From 247ecab445dcfee7b75dda887e1e889639c090c7 Mon Sep 17 00:00:00 2001
From: Kunal Mehta <legoktm@gmail.com>
Date: Wed, 17 Dec 2014 11:18:49 -0800
Subject: [PATCH] SpecialTrackingCategories: Read from the extension registry

This demonstrates how we can transition from extensions putting
things into the global scope ($wgTrackingCategories) to instead
storing them in the extension registry. This will increase the
overall performance of the extension registry since it no
longer needs to do an array_merge with $wgTrackingCategories.

For extensions already converted to using the registry
no change is needed as the schema is still the same.

Change-Id: Ie0df4c20b123dac784a1c02eb991edc609a911b6
---
 includes/DefaultSettings.php                  | 16 +++---------
 includes/parser/ParserOutput.php              |  7 +++---
 includes/registration/ExtensionProcessor.php  |  1 -
 .../specials/SpecialTrackingCategories.php    | 25 ++++++++++++++++++-
 4 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index ee462d84ad..6d399cf4d7 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -3845,20 +3845,12 @@ $wgNamespacesWithSubpages = array(
  * A message with the suffix '-desc' should be added as a description message
  * to have extra information on Special:TrackingCategories.
  *
+ * @deprecated since 1.25 Extensions should now register tracking categories using
+ *                        the new extension registration system.
+ *
  * @since 1.23
  */
-$wgTrackingCategories = array(
-	'index-category',
-	'noindex-category',
-	'duplicate-args-category',
-	'expensive-parserfunction-category',
-	'post-expand-template-argument-category',
-	'post-expand-template-inclusion-category',
-	'hidden-category-category',
-	'broken-file-category',
-	'node-count-exceeded-category',
-	'expansion-depth-exceeded-category',
-);
+$wgTrackingCategories = array();
 
 /**
  * Array of namespaces which can be deemed to contain valid "content", as far
diff --git a/includes/parser/ParserOutput.php b/includes/parser/ParserOutput.php
index 117e04a122..e9e72beca8 100644
--- a/includes/parser/ParserOutput.php
+++ b/includes/parser/ParserOutput.php
@@ -489,9 +489,10 @@ class ParserOutput extends CacheTime {
 	 * Add a tracking category, getting the title from a system message,
 	 * or print a debug message if the title is invalid.
 	 *
-	 * Please add any message that you use with this function to
-	 * $wgTrackingCategories. That way they will be listed on
-	 * Special:TrackingCategories.
+	 * Any message used with this function should be registered so it will
+	 * show up on Special:TrackingCategories. Core messages should be added
+	 * to SpecialTrackingCategories::$coreTrackingCategories, and extensions
+	 * should add to "TrackingCategories" in their extension.json.
 	 *
 	 * @param string $msg Message key
 	 * @param Title $title title of the page which is being tracked
diff --git a/includes/registration/ExtensionProcessor.php b/includes/registration/ExtensionProcessor.php
index 459d95b17b..27c8148222 100644
--- a/includes/registration/ExtensionProcessor.php
+++ b/includes/registration/ExtensionProcessor.php
@@ -11,7 +11,6 @@ class ExtensionProcessor implements Processor {
 		'ResourceLoaderSources',
 		'ResourceLoaderLESSVars',
 		'ResourceLoaderLESSImportPaths',
-		'TrackingCategories',
 		'DefaultUserOptions',
 		'HiddenPrefs',
 		'GroupPermissions',
diff --git a/includes/specials/SpecialTrackingCategories.php b/includes/specials/SpecialTrackingCategories.php
index 7684c05117..d219c99d03 100644
--- a/includes/specials/SpecialTrackingCategories.php
+++ b/includes/specials/SpecialTrackingCategories.php
@@ -36,6 +36,24 @@ class SpecialTrackingCategories extends SpecialPage {
 		parent::__construct( 'TrackingCategories' );
 	}
 
+	/**
+	 * Tracking categories that exist in core
+	 *
+	 * @var array
+	 */
+	private static $coreTrackingCategories = array(
+		'index-category',
+		'noindex-category',
+		'duplicate-args-category',
+		'expensive-parserfunction-category',
+		'post-expand-template-argument-category',
+		'post-expand-template-inclusion-category',
+		'hidden-category-category',
+		'broken-file-category',
+		'node-count-exceeded-category',
+		'expansion-depth-exceeded-category',
+	);
+
 	function execute( $par ) {
 		$this->setHeaders();
 		$this->outputHeader();
@@ -120,8 +138,13 @@ class SpecialTrackingCategories extends SpecialPage {
 	 * @return array Array( 'msg' => Title, 'cats' => Title[] )
 	 */
 	private function prepareTrackingCategoriesData() {
+		$categories = array_merge(
+			self::$coreTrackingCategories,
+			ExtensionRegistry::getInstance()->getAttribute( 'TrackingCategories' ),
+			$this->getConfig()->get( 'TrackingCategories' ) // deprecated
+		);
 		$trackingCategories = array();
-		foreach ( $this->getConfig()->get( 'TrackingCategories' ) as $catMsg ) {
+		foreach ( $categories as $catMsg ) {
 			/*
 			 * Check if the tracking category varies by namespace
 			 * Otherwise only pages in the current namespace will be displayed
-- 
2.20.1