Fix for Issue #5975: Adds "Cache-Control: private" in serve_preview to bypass caching. (#5986)

CHANGELOG.txt

@@ -16,6 +16,7 @@ Changelog
  * Fix: Ensure link to add a new user works when no users are visible in the users list (LB (Ben Johnston))
  * Fix: `AbstractEmailForm` saved submission fields are now aligned with the email content fields, `form.cleaned_data` will be used instead of `form.fields` (Haydn Greatnews)
  * Fix: Removed ARIA `role="table"` from TableBlock output (Thibaud Colas)
+ * Fix: Set Cache-Control header to prevent page preview responses from being cached (Tomas Walch)
 
 
 2.9 (xx.xx.xxxx) - IN DEVELOPMENT

docs/releases/2.10.rst

@@ -30,6 +30,7 @@ Bug fixes
  * Ensure link to add a new user works when no users are visible in the users list (LB (Ben Johnston))
  * ``AbstractEmailForm`` saved submission fields are now aligned with the email content fields, ``form.cleaned_data`` will be used instead of ``form.fields`` (Haydn Greatnews)
  * Removed ARIA `role="table"` from TableBlock output (Thibaud Colas)
+ * Set Cache-Control header to prevent page preview responses from being cached (Tomas Walch)
 
 
 Upgrade considerations

wagtail/admin/tests/pages/test_edit_page.py

@@ -8,7 +8,7 @@ from django.contrib.auth.models import Permission
 from django.core import mail
 from django.core.files.base import ContentFile
 from django.http import HttpRequest, HttpResponse
-from django.test import TestCase, modify_settings
+from django.test import TestCase, modify_settings, override_settings
 from django.urls import reverse
 from django.utils import timezone
 
@@ -694,6 +694,35 @@ class TestPageEdit(TestCase, WagtailTestUtils):
             html=True
         )
 
+    @override_settings(CACHES={
+        'default': {
+            'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+        }})
+    @modify_settings(MIDDLEWARE={
+        'append': 'django.middleware.cache.FetchFromCacheMiddleware',
+        'prepend': 'django.middleware.cache.UpdateCacheMiddleware',
+    })
+    def test_preview_does_not_cache(self):
+        '''
+        Tests solution to issue #5975
+        '''
+        post_data = {
+            'title': "I've been edited one time!",
+            'content': "Some content",
+            'slug': 'hello-world',
+            'action-submit': "Submit",
+        }
+        preview_url = reverse('wagtailadmin_pages:preview_on_edit',
+                              args=(self.child_page.id,))
+        self.client.post(preview_url, post_data)
+        response = self.client.get(preview_url)
+        self.assertContains(response, "I've been edited one time!", html=True)
+
+        post_data['title'] = "I've been edited two times!"
+        self.client.post(preview_url, post_data)
+        response = self.client.get(preview_url)
+        self.assertContains(response, "I've been edited two times!", html=True)
+
     @modify_settings(ALLOWED_HOSTS={'append': 'childpage.example.com'})
     def test_preview_uses_correct_site(self):
         # create a Site record for the child page

wagtail/core/models.py

@@ -19,6 +19,7 @@ from django.http import Http404
 from django.template.response import TemplateResponse
 from django.urls import NoReverseMatch, reverse
 from django.utils import timezone
+from django.utils.cache import patch_cache_control
 from django.utils.functional import cached_property
 from django.utils.text import capfirst, slugify
 from django.utils.translation import gettext_lazy as _
@@ -1488,7 +1489,9 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
         """
         request.is_preview = True
 
-        return self.serve(request)
+        response = self.serve(request)
+        patch_cache_control(response, private=True)
+        return response
 
     def get_cached_paths(self):
         """