Add code example for `before_delete_page` hook

CHANGELOG.txt

@@ -29,6 +29,7 @@ Changelog
  * Add `label_format` attribute to customise the label shown for a collapsed StructBlock (Matt Westcott)
  * User Group permissions will now show all custom object permissions in one row instead of a separate table (Kamil Marut)User Group permissions editing in the admin will now show all custom object permissions in one row instead of a separate table (Kamil Marut)
  * Create `ImageFileMixin` to extract shared file handling methods from `AbstractImage` and `AbstractRendition` (Fabien Le Frapper)
+ * Add `before_delete_page` example to Hooks documentation (Jane Liu)
  * Fix: Delete button is now correct colour on snippets and modeladmin listings (Brandon Murch)
  * Fix: Ensure that StreamBlock / ListBlock-level validation errors are counted towards error counts (Matt Westcott)
  * Fix: InlinePanel add button is now keyboard navigatable (Jesse Menn)

CONTRIBUTORS.rst

@@ -541,6 +541,7 @@ Contributors
 * Bryan Williams
 * Wout De Puysseleir
 * Kamil Marut
+* Jane Liu
 
 Translators
 ===========

docs/reference/hooks.rst

@@ -605,8 +605,26 @@ Hooks for customising the way users are directed through the process of creating
 
   Called at the beginning of the "delete page" view passing in the request and the page object.
 
-  Uses the same behaviour as ``before_create_page``.
+  Uses the same behaviour as ``before_create_page``, is is run both for both ``GET`` and ``POST`` requests.
 
+ .. code-block:: python
+
+    from django.shortcuts import redirect
+    from django.utils.html import format_html
+
+    from wagtail.admin import messages
+    from wagtail.core import hooks
+
+    from .models import AwesomePage
+
+
+    @hooks.register('before_delete_page')
+    def before_delete_page(request, page):
+        """Block awesome page deletion and show a message."""
+
+        if request.method == 'POST' and page.specific_class in [AwesomePage]:
+            messages.warning(request, "Awesome pages cannot be deleted, only unpublished")
+            return redirect('wagtailadmin_pages:delete', page.pk)
 
 .. _after_edit_page:
 

docs/releases/2.15.rst

@@ -40,6 +40,7 @@ Other features
  * Add ``label_format`` attribute to customise the label shown for a collapsed StructBlock (Matt Westcott)
  * User Group permissions editing in the admin will now show all custom object permissions in one row instead of a separate table (Kamil Marut)
  * Create ``ImageFileMixin`` to extract shared file handling methods from ``AbstractImage`` and ``AbstractRendition`` (Fabien Le Frapper)
+ * Add ``before_delete_page`` example to Hooks documentation (Jane Liu)
 
 Bug fixes
 ~~~~~~~~~