalid update request
-        response = self.client.post(preview_url, {**self.post_data, "title": ""})
+        response = self.client.post(
+            preview_url,
+            {**self.post_data, "date_to": "1234-56-78"},
+        )
         self.assertEqual(response.status_code, 200)
         self.assertJSONEqual(
             response.content.decode(),
@@ -440,6 +491,43 @@ class TestPreview(WagtailTestUtils, TestCase):
         self.assertTemplateUsed(response, "tests/event_page.html")
         self.assertContains(response, "Bare minimum")
 
+    def test_preview_on_edit_without_title_and_slug(self):
+        preview_url = reverse(
+            "wagtailadmin_pages:preview_on_edit", args=(self.event_page.id,)
+        )
+
+        response = self.client.post(
+            preview_url,
+            {
+                "carousel_items-TOTAL_FORMS": 0,
+                "carousel_items-INITIAL_FORMS": 0,
+                "speakers-TOTAL_FORMS": 0,
+                "speakers-INITIAL_FORMS": 0,
+                "related_links-TOTAL_FORMS": 0,
+                "related_links-INITIAL_FORMS": 0,
+                "head_counts-TOTAL_FORMS": 0,
+                "head_counts-INITIAL_FORMS": 0,
+            },
+        )
+
+        # Check the JSON response
+        self.assertEqual(response.status_code, 200)
+        self.assertJSONEqual(
+            response.content.decode(),
+            {"is_valid": True, "is_available": True},
+        )
+
+        # Check the user can refresh the preview
+        preview_session_key = f"wagtail-preview-{self.event_page.id}"
+        self.assertIn(preview_session_key, self.client.session)
+
+        response = self.client.get(preview_url)
+
+        # Check the HTML response
+        self.assertEqual(response.status_code, 200)
+        self.assertTemplateUsed(response, "tests/event_page.html")
+        self.assertContains(response, "Placeholder title")
+
     def test_preview_on_edit_expiry(self):
         initial_datetime = timezone.now()
         expiry_datetime = initial_datetime + datetime.timedelta(

wagtail/admin/views/pages/preview.py

@@ -1,7 +1,10 @@
+import uuid
+
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import PermissionDenied
 from django.http import Http404
 from django.shortcuts import get_object_or_404
+from django.utils.translation import gettext
 
 from wagtail.admin.views.generic.preview import PreviewOnEdit as GenericPreviewOnEdit
 from wagtail.models import Page
@@ -43,6 +46,16 @@ class PreviewOnEdit(GenericPreviewOnEdit):
                 for_user=self.request.user,
             )
 
+        query_dict = query_dict.copy()
+
+        if not query_dict.get("title"):
+            query_dict["title"] = gettext("Placeholder title")
+
+        # Generate a random slug if one is not provided, use UUID to ensure
+        # uniqueness without needing to hit the database
+        if not query_dict.get("slug"):
+            query_dict["slug"] = str(uuid.uuid4())
+
         return form_class(
             query_dict,
             instance=self.object,