1 files changed, 192 insertions, 90 deletions

diff --git a/includes/resourceloader/ResourceLoader.php b/includes/resourceloader/ResourceLoader.php
index 7b87f9d4..6380efcf 100644
--- a/includes/resourceloader/ResourceLoader.php
+++ b/includes/resourceloader/ResourceLoader.php
@@ -39,7 +39,7 @@ class ResourceLoader {
 
 	/** Associative array mapping module name to info associative array */
 	protected $moduleInfos = array();
- 
+
 	/** Associative array mapping framework ids to a list of names of test suite modules */
 	/** like array( 'qunit' => array( 'mediawiki.tests.qunit.suites', 'ext.foo.tests', .. ), .. ) */
 	protected $testModuleNames = array();
@@ -47,6 +47,9 @@ class ResourceLoader {
 	/** array( 'source-id' => array( 'loadScript' => 'http://.../load.php' ) ) **/
 	protected $sources = array();
 
+	/** @var bool */
+	protected $hasErrors = false;
+
 	/* Protected Methods */
 
 	/**
@@ -60,7 +63,7 @@ class ResourceLoader {
 	 * requests its own information. This sacrifice of modularity yields a substantial
 	 * performance improvement.
 	 *
-	 * @param $modules Array: List of module names to preload information for
+	 * @param array $modules List of module names to preload information for
 	 * @param $context ResourceLoaderContext: Context to load the information within
 	 */
 	public function preloadModuleInfo( array $modules, ResourceLoaderContext $context ) {
@@ -127,8 +130,8 @@ class ResourceLoader {
 	 * If $data is empty, only contains whitespace or the filter was unknown,
 	 * $data is returned unmodified.
 	 *
-	 * @param $filter String: Name of filter to run
-	 * @param $data String: Text to filter, such as JavaScript or CSS text
+	 * @param string $filter Name of filter to run
+	 * @param string $data Text to filter, such as JavaScript or CSS text
 	 * @return String: Filtered data, or a comment containing an error message
 	 */
 	protected function filter( $filter, $data ) {
@@ -150,6 +153,7 @@ class ResourceLoader {
 		$cache = wfGetCache( CACHE_ANYTHING );
 		$cacheEntry = $cache->get( $key );
 		if ( is_string( $cacheEntry ) ) {
+			wfIncrStats( "rl-$filter-cache-hits" );
 			wfProfileOut( __METHOD__ );
 			return $cacheEntry;
 		}
@@ -157,6 +161,7 @@ class ResourceLoader {
 		$result = '';
 		// Run the filter - we've already verified one of these will work
 		try {
+			wfIncrStats( "rl-$filter-cache-misses" );
 			switch ( $filter ) {
 				case 'minify-js':
 					$result = JavaScriptMinifier::minify( $data,
@@ -173,10 +178,12 @@ class ResourceLoader {
 
 			// Save filtered text to Memcached
 			$cache->set( $key, $result );
-		} catch ( Exception $exception ) {
-			// Return exception as a comment
-			$result = $this->makeComment( $exception->__toString() );
+		} catch ( Exception $e ) {
+			MWExceptionHandler::logException( $e );
+			wfDebugLog( 'resourceloader', __METHOD__ . ": minification failed: $e" );
 			$this->hasErrors = true;
+			// Return exception as a comment
+			$result = self::formatException( $e );
 		}
 
 		wfProfileOut( __METHOD__ );
@@ -201,7 +208,7 @@ class ResourceLoader {
 		$this->addSource( $wgResourceLoaderSources );
 
 		// Register core modules
-		$this->register( include( "$IP/resources/Resources.php" ) );
+		$this->register( include "$IP/resources/Resources.php" );
 		// Register extension modules
 		wfRunHooks( 'ResourceLoaderRegisterModules', array( &$this ) );
 		$this->register( $wgResourceModules );
@@ -210,7 +217,6 @@ class ResourceLoader {
 			$this->registerTestModules();
 		}
 
-
 		wfProfileOut( __METHOD__ );
 	}
 
@@ -218,7 +224,7 @@ class ResourceLoader {
 	 * Registers a module with the ResourceLoader system.
 	 *
 	 * @param $name Mixed: Name of module as a string or List of name/object pairs as an array
-	 * @param $info array Module info array. For backwards compatibility with 1.17alpha,
+	 * @param array $info Module info array. For backwards compatibility with 1.17alpha,
 	 *   this may also be a ResourceLoaderModule object. Optional when using
 	 *   multiple-registration calling style.
 	 * @throws MWException: If a duplicate module registration is attempted
@@ -235,6 +241,7 @@ class ResourceLoader {
 		foreach ( $registrations as $name => $info ) {
 			// Disallow duplicate registrations
 			if ( isset( $this->moduleInfos[$name] ) ) {
+				wfProfileOut( __METHOD__ );
 				// A module has already been registered by this name
 				throw new MWException(
 					'ResourceLoader duplicate registration error. ' .
@@ -244,6 +251,7 @@ class ResourceLoader {
 
 			// Check $name for validity
 			if ( !self::isValidModuleName( $name ) ) {
+				wfProfileOut( __METHOD__ );
 				throw new MWException( "ResourceLoader module name '$name' is invalid, see ResourceLoader::isValidModuleName()" );
 			}
 
@@ -252,6 +260,7 @@ class ResourceLoader {
 				// Old calling convention
 				// Validate the input
 				if ( !( $info instanceof ResourceLoaderModule ) ) {
+					wfProfileOut( __METHOD__ );
 					throw new MWException( 'ResourceLoader invalid module error. ' .
 						'Instances of ResourceLoaderModule expected.' );
 				}
@@ -274,24 +283,28 @@ class ResourceLoader {
 		global $IP, $wgEnableJavaScriptTest;
 
 		if ( $wgEnableJavaScriptTest !== true ) {
-			throw new MWException( 'Attempt to register JavaScript test modules but <tt>$wgEnableJavaScriptTest</tt> is false. Edit your <tt>LocalSettings.php</tt> to enable it.' );
+			throw new MWException( 'Attempt to register JavaScript test modules but <code>$wgEnableJavaScriptTest</code> is false. Edit your <code>LocalSettings.php</code> to enable it.' );
 		}
 
 		wfProfileIn( __METHOD__ );
 
 		// Get core test suites
 		$testModules = array();
-		$testModules['qunit'] = include( "$IP/tests/qunit/QUnitTestResources.php" );
+		$testModules['qunit'] = include "$IP/tests/qunit/QUnitTestResources.php";
 		// Get other test suites (e.g. from extensions)
 		wfRunHooks( 'ResourceLoaderTestModules', array( &$testModules, &$this ) );
 
 		// Add the testrunner (which configures QUnit) to the dependencies.
 		// Since it must be ready before any of the test suites are executed.
-		foreach( $testModules['qunit'] as $moduleName => $moduleProps ) {
-			$testModules['qunit'][$moduleName]['dependencies'][] = 'mediawiki.tests.qunit.testrunner';
+		foreach ( $testModules['qunit'] as &$module ) {
+			// Make sure all test modules are top-loading so that when QUnit starts
+			// on document-ready, it will run once and finish. If some tests arrive
+			// later (possibly after QUnit has already finished) they will be ignored.
+			$module['position'] = 'top';
+			$module['dependencies'][] = 'mediawiki.tests.qunit.testrunner';
 		}
 
-		foreach( $testModules as $id => $names ) {
+		foreach ( $testModules as $id => $names ) {
 			// Register test modules
 			$this->register( $testModules[$id] );
 
@@ -309,9 +322,10 @@ class ResourceLoader {
 	 * 'loadScript': URL (either fully-qualified or protocol-relative) of load.php for this source
 	 *
 	 * @param $id Mixed: source ID (string), or array( id1 => props1, id2 => props2, ... )
-	 * @param $properties Array: source properties
+	 * @param array $properties source properties
+	 * @throws MWException
 	 */
-	public function addSource( $id, $properties = null) {
+	public function addSource( $id, $properties = null ) {
 		// Allow multiple sources to be registered in one call
 		if ( is_array( $id ) ) {
 			foreach ( $id as $key => $value ) {
@@ -346,18 +360,18 @@ class ResourceLoader {
 	public function getModuleNames() {
 		return array_keys( $this->moduleInfos );
 	}
- 
- 	/**
+
+	/**
 	 * Get a list of test module names for one (or all) frameworks.
 	 * If the given framework id is unknkown, or if the in-object variable is not an array,
 	 * then it will return an empty array.
 	 *
-	 * @param $framework String: Optional. Get only the test module names for one
+	 * @param string $framework Optional. Get only the test module names for one
 	 * particular framework.
 	 * @return Array
 	 */
 	public function getTestModuleNames( $framework = 'all' ) {
-		/// @TODO: api siteinfo prop testmodulenames modulenames
+		/// @todo api siteinfo prop testmodulenames modulenames
 		if ( $framework == 'all' ) {
 			return $this->testModuleNames;
 		} elseif ( isset( $this->testModuleNames[$framework] ) && is_array( $this->testModuleNames[$framework] ) ) {
@@ -370,7 +384,7 @@ class ResourceLoader {
 	/**
 	 * Get the ResourceLoaderModule object for a given module name.
 	 *
-	 * @param $name String: Module name
+	 * @param string $name Module name
 	 * @return ResourceLoaderModule if module has been registered, null otherwise
 	 */
 	public function getModule( $name ) {
@@ -381,6 +395,7 @@ class ResourceLoader {
 			}
 			// Construct the requested object
 			$info = $this->moduleInfos[$name];
+			/** @var ResourceLoaderModule $object */
 			if ( isset( $info['object'] ) ) {
 				// Object given in info array
 				$object = $info['object'];
@@ -435,7 +450,6 @@ class ResourceLoader {
 
 		wfProfileIn( __METHOD__ );
 		$errors = '';
-		$this->hasErrors = false;
 
 		// Split requested modules into two groups, modules and missing
 		$modules = array();
@@ -446,11 +460,14 @@ class ResourceLoader {
 				// Do not allow private modules to be loaded from the web.
 				// This is a security issue, see bug 34907.
 				if ( $module->getGroup() === 'private' ) {
-					$errors .= $this->makeComment( "Cannot show private module \"$name\"" );
+					wfDebugLog( 'resourceloader', __METHOD__ . ": request for private module '$name' denied" );
 					$this->hasErrors = true;
+					// Add exception to the output as a comment
+					$errors .= self::makeComment( "Cannot show private module \"$name\"" );
+
 					continue;
 				}
-				$modules[$name] = $this->getModule( $name );
+				$modules[$name] = $module;
 			} else {
 				$missing[] = $name;
 			}
@@ -459,13 +476,15 @@ class ResourceLoader {
 		// Preload information needed to the mtime calculation below
 		try {
 			$this->preloadModuleInfo( array_keys( $modules ), $context );
-		} catch( Exception $e ) {
-			// Add exception to the output as a comment
-			$errors .= $this->makeComment( $e->__toString() );
+		} catch ( Exception $e ) {
+			MWExceptionHandler::logException( $e );
+			wfDebugLog( 'resourceloader', __METHOD__ . ": preloading module info failed: $e" );
 			$this->hasErrors = true;
+			// Add exception to the output as a comment
+			$errors .= self::formatException( $e );
 		}
 
-		wfProfileIn( __METHOD__.'-getModifiedTime' );
+		wfProfileIn( __METHOD__ . '-getModifiedTime' );
 
 		// To send Last-Modified and support If-Modified-Since, we need to detect
 		// the last modified time
@@ -478,13 +497,15 @@ class ResourceLoader {
 				// Calculate maximum modified time
 				$mtime = max( $mtime, $module->getModifiedTime( $context ) );
 			} catch ( Exception $e ) {
-				// Add exception to the output as a comment
-				$errors .= $this->makeComment( $e->__toString() );
+				MWExceptionHandler::logException( $e );
+				wfDebugLog( 'resourceloader', __METHOD__ . ": calculating maximum modified time failed: $e" );
 				$this->hasErrors = true;
+				// Add exception to the output as a comment
+				$errors .= self::formatException( $e );
 			}
 		}
 
-		wfProfileOut( __METHOD__.'-getModifiedTime' );
+		wfProfileOut( __METHOD__ . '-getModifiedTime' );
 
 		// If there's an If-Modified-Since header, respond with a 304 appropriately
 		if ( $this->tryRespondLastModified( $context, $mtime ) ) {
@@ -501,7 +522,7 @@ class ResourceLoader {
 		// Capture any PHP warnings from the output buffer and append them to the
 		// response in a comment if we're in debug mode.
 		if ( $context->getDebug() && strlen( $warnings = ob_get_contents() ) ) {
-			$response = $this->makeComment( $warnings ) . $response;
+			$response = self::makeComment( $warnings ) . $response;
 			$this->hasErrors = true;
 		}
 
@@ -530,8 +551,8 @@ class ResourceLoader {
 	/**
 	 * Send content type and last modified headers to the client.
 	 * @param $context ResourceLoaderContext
-	 * @param $mtime string TS_MW timestamp to use for last-modified
-	 * @param $error bool Whether there are commented-out errors in the response
+	 * @param string $mtime TS_MW timestamp to use for last-modified
+	 * @param bool $errors Whether there are commented-out errors in the response
 	 * @return void
 	 */
 	protected function sendResponseHeaders( ResourceLoaderContext $context, $mtime, $errors ) {
@@ -540,16 +561,17 @@ class ResourceLoader {
 		// to propagate to clients quickly
 		// If there were errors, we also need a shorter expiry time so we can recover quickly
 		if ( is_null( $context->getVersion() ) || $errors ) {
-			$maxage  = $wgResourceLoaderMaxage['unversioned']['client'];
+			$maxage = $wgResourceLoaderMaxage['unversioned']['client'];
 			$smaxage = $wgResourceLoaderMaxage['unversioned']['server'];
 		// If a version was specified we can use a longer expiry time since changing
 		// version numbers causes cache misses
 		} else {
-			$maxage  = $wgResourceLoaderMaxage['versioned']['client'];
+			$maxage = $wgResourceLoaderMaxage['versioned']['client'];
 			$smaxage = $wgResourceLoaderMaxage['versioned']['server'];
 		}
 		if ( $context->getOnly() === 'styles' ) {
 			header( 'Content-Type: text/css; charset=utf-8' );
+			header( 'Access-Control-Allow-Origin: *' );
 		} else {
 			header( 'Content-Type: text/javascript; charset=utf-8' );
 		}
@@ -569,8 +591,8 @@ class ResourceLoader {
 	 * If there's an If-Modified-Since header, respond with a 304 appropriately
 	 * and clear out the output buffer. If the client cache is too old then do nothing.
 	 * @param $context ResourceLoaderContext
-	 * @param $mtime string The TS_MW timestamp to check the header against
-	 * @return bool True iff 304 header sent and output handled
+	 * @param string $mtime The TS_MW timestamp to check the header against
+	 * @return bool True if 304 header sent and output handled
 	 */
 	protected function tryRespondLastModified( ResourceLoaderContext $context, $mtime ) {
 		// If there's an If-Modified-Since header, respond with a 304 appropriately
@@ -590,13 +612,7 @@ class ResourceLoader {
 				// See also http://bugs.php.net/bug.php?id=51579
 				// To work around this, we tear down all output buffering before
 				// sending the 304.
-				// On some setups, ob_get_level() doesn't seem to go down to zero
-				// no matter how often we call ob_get_clean(), so instead of doing
-				// the more intuitive while ( ob_get_level() > 0 ) ob_get_clean();
-				// we have to be safe here and avoid an infinite loop.
-				for ( $i = 0; $i < ob_get_level(); $i++ ) {
-					ob_end_clean();
-				}
+				wfResetOutputBuffers( /* $resetGzipEncoding = */ true );
 
 				header( 'HTTP/1.0 304 Not Modified' );
 				header( 'Status: 304 Not Modified' );
@@ -628,7 +644,7 @@ class ResourceLoader {
 		if ( !$good ) {
 			try { // RL always hits the DB on file cache miss...
 				wfGetDB( DB_SLAVE );
-			} catch( DBConnectionError $e ) { // ...check if we need to fallback to cache
+			} catch ( DBConnectionError $e ) { // ...check if we need to fallback to cache
 				$good = $fileCache->isCacheGood(); // cache existence check
 			}
 		}
@@ -657,22 +673,45 @@ class ResourceLoader {
 		return false; // cache miss
 	}
 
-	protected function makeComment( $text ) {
+	/**
+	 * Generate a CSS or JS comment block. Only use this for public data,
+	 * not error message details.
+	 *
+	 * @param $text string
+	 * @return string
+	 */
+	public static function makeComment( $text ) {
 		$encText = str_replace( '*/', '* /', $text );
 		return "/*\n$encText\n*/\n";
 	}
 
 	/**
+	 * Handle exception display
+	 *
+	 * @param Exception $e to be shown to the user
+	 * @return string sanitized text that can be returned to the user
+	 */
+	public static function formatException( $e ) {
+		global $wgShowExceptionDetails;
+
+		if ( $wgShowExceptionDetails ) {
+			return self::makeComment( $e->__toString() );
+		} else {
+			return self::makeComment( wfMessage( 'internalerror' )->text() );
+		}
+	}
+
+	/**
 	 * Generates code for a response
 	 *
 	 * @param $context ResourceLoaderContext: Context in which to generate a response
-	 * @param $modules Array: List of module objects keyed by module name
-	 * @param $missing Array: List of unavailable modules (optional)
+	 * @param array $modules List of module objects keyed by module name
+	 * @param array $missing List of unavailable modules (optional)
 	 * @return String: Response data
 	 */
 	public function makeModuleResponse( ResourceLoaderContext $context,
-		array $modules, $missing = array() )
-	{
+		array $modules, $missing = array()
+	) {
 		$out = '';
 		$exceptions = '';
 		if ( $modules === array() && $missing === array() ) {
@@ -685,9 +724,11 @@ class ResourceLoader {
 			try {
 				$blobs = MessageBlobStore::get( $this, $modules, $context->getLanguage() );
 			} catch ( Exception $e ) {
-				// Add exception to the output as a comment
-				$exceptions .= $this->makeComment( $e->__toString() );
+				MWExceptionHandler::logException( $e );
+				wfDebugLog( 'resourceloader', __METHOD__ . ": pre-fetching blobs from MessageBlobStore failed: $e" );
 				$this->hasErrors = true;
+				// Add exception to the output as a comment
+				$exceptions .= self::formatException( $e );
 			}
 		} else {
 			$blobs = array();
@@ -791,9 +832,11 @@ class ResourceLoader {
 						break;
 				}
 			} catch ( Exception $e ) {
-				// Add exception to the output as a comment
-				$exceptions .= $this->makeComment( $e->__toString() );
+				MWExceptionHandler::logException( $e );
+				wfDebugLog( 'resourceloader', __METHOD__ . ": generating module package failed: $e" );
 				$this->hasErrors = true;
+				// Add exception to the output as a comment
+				$exceptions .= self::formatException( $e );
 
 				// Register module as missing
 				$missing[] = $name;
@@ -834,7 +877,7 @@ class ResourceLoader {
 	 * Returns JS code to call to mw.loader.implement for a module with
 	 * given properties.
 	 *
-	 * @param $name string Module name
+	 * @param string $name Module name
 	 * @param $scripts Mixed: List of URLs to JavaScript files or String of JavaScript code
 	 * @param $styles Mixed: Array of CSS strings keyed by media type, or an array of lists of URLs to
 	 * CSS files keyed by media type
@@ -842,6 +885,7 @@ class ResourceLoader {
 	 *     associative array mapping message key to value, or a JSON-encoded message blob containing
 	 *     the same data, wrapped in an XmlJsCode object.
 	 *
+	 * @throws MWException
 	 * @return string
 	 */
 	public static function makeLoaderImplementScript( $name, $scripts, $styles, $messages ) {
@@ -862,7 +906,9 @@ class ResourceLoader {
 				// output javascript "[]" instead of "{}". This fixes that.
 				(object)$styles,
 				(object)$messages
-			) );
+			),
+			ResourceLoader::inDebugMode()
+		);
 	}
 
 	/**
@@ -881,7 +927,7 @@ class ResourceLoader {
 	 * Combines an associative array mapping media type to CSS into a
 	 * single stylesheet with "@media" blocks.
 	 *
-	 * @param $styles Array: Array keyed by media type containing (arrays of) CSS strings.
+	 * @param array $stylePairs Array keyed by media type containing (arrays of) CSS strings.
 	 *
 	 * @return Array
 	 */
@@ -891,7 +937,7 @@ class ResourceLoader {
 			// ResourceLoaderFileModule::getStyle can return the styles
 			// as a string or an array of strings. This is to allow separation in
 			// the front-end.
-			$styles = (array) $styles;
+			$styles = (array)$styles;
 			foreach ( $styles as $style ) {
 				$style = trim( $style );
 				// Don't output an empty "@media print { }" block (bug 40498)
@@ -902,7 +948,7 @@ class ResourceLoader {
 
 					if ( $media === '' || $media == 'all' ) {
 						$out[] = $style;
-					} else if ( is_string( $media ) ) {
+					} elseif ( is_string( $media ) ) {
 						$out[] = "@media $media {\n" . str_replace( "\n", "\n\t", "\t" . $style ) . "}";
 					}
 					// else: skip
@@ -941,12 +987,12 @@ class ResourceLoader {
 	 * which will have values corresponding to $name, $version, $dependencies
 	 * and $group as supplied.
 	 *
-	 * @param $name String: Module name
+	 * @param string $name Module name
 	 * @param $version Integer: Module version number as a timestamp
-	 * @param $dependencies Array: List of module names on which this module depends
-	 * @param $group String: Group which the module is in.
-	 * @param $source String: Source of the module, or 'local' if not foreign.
-	 * @param $script String: JavaScript code
+	 * @param array $dependencies List of module names on which this module depends
+	 * @param string $group Group which the module is in.
+	 * @param string $source Source of the module, or 'local' if not foreign.
+	 * @param string $script JavaScript code
 	 *
 	 * @return string
 	 */
@@ -974,21 +1020,21 @@ class ResourceLoader {
 	 *     ) ):
 	 *        Registers modules with the given names and parameters.
 	 *
-	 * @param $name String: Module name
+	 * @param string $name Module name
 	 * @param $version Integer: Module version number as a timestamp
-	 * @param $dependencies Array: List of module names on which this module depends
-	 * @param $group String: group which the module is in.
-	 * @param $source String: source of the module, or 'local' if not foreign
+	 * @param array $dependencies List of module names on which this module depends
+	 * @param string $group group which the module is in.
+	 * @param string $source source of the module, or 'local' if not foreign
 	 *
 	 * @return string
 	 */
 	public static function makeLoaderRegisterScript( $name, $version = null,
-		$dependencies = null, $group = null, $source = null )
-	{
+		$dependencies = null, $group = null, $source = null
+	) {
 		if ( is_array( $name ) ) {
 			return Xml::encodeJsCall( 'mw.loader.register', array( $name ) );
 		} else {
-			$version = (int) $version > 1 ? (int) $version : 1;
+			$version = (int)$version > 1 ? (int)$version : 1;
 			return Xml::encodeJsCall( 'mw.loader.register',
 				array( $name, $version, $dependencies, $group, $source ) );
 		}
@@ -1004,8 +1050,8 @@ class ResourceLoader {
 	 *   - ResourceLoader::makeLoaderSourcesScript( array( $id1 => $props1, $id2 => $props2, ... ) );
 	 *       Register sources with the given IDs and properties.
 	 *
-	 * @param $id String: source ID
-	 * @param $properties Array: source properties (see addSource())
+	 * @param string $id source ID
+	 * @param array $properties source properties (see addSource())
 	 *
 	 * @return string
 	 */
@@ -1021,7 +1067,7 @@ class ResourceLoader {
 	 * Returns JS code which runs given JS code if the client-side framework is
 	 * present.
 	 *
-	 * @param $script String: JavaScript code
+	 * @param string $script JavaScript code
 	 *
 	 * @return string
 	 */
@@ -1033,12 +1079,12 @@ class ResourceLoader {
 	 * Returns JS code which will set the MediaWiki configuration array to
 	 * the given value.
 	 *
-	 * @param $configuration Array: List of configuration values keyed by variable name
+	 * @param array $configuration List of configuration values keyed by variable name
 	 *
 	 * @return string
 	 */
 	public static function makeConfigSetScript( array $configuration ) {
-		return Xml::encodeJsCall( 'mw.config.set', array( $configuration ) );
+		return Xml::encodeJsCall( 'mw.config.set', array( $configuration ), ResourceLoader::inDebugMode() );
 	}
 
 	/**
@@ -1046,7 +1092,7 @@ class ResourceLoader {
 	 *
 	 * For example, array( 'foo.bar', 'foo.baz', 'bar.baz', 'bar.quux' )
 	 * becomes 'foo.bar,baz|bar.baz,quux'
-	 * @param $modules array of module names (strings)
+	 * @param array $modules of module names (strings)
 	 * @return string Packed query string
 	 */
 	public static function makePackedModulesString( $modules ) {
@@ -1084,16 +1130,16 @@ class ResourceLoader {
 
 	/**
 	 * Build a load.php URL
-	 * @param $modules array of module names (strings)
-	 * @param $lang string Language code
-	 * @param $skin string Skin name
-	 * @param $user string|null User name. If null, the &user= parameter is omitted
-	 * @param $version string|null Versioning timestamp
-	 * @param $debug bool Whether the request should be in debug mode
-	 * @param $only string|null &only= parameter
-	 * @param $printable bool Printable mode
-	 * @param $handheld bool Handheld mode
-	 * @param $extraQuery array Extra query parameters to add
+	 * @param array $modules of module names (strings)
+	 * @param string $lang Language code
+	 * @param string $skin Skin name
+	 * @param string|null $user User name. If null, the &user= parameter is omitted
+	 * @param string|null $version Versioning timestamp
+	 * @param bool $debug Whether the request should be in debug mode
+	 * @param string|null $only &only= parameter
+	 * @param bool $printable Printable mode
+	 * @param bool $handheld Handheld mode
+	 * @param array $extraQuery Extra query parameters to add
 	 * @return string URL to load.php. May be protocol-relative (if $wgLoadScript is procol-relative)
 	 */
 	public static function makeLoaderURL( $modules, $lang, $skin, $user = null, $version = null, $debug = false, $only = null,
@@ -1111,6 +1157,18 @@ class ResourceLoader {
 	/**
 	 * Build a query array (array representation of query string) for load.php. Helper
 	 * function for makeLoaderURL().
+	 *
+	 * @param array $modules
+	 * @param string $lang
+	 * @param string $skin
+	 * @param string $user
+	 * @param string $version
+	 * @param bool $debug
+	 * @param string $only
+	 * @param bool $printable
+	 * @param bool $handheld
+	 * @param array $extraQuery
+	 *
 	 * @return array
 	 */
 	public static function makeLoaderQuery( $modules, $lang, $skin, $user = null, $version = null, $debug = false, $only = null,
@@ -1149,10 +1207,54 @@ class ResourceLoader {
 	 * Module names may not contain pipes (|), commas (,) or exclamation marks (!) and can be
 	 * at most 255 bytes.
 	 *
-	 * @param $moduleName string Module name to check
+	 * @param string $moduleName Module name to check
 	 * @return bool Whether $moduleName is a valid module name
 	 */
 	public static function isValidModuleName( $moduleName ) {
 		return !preg_match( '/[|,!]/', $moduleName ) && strlen( $moduleName ) <= 255;
 	}
+
+	/**
+	 * Returns LESS compiler set up for use with MediaWiki
+	 *
+	 * @since 1.22
+	 * @return lessc
+	 */
+	public static function getLessCompiler() {
+		global $wgResourceLoaderLESSFunctions, $wgResourceLoaderLESSImportPaths;
+
+		// When called from the installer, it is possible that a required PHP extension
+		// is missing (at least for now; see bug 47564). If this is the case, throw an
+		// exception (caught by the installer) to prevent a fatal error later on.
+		if ( !function_exists( 'ctype_digit' ) ) {
+			throw new MWException( 'lessc requires the Ctype extension' );
+		}
+
+		$less = new lessc();
+		$less->setPreserveComments( true );
+		$less->setVariables( self::getLESSVars() );
+		$less->setImportDir( $wgResourceLoaderLESSImportPaths );
+		foreach ( $wgResourceLoaderLESSFunctions as $name => $func ) {
+			$less->registerFunction( $name, $func );
+		}
+		return $less;
+	}
+
+	/**
+	 * Get global LESS variables.
+	 *
+	 * $since 1.22
+	 * @return array: Map of variable names to string CSS values.
+	 */
+	public static function getLESSVars() {
+		global $wgResourceLoaderLESSVars;
+
+		static $lessVars = null;
+		if ( $lessVars === null ) {
+			$lessVars = $wgResourceLoaderLESSVars;
+			// Sort by key to ensure consistent hashing for cache lookups.
+			ksort( $lessVars );
+		}
+		return $lessVars;
+	}
 }