From a4afffd2ba2f19413712e6165b3f5585907e879b Mon Sep 17 00:00:00 2001
From: Ori Livneh <ori@wikimedia.org>
Date: Tue, 5 Mar 2013 14:43:03 -0800
Subject: [PATCH] Add CategoryAfterPageAdded / CategoryAfterPageRemoved hooks

My first instinct was to derive the hook signature from the implementation and
have a generic 'PageCategoriesUpdated' hook that receives the WikiPage object
and two arrays ($added, $deleted). After some reflection I decided to iterate
through each array and call the hook once per category. I like this way of
doing things because a change in page membership could be thought of from two
directions: it is either the category that is gaining or losing a member, or
the page that is gaining or losing a category.

The category name is sufficient for instantiating a Category object without
additional queries being needed, so my preference was to pass objects rather
than string identifiers.

If implementors of handlers happen to be interested in the set of categories or
pages being updated, it is still the case that they only need to write one
function, and track state using a class property.

Change-Id: Ica4c5fb3acdea6c00678ec0794808fa50a1dd39a
---
 RELEASE-NOTES-1.21    | 1 +
 docs/hooks.txt        | 8 ++++++++
 includes/WikiPage.php | 9 +++++++++
 3 files changed, 18 insertions(+)

diff --git a/RELEASE-NOTES-1.21 b/RELEASE-NOTES-1.21
index 303e0b0fe9..f7dcd2a120 100644
--- a/RELEASE-NOTES-1.21
+++ b/RELEASE-NOTES-1.21
@@ -113,6 +113,7 @@ production.
   gl, hr, hsb, hu, is, it, kk, kl, ku, ky, la, lb, lt, lv, mk, mo, mt, nl, no,
   oc, pl, pt, rm, ro, ru, rup, sco, sk, sl, smn, sq, sr, sv, tk, tl, tr, tt, uk,
   uz, vi.
+* Added 'CategoryAfterPageAdded' and 'CategoryAfterPageRemoved' hooks.
 
 === Bug fixes in 1.21 ===
 * (bug 40353) SpecialDoubleRedirect should support interwiki redirects.
diff --git a/docs/hooks.txt b/docs/hooks.txt
index 28eedf4725..03aa246ffc 100644
--- a/docs/hooks.txt
+++ b/docs/hooks.txt
@@ -745,6 +745,14 @@ $output: OutputPage object in use
 the defaults.
 &$namespaces: Array of namespace numbers with corresponding canonical names
 
+'CategoryAfterPageAdded': After a page is added to a category.
+$category: Category that page was added to
+$wikiPage: WikiPage that was added
+
+'CategoryAfterPageRemoved': After a page is removed from a category.
+$category: Category that page was removed from
+$wikiPage: WikiPage that was removed
+
 'CategoryPageView': Before viewing a categorypage in CategoryPage::view.
 $catpage: CategoryPage instance
 
diff --git a/includes/WikiPage.php b/includes/WikiPage.php
index 604829415b..10b3bd86ae 100644
--- a/includes/WikiPage.php
+++ b/includes/WikiPage.php
@@ -3058,6 +3058,15 @@ class WikiPage implements Page, IDBAccessObject {
 				__METHOD__
 			);
 		}
+
+		foreach( $added as $catName ) {
+			$cat = Category::newFromName( $catName );
+			wfRunHooks( 'CategoryAfterPageAdded', array( $cat, $this ) );
+		}
+		foreach( $deleted as $catName ) {
+			$cat = Category::newFromName( $catName );
+			wfRunHooks( 'CategoryAfterPageRemoved', array( $cat, $this ) );
+		}
 	}
 
 	/**
-- 
2.20.1