Merge branch 'kaedroho-foreign-key-system-check'

CHANGELOG.txt

@@ -7,6 +7,7 @@ Changelog
  * Added logging for page operations
  * The save/publish/submit buttons on the page edit page now redirects the user back to the edit page instead of the explorer
  * Signal handlers for ``wagtail.wagtailsearch`` and ``wagtail.contrib.wagtailfrontendcache`` are now automatically registered when using Django 1.7 or above. (Tim Heap)
+ * Added a Django 1.7 system check to ensure that foreign keys from Page models are set to on_delete=SET_NULL, to prevent inadvertent (and tree-breaking) page deletions
  * Fix: Replaced references of .username with .get_username() on users for better custom user model support (John-Scott Atlakson)
  * Fix: Unpinned dependency versions for six and requests to help prevent dependency conflicts
  * Fix: Fixed TypeError when getting embed HTML with oembed on Python 3 (John-Scott Atlakson)

docs/releases/0.8.rst

@@ -18,6 +18,7 @@ Minor features
  * Page operations (creation, publishing, copying etc) are now logged via Python's ``logging`` framework; to configure this, add a logger entry for ``'wagtail'`` or ``'wagtail.core'`` to the ``LOGGING`` setup in your settings file.
  * The save/publish/submit buttons on the page edit page now redirects the user back to the edit page instead of the explorer
  * Signal handlers for ``wagtail.wagtailsearch`` and ``wagtail.contrib.wagtailfrontendcache`` are now automatically registered when using Django 1.7 or above.
+ * Added a Django 1.7 system check to ensure that foreign keys from Page models are set to ``on_delete=SET_NULL``, to prevent inadvertent (and tree-breaking) page deletions
 
 
 Bug fixes

wagtail/wagtailcore/models.py

@@ -26,6 +26,11 @@ from django.core.exceptions import ValidationError, ImproperlyConfigured
 from django.utils.functional import cached_property
 from django.utils.encoding import python_2_unicode_compatible
 
+try:
+    from django.core import checks
+except ImportError:
+    pass
+
 from treebeard.mp_tree import MP_Node
 
 from wagtail.wagtailcore.utils import camelcase_to_underscore, resolve_model_string
@@ -263,7 +268,7 @@ class Page(six.with_metaclass(PageBase, MP_Node, ClusterableModel, index.Indexed
     live = models.BooleanField(default=True, editable=False)
     has_unpublished_changes = models.BooleanField(default=False, editable=False)
     url_path = models.CharField(max_length=255, blank=True, editable=False)
-    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True, editable=False, related_name='owned_pages')
+    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True, editable=False, on_delete=models.SET_NULL, related_name='owned_pages')
 
     seo_title = models.CharField(verbose_name=_("Page title"), max_length=255, blank=True, help_text=_("Optional. 'Search Engine Friendly' title. This will appear at the top of the browser window."))
     show_in_menus = models.BooleanField(default=False, help_text=_("Whether a link to this page will appear in automatically generated menus"))
@@ -352,6 +357,28 @@ class Page(six.with_metaclass(PageBase, MP_Node, ClusterableModel, index.Indexed
 
         return result
 
+    @classmethod
+    def check(cls, **kwargs):
+        errors = super(Page, cls).check(**kwargs)
+
+        # Check that foreign keys from pages are not configured to cascade
+        # This is the default Django behaviour which must be explicitly overridden
+        # to prevent pages disappearing unexpectedly and the tree being corrupted
+
+        for field in cls._meta.fields:
+            if isinstance(field, models.ForeignKey) and field.name not in ['page_ptr', 'content_type']:
+                if field.rel.on_delete == models.CASCADE:
+                    errors.append(
+                        checks.Error(
+                            "Field hasn't specified on_delete action",
+                            hint="Set on_delete=models.SET_NULL and make sure the field is nullable.",
+                            obj=field,
+                            id='wagtailcore.E001',
+                        )
+                    )
+
+        return errors
+
     def _update_descendant_url_paths(self, old_url_path, new_url_path):
         cursor = connection.cursor()
         if connection.vendor == 'sqlite':