Update to MediaWiki 1.26.0

22 files changed, 1424 insertions, 847 deletions

diff --git a/includes/resourceloader/DerivativeResourceLoaderContext.php b/includes/resourceloader/DerivativeResourceLoaderContext.php
index 5784f2a0..59675372 100644
--- a/includes/resourceloader/DerivativeResourceLoaderContext.php
+++ b/includes/resourceloader/DerivativeResourceLoaderContext.php
@@ -28,32 +28,32 @@
  * @since 1.24
  */
 class DerivativeResourceLoaderContext extends ResourceLoaderContext {
+	const INHERIT_VALUE = -1;
 
 	/**
 	 * @var ResourceLoaderContext
 	 */
 	private $context;
-	protected $modules;
-	protected $language;
-	protected $direction;
-	protected $skin;
-	protected $user;
-	protected $debug;
-	protected $only;
-	protected $version;
-	protected $hash;
-	protected $raw;
+
+	protected $modules = self::INHERIT_VALUE;
+	protected $language = self::INHERIT_VALUE;
+	protected $direction = self::INHERIT_VALUE;
+	protected $skin = self::INHERIT_VALUE;
+	protected $user = self::INHERIT_VALUE;
+	protected $debug = self::INHERIT_VALUE;
+	protected $only = self::INHERIT_VALUE;
+	protected $version = self::INHERIT_VALUE;
+	protected $raw = self::INHERIT_VALUE;
 
 	public function __construct( ResourceLoaderContext $context ) {
 		$this->context = $context;
 	}
 
 	public function getModules() {
-		if ( !is_null( $this->modules ) ) {
-			return $this->modules;
-		} else {
+		if ( $this->modules === self::INHERIT_VALUE ) {
 			return $this->context->getModules();
 		}
+		return $this->modules;
 	}
 
 	/**
@@ -64,11 +64,10 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getLanguage() {
-		if ( !is_null( $this->language ) ) {
-			return $this->language;
-		} else {
+		if ( $this->language === self::INHERIT_VALUE ) {
 			return $this->context->getLanguage();
 		}
+		return $this->language;
 	}
 
 	/**
@@ -76,16 +75,19 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	 */
 	public function setLanguage( $language ) {
 		$this->language = $language;
-		$this->direction = null; // Invalidate direction since it might be based on language
+		// Invalidate direction since it is based on language
+		$this->direction = null;
 		$this->hash = null;
 	}
 
 	public function getDirection() {
-		if ( !is_null( $this->direction ) ) {
-			return $this->direction;
-		} else {
+		if ( $this->direction === self::INHERIT_VALUE ) {
 			return $this->context->getDirection();
 		}
+		if ( $this->direction === null ) {
+			$this->direction = Language::factory( $this->getLanguage() )->getDir();
+		}
+		return $this->direction;
 	}
 
 	/**
@@ -97,11 +99,10 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getSkin() {
-		if ( !is_null( $this->skin ) ) {
-			return $this->skin;
-		} else {
+		if ( $this->skin === self::INHERIT_VALUE ) {
 			return $this->context->getSkin();
 		}
+		return $this->skin;
 	}
 
 	/**
@@ -113,11 +114,10 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getUser() {
-		if ( !is_null( $this->user ) ) {
-			return $this->user;
-		} else {
+		if ( $this->user === self::INHERIT_VALUE ) {
 			return $this->context->getUser();
 		}
+		return $this->user;
 	}
 
 	/**
@@ -130,11 +130,10 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getDebug() {
-		if ( !is_null( $this->debug ) ) {
-			return $this->debug;
-		} else {
+		if ( $this->debug === self::INHERIT_VALUE ) {
 			return $this->context->getDebug();
 		}
+		return $this->debug;
 	}
 
 	/**
@@ -146,15 +145,14 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getOnly() {
-		if ( !is_null( $this->only ) ) {
-			return $this->only;
-		} else {
+		if ( $this->only === self::INHERIT_VALUE ) {
 			return $this->context->getOnly();
 		}
+		return $this->only;
 	}
 
 	/**
-	 * @param string $only
+	 * @param string|null $only
 	 */
 	public function setOnly( $only ) {
 		$this->only = $only;
@@ -162,15 +160,14 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getVersion() {
-		if ( !is_null( $this->version ) ) {
-			return $this->version;
-		} else {
+		if ( $this->version === self::INHERIT_VALUE ) {
 			return $this->context->getVersion();
 		}
+		return $this->version;
 	}
 
 	/**
-	 * @param string $version
+	 * @param string|null $version
 	 */
 	public function setVersion( $version ) {
 		$this->version = $version;
@@ -178,11 +175,10 @@ class DerivativeResourceLoaderContext extends ResourceLoaderContext {
 	}
 
 	public function getRaw() {
-		if ( !is_null( $this->raw ) ) {
-			return $this->raw;
-		} else {
+		if ( $this->raw === self::INHERIT_VALUE ) {
 			return $this->context->getRaw();
 		}
+		return $this->raw;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoader.php b/includes/resourceloader/ResourceLoader.php
index 150ccd07..c8ece147 100644
--- a/includes/resourceloader/ResourceLoader.php
+++ b/includes/resourceloader/ResourceLoader.php
@@ -22,13 +22,18 @@
  * @author Trevor Parscal
  */
 
+use Psr\Log\LoggerAwareInterface;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use WrappedString\WrappedString;
+
 /**
  * Dynamic JavaScript and CSS resource loading system.
  *
  * Most of the documentation is on the MediaWiki documentation wiki starting at:
  *    https://www.mediawiki.org/wiki/ResourceLoader
  */
-class ResourceLoader {
+class ResourceLoader implements LoggerAwareInterface {
 	/** @var int */
 	protected static $filterCacheVersion = 7;
 
@@ -78,6 +83,11 @@ class ResourceLoader {
 	protected $blobStore;
 
 	/**
+	 * @var LoggerInterface
+	 */
+	private $logger;
+
+	/**
 	 * Load information stored in the database about modules.
 	 *
 	 * This method grabs modules dependencies from the database and updates modules
@@ -169,74 +179,98 @@ class ResourceLoader {
 	 *
 	 * @param string $filter Name of filter to run
 	 * @param string $data Text to filter, such as JavaScript or CSS text
-	 * @param string $cacheReport Whether to include the cache key report
+	 * @param array $options For back-compat, can also be the boolean value for "cacheReport". Keys:
+	 *  - (bool) cache: Whether to allow caching this data. Default: true.
+	 *  - (bool) cacheReport: Whether to include the "cache key" report comment. Default: false.
 	 * @return string Filtered data, or a comment containing an error message
 	 */
-	public function filter( $filter, $data, $cacheReport = true ) {
+	public function filter( $filter, $data, $options = array() ) {
+		// Back-compat
+		if ( is_bool( $options ) ) {
+			$options = array( 'cacheReport' => $options );
+		}
+		// Defaults
+		$options += array( 'cache' => true, 'cacheReport' => false );
+		$stats = RequestContext::getMain()->getStats();
 
-		// For empty/whitespace-only data or for unknown filters, don't perform
-		// any caching or processing
-		if ( trim( $data ) === '' || !in_array( $filter, array( 'minify-js', 'minify-css' ) ) ) {
+		// Don't filter empty content
+		if ( trim( $data ) === '' ) {
 			return $data;
 		}
 
-		// Try for cache hit
-		// Use CACHE_ANYTHING since filtering is very slow compared to DB queries
-		$key = wfMemcKey( 'resourceloader', 'filter', $filter, self::$filterCacheVersion, md5( $data ) );
-		$cache = wfGetCache( CACHE_ANYTHING );
-		$cacheEntry = $cache->get( $key );
-		if ( is_string( $cacheEntry ) ) {
-			wfIncrStats( "rl-$filter-cache-hits" );
-			return $cacheEntry;
+		if ( !in_array( $filter, array( 'minify-js', 'minify-css' ) ) ) {
+			$this->logger->warning( 'Invalid filter {filter}', array(
+				'filter' => $filter
+			) );
+			return $data;
 		}
 
-		$result = '';
-		// Run the filter - we've already verified one of these will work
-		try {
-			wfIncrStats( "rl-$filter-cache-misses" );
-			switch ( $filter ) {
-				case 'minify-js':
-					$result = JavaScriptMinifier::minify( $data,
-						$this->config->get( 'ResourceLoaderMinifierStatementsOnOwnLine' ),
-						$this->config->get( 'ResourceLoaderMinifierMaxLineLength' )
-					);
-					if ( $cacheReport ) {
-						$result .= "\n/* cache key: $key */";
-					}
-					break;
-				case 'minify-css':
-					$result = CSSMin::minify( $data );
-					if ( $cacheReport ) {
-						$result .= "\n/* cache key: $key */";
-					}
-					break;
+		if ( !$options['cache'] ) {
+			$result = self::applyFilter( $filter, $data, $this->config );
+		} else {
+			$key = wfGlobalCacheKey( 'resourceloader', 'filter', $filter, self::$filterCacheVersion, md5( $data ) );
+			$cache = ObjectCache::newAccelerator( CACHE_ANYTHING );
+			$cacheEntry = $cache->get( $key );
+			if ( is_string( $cacheEntry ) ) {
+				$stats->increment( "resourceloader_cache.$filter.hit" );
+				return $cacheEntry;
+			}
+			$result = '';
+			try {
+				$statStart = microtime( true );
+				$result = self::applyFilter( $filter, $data, $this->config );
+				$statTiming = microtime( true ) - $statStart;
+				$stats->increment( "resourceloader_cache.$filter.miss" );
+				$stats->timing( "resourceloader_cache.$filter.timing", 1000 * $statTiming );
+				if ( $options['cacheReport'] ) {
+					$result .= "\n/* cache key: $key */";
+				}
+				// Set a TTL since HHVM's APC doesn't have any limitation or eviction logic.
+				$cache->set( $key, $result, 24 * 3600 );
+			} catch ( Exception $e ) {
+				MWExceptionHandler::logException( $e );
+				$this->logger->warning( 'Minification failed: {exception}', array(
+					'exception' => $e
+				) );
+				$this->errors[] = self::formatExceptionNoComment( $e );
 			}
-
-			// Save filtered text to Memcached
-			$cache->set( $key, $result );
-		} catch ( Exception $e ) {
-			MWExceptionHandler::logException( $e );
-			wfDebugLog( 'resourceloader', __METHOD__ . ": minification failed: $e" );
-			$this->errors[] = self::formatExceptionNoComment( $e );
 		}
 
 		return $result;
 	}
 
+	private static function applyFilter( $filter, $data, Config $config ) {
+		switch ( $filter ) {
+			case 'minify-js':
+				return JavaScriptMinifier::minify( $data,
+					$config->get( 'ResourceLoaderMinifierStatementsOnOwnLine' ),
+					$config->get( 'ResourceLoaderMinifierMaxLineLength' )
+				);
+			case 'minify-css':
+				return CSSMin::minify( $data );
+		}
+
+		return $data;
+	}
+
 	/* Methods */
 
 	/**
 	 * Register core modules and runs registration hooks.
 	 * @param Config|null $config
 	 */
-	public function __construct( Config $config = null ) {
+	public function __construct( Config $config = null, LoggerInterface $logger = null ) {
 		global $IP;
 
-		if ( $config === null ) {
-			wfDebug( __METHOD__ . ' was called without providing a Config instance' );
-			$config = ConfigFactory::getDefaultInstance()->makeConfig( 'main' );
+		if ( !$logger ) {
+			$logger = new NullLogger();
 		}
+		$this->setLogger( $logger );
 
+		if ( !$config ) {
+			$this->logger->debug( __METHOD__ . ' was called without providing a Config instance' );
+			$config = ConfigFactory::getDefaultInstance()->makeConfig( 'main' );
+		}
 		$this->config = $config;
 
 		// Add 'local' source first
@@ -247,9 +281,10 @@ class ResourceLoader {
 
 		// Register core modules
 		$this->register( include "$IP/resources/Resources.php" );
+		$this->register( include "$IP/resources/ResourcesOOUI.php" );
 		// Register extension modules
-		Hooks::run( 'ResourceLoaderRegisterModules', array( &$this ) );
 		$this->register( $config->get( 'ResourceModules' ) );
+		Hooks::run( 'ResourceLoaderRegisterModules', array( &$this ) );
 
 		if ( $config->get( 'EnableJavaScriptTest' ) === true ) {
 			$this->registerTestModules();
@@ -265,9 +300,21 @@ class ResourceLoader {
 		return $this->config;
 	}
 
+	public function setLogger( LoggerInterface $logger ) {
+		$this->logger = $logger;
+	}
+
+	/**
+	 * @since 1.26
+	 * @return MessageBlobStore
+	 */
+	public function getMessageBlobStore() {
+		return $this->blobStore;
+	}
+
 	/**
-	 * @param MessageBlobStore $blobStore
 	 * @since 1.25
+	 * @param MessageBlobStore $blobStore
 	 */
 	public function setMessageBlobStore( MessageBlobStore $blobStore ) {
 		$this->blobStore = $blobStore;
@@ -566,19 +613,44 @@ class ResourceLoader {
 	}
 
 	/**
+	 * @since 1.26
+	 * @param string $value
+	 * @return string Hash
+	 */
+	public static function makeHash( $value ) {
+		// Use base64 to output more entropy in a more compact string (default hex is only base16).
+		// The first 8 chars of a base64 encoded digest represent the same binary as
+		// the first 12 chars of a hex encoded digest.
+		return substr( base64_encode( sha1( $value, true ) ), 0, 8 );
+	}
+
+	/**
+	 * Helper method to get and combine versions of multiple modules.
+	 *
+	 * @since 1.26
+	 * @param ResourceLoaderContext $context
+	 * @param array $modules List of ResourceLoaderModule objects
+	 * @return string Hash
+	 */
+	public function getCombinedVersion( ResourceLoaderContext $context, Array $modules ) {
+		if ( !$modules ) {
+			return '';
+		}
+		// Support: PHP 5.3 ("$this" for anonymous functions was added in PHP 5.4.0)
+		// http://php.net/functions.anonymous
+		$rl = $this;
+		$hashes = array_map( function ( $module ) use ( $rl, $context ) {
+			return $rl->getModule( $module )->getVersionHash( $context );
+		}, $modules );
+		return self::makeHash( implode( $hashes ) );
+	}
+
+	/**
 	 * Output a response to a load request, including the content-type header.
 	 *
 	 * @param ResourceLoaderContext $context Context in which a response should be formed
 	 */
 	public function respond( ResourceLoaderContext $context ) {
-		// Use file cache if enabled and available...
-		if ( $this->config->get( 'UseFileCache' ) ) {
-			$fileCache = ResourceFileCache::newFromContext( $context );
-			if ( $this->tryRespondFromFileCache( $fileCache, $context ) ) {
-				return; // output handled
-			}
-		}
-
 		// Buffer output to catch warnings. Normally we'd use ob_clean() on the
 		// top-level output buffer to clear warnings, but that breaks when ob_gzhandler
 		// is used: ob_clean() will clear the GZIP header in that case and it won't come
@@ -597,7 +669,7 @@ class ResourceLoader {
 				// Do not allow private modules to be loaded from the web.
 				// This is a security issue, see bug 34907.
 				if ( $module->getGroup() === 'private' ) {
-					wfDebugLog( 'resourceloader', __METHOD__ . ": request for private module '$name' denied" );
+					$this->logger->debug( "Request for private module '$name' denied" );
 					$this->errors[] = "Cannot show private module \"$name\"";
 					continue;
 				}
@@ -607,37 +679,46 @@ class ResourceLoader {
 			}
 		}
 
-		// Preload information needed to the mtime calculation below
 		try {
+			// Preload for getCombinedVersion()
 			$this->preloadModuleInfo( array_keys( $modules ), $context );
 		} catch ( Exception $e ) {
 			MWExceptionHandler::logException( $e );
-			wfDebugLog( 'resourceloader', __METHOD__ . ": preloading module info failed: $e" );
+			$this->logger->warning( 'Preloading module info failed: {exception}', array(
+				'exception' => $e
+			) );
 			$this->errors[] = self::formatExceptionNoComment( $e );
 		}
 
-		// To send Last-Modified and support If-Modified-Since, we need to detect
-		// the last modified time
-		$mtime = wfTimestamp( TS_UNIX, $this->config->get( 'CacheEpoch' ) );
-		foreach ( $modules as $module ) {
-			/**
-			 * @var $module ResourceLoaderModule
-			 */
-			try {
-				// Calculate maximum modified time
-				$mtime = max( $mtime, $module->getModifiedTime( $context ) );
-			} catch ( Exception $e ) {
-				MWExceptionHandler::logException( $e );
-				wfDebugLog( 'resourceloader', __METHOD__ . ": calculating maximum modified time failed: $e" );
-				$this->errors[] = self::formatExceptionNoComment( $e );
-			}
+		// Combine versions to propagate cache invalidation
+		$versionHash = '';
+		try {
+			$versionHash = $this->getCombinedVersion( $context, array_keys( $modules ) );
+		} catch ( Exception $e ) {
+			MWExceptionHandler::logException( $e );
+			$this->logger->warning( 'Calculating version hash failed: {exception}', array(
+				'exception' => $e
+			) );
+			$this->errors[] = self::formatExceptionNoComment( $e );
 		}
 
-		// If there's an If-Modified-Since header, respond with a 304 appropriately
-		if ( $this->tryRespondLastModified( $context, $mtime ) ) {
+		// See RFC 2616 § 3.11 Entity Tags
+		// http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.11
+		$etag = 'W/"' . $versionHash . '"';
+
+		// Try the client-side cache first
+		if ( $this->tryRespondNotModified( $context, $etag ) ) {
 			return; // output handled (buffers cleared)
 		}
 
+		// Use file cache if enabled and available...
+		if ( $this->config->get( 'UseFileCache' ) ) {
+			$fileCache = ResourceFileCache::newFromContext( $context );
+			if ( $this->tryRespondFromFileCache( $fileCache, $context, $etag ) ) {
+				return; // output handled
+			}
+		}
+
 		// Generate a response
 		$response = $this->makeModuleResponse( $context, $modules, $missing );
 
@@ -659,26 +740,25 @@ class ResourceLoader {
 			}
 		}
 
-		// Send content type and cache related headers
-		$this->sendResponseHeaders( $context, $mtime, (bool)$this->errors );
+		$this->sendResponseHeaders( $context, $etag, (bool)$this->errors );
 
 		// Remove the output buffer and output the response
 		ob_end_clean();
 
 		if ( $context->getImageObj() && $this->errors ) {
 			// We can't show both the error messages and the response when it's an image.
-			$errorText = '';
-			foreach ( $this->errors as $error ) {
-				$errorText .= $error . "\n";
-			}
-			$response = $errorText;
+			$response = implode( "\n\n",  $this->errors );
 		} elseif ( $this->errors ) {
-			// Prepend comments indicating errors
-			$errorText = '';
-			foreach ( $this->errors as $error ) {
-				$errorText .= self::makeComment( $error );
+			$errorText = implode( "\n\n", $this->errors );
+			$errorResponse = self::makeComment( $errorText );
+			if ( $context->shouldIncludeScripts() ) {
+				$errorResponse .= 'if (window.console && console.error) {'
+					. Xml::encodeJsCall( 'console.error', array( $errorText ) )
+					. "}\n";
 			}
-			$response = $errorText . $response;
+
+			// Prepend error info to the response
+			$response = $errorResponse . $response;
 		}
 
 		$this->errors = array();
@@ -687,13 +767,16 @@ class ResourceLoader {
 	}
 
 	/**
-	 * Send content type and last modified headers to the client.
+	 * Send main response headers to the client.
+	 *
+	 * Deals with Content-Type, CORS (for stylesheets), and caching.
+	 *
 	 * @param ResourceLoaderContext $context
-	 * @param string $mtime TS_MW timestamp to use for last-modified
+	 * @param string $etag ETag header value
 	 * @param bool $errors Whether there are errors in the response
 	 * @return void
 	 */
-	protected function sendResponseHeaders( ResourceLoaderContext $context, $mtime, $errors ) {
+	protected function sendResponseHeaders( ResourceLoaderContext $context, $etag, $errors ) {
 		$rlMaxage = $this->config->get( 'ResourceLoaderMaxage' );
 		// If a version wasn't specified we need a shorter expiry time for updates
 		// to propagate to clients quickly
@@ -720,7 +803,9 @@ class ResourceLoader {
 		} else {
 			header( 'Content-Type: text/javascript; charset=utf-8' );
 		}
-		header( 'Last-Modified: ' . wfTimestamp( TS_RFC2822, $mtime ) );
+		// See RFC 2616 § 14.19 ETag
+		// http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.19
+		header( 'ETag: ' . $etag );
 		if ( $context->getDebug() ) {
 			// Do not cache debug responses
 			header( 'Cache-Control: private, no-cache, must-revalidate' );
@@ -733,39 +818,36 @@ class ResourceLoader {
 	}
 
 	/**
-	 * Respond with 304 Last Modified if appropiate.
+	 * Respond with HTTP 304 Not Modified if appropiate.
 	 *
-	 * If there's an If-Modified-Since header, respond with a 304 appropriately
+	 * If there's an If-None-Match header, respond with a 304 appropriately
 	 * and clear out the output buffer. If the client cache is too old then do nothing.
 	 *
 	 * @param ResourceLoaderContext $context
-	 * @param string $mtime The TS_MW timestamp to check the header against
-	 * @return bool True if 304 header sent and output handled
+	 * @param string $etag ETag header value
+	 * @return bool True if HTTP 304 was sent and output handled
 	 */
-	protected function tryRespondLastModified( ResourceLoaderContext $context, $mtime ) {
-		// If there's an If-Modified-Since header, respond with a 304 appropriately
-		// Some clients send "timestamp;length=123". Strip the part after the first ';'
-		// so we get a valid timestamp.
-		$ims = $context->getRequest()->getHeader( 'If-Modified-Since' );
+	protected function tryRespondNotModified( ResourceLoaderContext $context, $etag ) {
+		// See RFC 2616 § 14.26 If-None-Match
+		// http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26
+		$clientKeys = $context->getRequest()->getHeader( 'If-None-Match', WebRequest::GETHEADER_LIST );
 		// Never send 304s in debug mode
-		if ( $ims !== false && !$context->getDebug() ) {
-			$imsTS = strtok( $ims, ';' );
-			if ( $mtime <= wfTimestamp( TS_UNIX, $imsTS ) ) {
-				// There's another bug in ob_gzhandler (see also the comment at
-				// the top of this function) that causes it to gzip even empty
-				// responses, meaning it's impossible to produce a truly empty
-				// response (because the gzip header is always there). This is
-				// a problem because 304 responses have to be completely empty
-				// per the HTTP spec, and Firefox behaves buggily when they're not.
-				// See also http://bugs.php.net/bug.php?id=51579
-				// To work around this, we tear down all output buffering before
-				// sending the 304.
-				wfResetOutputBuffers( /* $resetGzipEncoding = */ true );
-
-				header( 'HTTP/1.0 304 Not Modified' );
-				header( 'Status: 304 Not Modified' );
-				return true;
-			}
+		if ( $clientKeys !== false && !$context->getDebug() && in_array( $etag, $clientKeys ) ) {
+			// There's another bug in ob_gzhandler (see also the comment at
+			// the top of this function) that causes it to gzip even empty
+			// responses, meaning it's impossible to produce a truly empty
+			// response (because the gzip header is always there). This is
+			// a problem because 304 responses have to be completely empty
+			// per the HTTP spec, and Firefox behaves buggily when they're not.
+			// See also http://bugs.php.net/bug.php?id=51579
+			// To work around this, we tear down all output buffering before
+			// sending the 304.
+			wfResetOutputBuffers( /* $resetGzipEncoding = */ true );
+
+			HttpStatus::header( 304 );
+
+			$this->sendResponseHeaders( $context, $etag, false );
+			return true;
 		}
 		return false;
 	}
@@ -775,10 +857,13 @@ class ResourceLoader {
 	 *
 	 * @param ResourceFileCache $fileCache Cache object for this request URL
 	 * @param ResourceLoaderContext $context Context in which to generate a response
+	 * @param string $etag ETag header value
 	 * @return bool If this found a cache file and handled the response
 	 */
 	protected function tryRespondFromFileCache(
-		ResourceFileCache $fileCache, ResourceLoaderContext $context
+		ResourceFileCache $fileCache,
+		ResourceLoaderContext $context,
+		$etag
 	) {
 		$rlMaxage = $this->config->get( 'ResourceLoaderMaxage' );
 		// Buffer output to catch warnings.
@@ -799,16 +884,12 @@ class ResourceLoader {
 		if ( $good ) {
 			$ts = $fileCache->cacheTimestamp();
 			// Send content type and cache headers
-			$this->sendResponseHeaders( $context, $ts, false );
-			// If there's an If-Modified-Since header, respond with a 304 appropriately
-			if ( $this->tryRespondLastModified( $context, $ts ) ) {
-				return false; // output handled (buffers cleared)
-			}
+			$this->sendResponseHeaders( $context, $etag, false );
 			$response = $fileCache->fetchText();
 			// 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() ) ) {
-				$response = "/*\n$warnings\n*/\n" . $response;
+				$response = self::makeComment( $warnings ) . $response;
 			}
 			// Remove the output buffer and output the response
 			ob_end_clean();
@@ -854,11 +935,11 @@ class ResourceLoader {
 	protected static function formatExceptionNoComment( $e ) {
 		global $wgShowExceptionDetails;
 
-		if ( $wgShowExceptionDetails ) {
-			return $e->__toString();
-		} else {
-			return wfMessage( 'internalerror' )->text();
+		if ( !$wgShowExceptionDetails ) {
+			return 'Internal error';
 		}
+
+		return $e->__toString();
 	}
 
 	/**
@@ -896,17 +977,14 @@ MESSAGE;
 		// Pre-fetch blobs
 		if ( $context->shouldIncludeMessages() ) {
 			try {
-				$blobs = $this->blobStore->get( $this, $modules, $context->getLanguage() );
+				$this->blobStore->get( $this, $modules, $context->getLanguage() );
 			} catch ( Exception $e ) {
 				MWExceptionHandler::logException( $e );
-				wfDebugLog(
-					'resourceloader',
-					__METHOD__ . ": pre-fetching blobs from MessageBlobStore failed: $e"
-				);
+				$this->logger->warning( 'Prefetching MessageBlobStore failed: {exception}', array(
+					'exception' => $e
+				) );
 				$this->errors[] = self::formatExceptionNoComment( $e );
 			}
-		} else {
-			$blobs = array();
 		}
 
 		foreach ( $missing as $name ) {
@@ -916,116 +994,43 @@ MESSAGE;
 		// Generate output
 		$isRaw = false;
 		foreach ( $modules as $name => $module ) {
-			/**
-			 * @var $module ResourceLoaderModule
-			 */
-
 			try {
-				$scripts = '';
-				if ( $context->shouldIncludeScripts() ) {
-					// If we are in debug mode, we'll want to return an array of URLs if possible
-					// However, we can't do this if the module doesn't support it
-					// We also can't do this if there is an only= parameter, because we have to give
-					// the module a way to return a load.php URL without causing an infinite loop
-					if ( $context->getDebug() && !$context->getOnly() && $module->supportsURLLoading() ) {
-						$scripts = $module->getScriptURLsForDebug( $context );
-					} else {
-						$scripts = $module->getScript( $context );
-						// rtrim() because there are usually a few line breaks
-						// after the last ';'. A new line at EOF, a new line
-						// added by ResourceLoaderFileModule::readScriptFiles, etc.
-						if ( is_string( $scripts )
-							&& strlen( $scripts )
-							&& substr( rtrim( $scripts ), -1 ) !== ';'
-						) {
-							// Append semicolon to prevent weird bugs caused by files not
-							// terminating their statements right (bug 27054)
-							$scripts .= ";\n";
-						}
-					}
-				}
-				// Styles
-				$styles = array();
-				if ( $context->shouldIncludeStyles() ) {
-					// Don't create empty stylesheets like array( '' => '' ) for modules
-					// that don't *have* any stylesheets (bug 38024).
-					$stylePairs = $module->getStyles( $context );
-					if ( count( $stylePairs ) ) {
-						// If we are in debug mode without &only= set, we'll want to return an array of URLs
-						// See comment near shouldIncludeScripts() for more details
-						if ( $context->getDebug() && !$context->getOnly() && $module->supportsURLLoading() ) {
-							$styles = array(
-								'url' => $module->getStyleURLsForDebug( $context )
-							);
-						} else {
-							// Minify CSS before embedding in mw.loader.implement call
-							// (unless in debug mode)
-							if ( !$context->getDebug() ) {
-								foreach ( $stylePairs as $media => $style ) {
-									// Can be either a string or an array of strings.
-									if ( is_array( $style ) ) {
-										$stylePairs[$media] = array();
-										foreach ( $style as $cssText ) {
-											if ( is_string( $cssText ) ) {
-												$stylePairs[$media][] = $this->filter( 'minify-css', $cssText );
-											}
-										}
-									} elseif ( is_string( $style ) ) {
-										$stylePairs[$media] = $this->filter( 'minify-css', $style );
-									}
-								}
-							}
-							// Wrap styles into @media groups as needed and flatten into a numerical array
-							$styles = array(
-								'css' => self::makeCombinedStyles( $stylePairs )
-							);
-						}
-					}
-				}
-
-				// Messages
-				$messagesBlob = isset( $blobs[$name] ) ? $blobs[$name] : '{}';
+				$content = $module->getModuleContent( $context );
 
 				// Append output
 				switch ( $context->getOnly() ) {
 					case 'scripts':
+						$scripts = $content['scripts'];
 						if ( is_string( $scripts ) ) {
 							// Load scripts raw...
 							$out .= $scripts;
 						} elseif ( is_array( $scripts ) ) {
 							// ...except when $scripts is an array of URLs
-							$out .= self::makeLoaderImplementScript( $name, $scripts, array(), array() );
+							$out .= self::makeLoaderImplementScript( $name, $scripts, array(), array(), array() );
 						}
 						break;
 					case 'styles':
+						$styles = $content['styles'];
 						// We no longer seperate into media, they are all combined now with
 						// custom media type groups into @media .. {} sections as part of the css string.
 						// Module returns either an empty array or a numerical array with css strings.
 						$out .= isset( $styles['css'] ) ? implode( '', $styles['css'] ) : '';
 						break;
-					case 'messages':
-						$out .= self::makeMessageSetScript( new XmlJsCode( $messagesBlob ) );
-						break;
-					case 'templates':
-						$out .= Xml::encodeJsCall(
-							'mw.templates.set',
-							array( $name, (object)$module->getTemplates() ),
-							ResourceLoader::inDebugMode()
-						);
-						break;
 					default:
 						$out .= self::makeLoaderImplementScript(
 							$name,
-							$scripts,
-							$styles,
-							new XmlJsCode( $messagesBlob ),
-							$module->getTemplates()
+							isset( $content['scripts'] ) ? $content['scripts'] : '',
+							isset( $content['styles'] ) ? $content['styles'] : array(),
+							isset( $content['messagesBlob'] ) ? new XmlJsCode( $content['messagesBlob'] ) : array(),
+							isset( $content['templates'] ) ? $content['templates'] : array()
 						);
 						break;
 				}
 			} catch ( Exception $e ) {
 				MWExceptionHandler::logException( $e );
-				wfDebugLog( 'resourceloader', __METHOD__ . ": generating module package failed: $e" );
+				$this->logger->warning( 'Generating module package failed: {exception}', array(
+					'exception' => $e
+				) );
 				$this->errors[] = self::formatExceptionNoComment( $e );
 
 				// Respond to client with error-state instead of module implementation
@@ -1056,11 +1061,19 @@ MESSAGE;
 			}
 		}
 
+		$enableFilterCache = true;
+		if ( count( $modules ) === 1 && reset( $modules ) instanceof ResourceLoaderUserTokensModule ) {
+			// If we're building the embedded user.tokens, don't cache (T84960)
+			$enableFilterCache = false;
+		}
+
 		if ( !$context->getDebug() ) {
 			if ( $context->getOnly() === 'styles' ) {
 				$out = $this->filter( 'minify-css', $out );
 			} else {
-				$out = $this->filter( 'minify-js', $out );
+				$out = $this->filter( 'minify-js', $out, array(
+					'cache' => $enableFilterCache
+				) );
 			}
 		}
 
@@ -1084,11 +1097,22 @@ MESSAGE;
 	 * @throws MWException
 	 * @return string
 	 */
-	public static function makeLoaderImplementScript( $name, $scripts, $styles,
-		$messages, $templates
+	public static function makeLoaderImplementScript(
+		$name, $scripts, $styles, $messages, $templates
 	) {
 		if ( is_string( $scripts ) ) {
-			$scripts = new XmlJsCode( "function ( $, jQuery ) {\n{$scripts}\n}" );
+			// Site and user module are a legacy scripts that run in the global scope (no closure).
+			// Transportation as string instructs mw.loader.implement to use globalEval.
+			if ( $name === 'site' || $name === 'user' ) {
+				// Minify manually because the general makeModuleResponse() minification won't be
+				// effective here due to the script being a string instead of a function. (T107377)
+				if ( !ResourceLoader::inDebugMode() ) {
+					$scripts = self::applyFilter( 'minify-js', $scripts,
+						ConfigFactory::getDefaultInstance()->makeConfig( 'main' ) );
+				}
+			} else {
+				$scripts = new XmlJsCode( "function ( $, jQuery ) {\n{$scripts}\n}" );
+			}
 		} elseif ( !is_array( $scripts ) ) {
 			throw new MWException( 'Invalid scripts error. Array of URLs or string of code expected.' );
 		}
@@ -1098,9 +1122,9 @@ MESSAGE;
 		$module = array(
 			$name,
 			$scripts,
-			(object) $styles,
-			(object) $messages,
-			(object) $templates,
+			(object)$styles,
+			(object)$messages,
+			(object)$templates,
 		);
 		self::trimArray( $module );
 
@@ -1193,7 +1217,7 @@ MESSAGE;
 	 * and $group as supplied.
 	 *
 	 * @param string $name Module name
-	 * @param int $version Module version number as a timestamp
+	 * @param string $version Module version hash
 	 * @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.
@@ -1265,7 +1289,7 @@ MESSAGE;
 	 *        Registers modules with the given names and parameters.
 	 *
 	 * @param string $name Module name
-	 * @param int $version Module version number as a timestamp
+	 * @param string $version Module version hash
 	 * @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
@@ -1346,11 +1370,30 @@ MESSAGE;
 	 * Returns JS code which runs given JS code if the client-side framework is
 	 * present.
 	 *
+	 * @deprecated since 1.25; use makeInlineScript instead
 	 * @param string $script JavaScript code
 	 * @return string
 	 */
 	public static function makeLoaderConditionalScript( $script ) {
-		return "if(window.mw){\n" . trim( $script ) . "\n}";
+		return "window.RLQ = window.RLQ || []; window.RLQ.push( function () {\n" . trim( $script ) . "\n} );";
+	}
+
+	/**
+	 * Construct an inline script tag with given JS code.
+	 *
+	 * The code will be wrapped in a closure, and it will be executed by ResourceLoader
+	 * only if the client has adequate support for MediaWiki JavaScript code.
+	 *
+	 * @param string $script JavaScript code
+	 * @return WrappedString HTML
+	 */
+	public static function makeInlineScript( $script ) {
+		$js = self::makeLoaderConditionalScript( $script );
+		return new WrappedString(
+			Html::inlineScript( $js ),
+			"<script>window.RLQ = window.RLQ || []; window.RLQ.push( function () {\n",
+			"\n} );</script>"
+		);
 	}
 
 	/**
@@ -1361,11 +1404,13 @@ MESSAGE;
 	 * @return string
 	 */
 	public static function makeConfigSetScript( array $configuration ) {
-		return Xml::encodeJsCall(
-			'mw.config.set',
-			array( $configuration ),
-			ResourceLoader::inDebugMode()
-		);
+		if ( ResourceLoader::inDebugMode() ) {
+			return Xml::encodeJsCall( 'mw.config.set', array( $configuration ), true );
+		}
+
+		$config = RequestContext::getMain()->getConfig();
+		$js = Xml::encodeJsCall( 'mw.config.set', array( $configuration ), false );
+		return self::applyFilter( 'minify-js', $js, $config );
 	}
 
 	/**
@@ -1427,7 +1472,7 @@ MESSAGE;
 	 * @param string $source Name of the ResourceLoader source
 	 * @param ResourceLoaderContext $context
 	 * @param array $extraQuery
-	 * @return string URL to load.php. May be protocol-relative (if $wgLoadScript is procol-relative)
+	 * @return string URL to load.php. May be protocol-relative if $wgLoadScript is, too.
 	 */
 	public function createLoaderURL( $source, ResourceLoaderContext $context,
 		$extraQuery = array()
@@ -1435,14 +1480,12 @@ MESSAGE;
 		$query = self::createLoaderQuery( $context, $extraQuery );
 		$script = $this->getLoadScript( $source );
 
-		// Prevent the IE6 extension check from being triggered (bug 28840)
-		// by appending a character that's invalid in Windows extensions ('*')
-		return wfExpandUrl( wfAppendQuery( $script, $query ) . '&*', PROTO_RELATIVE );
+		return wfAppendQuery( $script, $query );
 	}
 
 	/**
 	 * Build a load.php URL
-	 * @deprecated since 1.24, use createLoaderURL instead
+	 * @deprecated since 1.24 Use createLoaderURL() instead
 	 * @param array $modules Array of module names (strings)
 	 * @param string $lang Language code
 	 * @param string $skin Skin name
@@ -1453,7 +1496,7 @@ MESSAGE;
 	 * @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)
+	 * @return string URL to load.php. May be protocol-relative if $wgLoadScript is, too.
 	 */
 	public static function makeLoaderURL( $modules, $lang, $skin, $user = null,
 		$version = null, $debug = false, $only = null, $printable = false,
@@ -1465,9 +1508,7 @@ MESSAGE;
 			$only, $printable, $handheld, $extraQuery
 		);
 
-		// Prevent the IE6 extension check from being triggered (bug 28840)
-		// by appending a character that's invalid in Windows extensions ('*')
-		return wfExpandUrl( wfAppendQuery( $wgLoadScript, $query ) . '&*', PROTO_RELATIVE );
+		return wfAppendQuery( $wgLoadScript, $query );
 	}
 
 	/**
@@ -1562,27 +1603,23 @@ MESSAGE;
 	 * @param Config $config
 	 * @throws MWException
 	 * @since 1.22
-	 * @return lessc
+	 * @return Less_Parser
 	 */
 	public static function getLessCompiler( Config $config ) {
 		// 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 ( !class_exists( 'lessc' ) ) {
-			throw new MWException( 'MediaWiki requires the lessphp compiler' );
-		}
-		if ( !function_exists( 'ctype_digit' ) ) {
-			throw new MWException( 'lessc requires the Ctype extension' );
+		if ( !class_exists( 'Less_Parser' ) ) {
+			throw new MWException( 'MediaWiki requires the less.php parser' );
 		}
 
-		$less = new lessc();
-		$less->setPreserveComments( true );
-		$less->setVariables( self::getLessVars( $config ) );
-		$less->setImportDir( $config->get( 'ResourceLoaderLESSImportPaths' ) );
-		foreach ( $config->get( 'ResourceLoaderLESSFunctions' ) as $name => $func ) {
-			$less->registerFunction( $name, $func );
-		}
-		return $less;
+		$parser = new Less_Parser;
+		$parser->ModifyVars( self::getLessVars( $config ) );
+		$parser->SetImportDirs( array_fill_keys( $config->get( 'ResourceLoaderLESSImportPaths' ), '' ) );
+		$parser->SetOption( 'relativeUrls', false );
+		$parser->SetCacheDir( $config->get( 'CacheDirectory' ) ?: wfTempDir() );
+
+		return $parser;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderContext.php b/includes/resourceloader/ResourceLoaderContext.php
index a6a7d347..2e1752a6 100644
--- a/includes/resourceloader/ResourceLoaderContext.php
+++ b/includes/resourceloader/ResourceLoaderContext.php
@@ -22,6 +22,8 @@
  * @author Roan Kattouw
  */
 
+use MediaWiki\Logger\LoggerFactory;
+
 /**
  * Object passed around to modules which contains information about the state
  * of a specific loader request
@@ -57,24 +59,26 @@ class ResourceLoaderContext {
 		$this->resourceLoader = $resourceLoader;
 		$this->request = $request;
 
-		// Interpret request
 		// List of modules
 		$modules = $request->getVal( 'modules' );
 		$this->modules = $modules ? self::expandModuleNames( $modules ) : array();
+
 		// Various parameters
-		$this->skin = $request->getVal( 'skin' );
 		$this->user = $request->getVal( 'user' );
 		$this->debug = $request->getFuzzyBool(
-			'debug', $resourceLoader->getConfig()->get( 'ResourceLoaderDebug' )
+			'debug',
+			$resourceLoader->getConfig()->get( 'ResourceLoaderDebug' )
 		);
-		$this->only = $request->getVal( 'only' );
-		$this->version = $request->getVal( 'version' );
+		$this->only = $request->getVal( 'only', null );
+		$this->version = $request->getVal( 'version', null );
 		$this->raw = $request->getFuzzyBool( 'raw' );
+
 		// Image requests
 		$this->image = $request->getVal( 'image' );
 		$this->variant = $request->getVal( 'variant' );
 		$this->format = $request->getVal( 'format' );
 
+		$this->skin = $request->getVal( 'skin' );
 		$skinnames = Skin::getSkinNames();
 		// If no skin is specified, or we don't recognize the skin, use the default skin
 		if ( !$this->skin || !isset( $skinnames[$this->skin] ) ) {
@@ -123,7 +127,8 @@ class ResourceLoaderContext {
 	 */
 	public static function newDummyContext() {
 		return new self( new ResourceLoader(
-			ConfigFactory::getDefaultInstance()->makeConfig( 'main' )
+			ConfigFactory::getDefaultInstance()->makeConfig( 'main' ),
+			LoggerFactory::getInstance( 'resourceloader' )
 		), new FauxRequest( array() ) );
 	}
 
@@ -154,7 +159,7 @@ class ResourceLoaderContext {
 	public function getLanguage() {
 		if ( $this->language === null ) {
 			// Must be a valid language code after this point (bug 62849)
-			$this->language = RequestContext::sanitizeLangCode( $this->request->getVal( 'lang' ) );
+			$this->language = RequestContext::sanitizeLangCode( $this->getRequest()->getVal( 'lang' ) );
 		}
 		return $this->language;
 	}
@@ -164,7 +169,7 @@ class ResourceLoaderContext {
 	 */
 	public function getDirection() {
 		if ( $this->direction === null ) {
-			$this->direction = $this->request->getVal( 'dir' );
+			$this->direction = $this->getRequest()->getVal( 'dir' );
 			if ( !$this->direction ) {
 				// Determine directionality based on user language (bug 6100)
 				$this->direction = Language::factory( $this->getLanguage() )->getDir();
@@ -174,7 +179,7 @@ class ResourceLoaderContext {
 	}
 
 	/**
-	 * @return string|null
+	 * @return string
 	 */
 	public function getSkin() {
 		return $this->skin;
@@ -227,6 +232,8 @@ class ResourceLoaderContext {
 	}
 
 	/**
+	 * @see ResourceLoaderModule::getVersionHash
+	 * @see OutputPage::makeResourceLoaderLink
 	 * @return string|null
 	 */
 	public function getVersion() {
@@ -285,7 +292,7 @@ class ResourceLoaderContext {
 				return $this->imageObj;
 			}
 
-			$image = $module->getImage( $this->image );
+			$image = $module->getImage( $this->image, $this );
 			if ( !$image ) {
 				return $this->imageObj;
 			}
@@ -300,21 +307,21 @@ class ResourceLoaderContext {
 	 * @return bool
 	 */
 	public function shouldIncludeScripts() {
-		return is_null( $this->getOnly() ) || $this->getOnly() === 'scripts';
+		return $this->getOnly() === null || $this->getOnly() === 'scripts';
 	}
 
 	/**
 	 * @return bool
 	 */
 	public function shouldIncludeStyles() {
-		return is_null( $this->getOnly() ) || $this->getOnly() === 'styles';
+		return $this->getOnly() === null || $this->getOnly() === 'styles';
 	}
 
 	/**
 	 * @return bool
 	 */
 	public function shouldIncludeMessages() {
-		return is_null( $this->getOnly() ) || $this->getOnly() === 'messages';
+		return $this->getOnly() === null;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderEditToolbarModule.php b/includes/resourceloader/ResourceLoaderEditToolbarModule.php
index d79174cd..da729fdc 100644
--- a/includes/resourceloader/ResourceLoaderEditToolbarModule.php
+++ b/includes/resourceloader/ResourceLoaderEditToolbarModule.php
@@ -56,7 +56,7 @@ class ResourceLoaderEditToolbarModule extends ResourceLoaderFileModule {
 		// This is very conveniently formatted and we can pass it right through
 		$vars = $language->getImageFiles();
 
-		// lessc tries to be helpful and parse our variables as LESS source code
+		// less.php tries to be helpful and parse our variables as LESS source code
 		foreach ( $vars as $key => &$value ) {
 			$value = self::cssSerializeString( $value );
 		}
@@ -65,25 +65,10 @@ class ResourceLoaderEditToolbarModule extends ResourceLoaderFileModule {
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
-	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return max(
-			parent::getModifiedTime( $context ),
-			$this->getHashMtime( $context )
-		);
-	}
-
-	/**
-	 * @param ResourceLoaderContext $context
-	 * @return string Hash
+	 * @return bool
 	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return md5(
-			parent::getModifiedHash( $context ) .
-			serialize( $this->getLessVars( $context ) )
-		);
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
@@ -93,11 +78,11 @@ class ResourceLoaderEditToolbarModule extends ResourceLoaderFileModule {
 	 *
 	 * @throws MWException
 	 * @param ResourceLoaderContext $context
-	 * @return lessc
+	 * @return Less_Parser
 	 */
 	protected function getLessCompiler( ResourceLoaderContext $context = null ) {
-		$compiler = parent::getLessCompiler();
-		$compiler->setVariables( $this->getLessVars( $context ) );
-		return $compiler;
+		$parser = parent::getLessCompiler();
+		$parser->ModifyVars( $this->getLessVars( $context ) );
+		return $parser;
 	}
 }
diff --git a/includes/resourceloader/ResourceLoaderFileModule.php b/includes/resourceloader/ResourceLoaderFileModule.php
index 671098e1..7fbc1cb4 100644
--- a/includes/resourceloader/ResourceLoaderFileModule.php
+++ b/includes/resourceloader/ResourceLoaderFileModule.php
@@ -144,15 +144,6 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	protected $hasGeneratedStyles = false;
 
 	/**
-	 * @var array Cache for mtime
-	 * @par Usage:
-	 * @code
-	 * array( [hash] => [mtime], [hash] => [mtime], ... )
-	 * @endcode
-	 */
-	protected $modifiedTime = array();
-
-	/**
 	 * @var array Place where readStyleFile() tracks file dependencies
 	 * @par Usage:
 	 * @code
@@ -161,6 +152,12 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	 */
 	protected $localFileRefs = array();
 
+	/**
+	 * @var array Place where readStyleFile() tracks file dependencies for non-existent files.
+	 * Used in tests to detect missing dependencies.
+	 */
+	protected $missingLocalFileRefs = array();
+
 	/* Methods */
 
 	/**
@@ -281,8 +278,9 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 					$this->{$member} = $option;
 					break;
 				// Single strings
-				case 'group':
 				case 'position':
+					$this->isPositionDefined = true;
+				case 'group':
 				case 'skipFunction':
 					$this->{$member} = (string)$option;
 					break;
@@ -486,10 +484,10 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 
 	/**
 	 * Gets list of names of modules this module depends on.
-	 *
+	 * @param ResourceLoaderContext context
 	 * @return array List of module names
 	 */
-	public function getDependencies() {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
 		return $this->dependencies;
 	}
 
@@ -522,24 +520,28 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * Get the last modified timestamp of this module.
+	 * Disable module content versioning.
 	 *
-	 * Last modified timestamps are calculated from the highest last modified
-	 * timestamp of this module's constituent files as well as the files it
-	 * depends on. This function is context-sensitive, only performing
-	 * calculations on files relevant to the given language, skin and debug
-	 * mode.
+	 * This class uses getDefinitionSummary() instead, to avoid filesystem overhead
+	 * involved with building the full module content inside a startup request.
 	 *
-	 * @param ResourceLoaderContext $context Context in which to calculate
-	 *     the modified time
-	 * @return int UNIX timestamp
-	 * @see ResourceLoaderModule::getFileDependencies
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		if ( isset( $this->modifiedTime[$context->getHash()] ) ) {
-			return $this->modifiedTime[$context->getHash()];
-		}
+	public function enableModuleContentVersion() {
+		return false;
+	}
 
+	/**
+	 * Helper method to gather file hashes for getDefinitionSummary.
+	 *
+	 * This function is context-sensitive, only computing hashes of files relevant to the
+	 * given language, skin, etc.
+	 *
+	 * @see ResourceLoaderModule::getFileDependencies
+	 * @param ResourceLoaderContext $context
+	 * @return array
+	 */
+	protected function getFileHashes( ResourceLoaderContext $context ) {
 		$files = array();
 
 		// Flatten style files into $files
@@ -578,22 +580,10 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 		// entry point Less file we already know about.
 		$files = array_values( array_unique( $files ) );
 
-		// If a module is nothing but a list of dependencies, we need to avoid
-		// giving max() an empty array
-		if ( count( $files ) === 0 ) {
-			$this->modifiedTime[$context->getHash()] = 1;
-			return $this->modifiedTime[$context->getHash()];
-		}
-
-		$filesMtime = max( array_map( array( __CLASS__, 'safeFilemtime' ), $files ) );
-
-		$this->modifiedTime[$context->getHash()] = max(
-			$filesMtime,
-			$this->getMsgBlobMtime( $context->getLanguage() ),
-			$this->getDefinitionMtime( $context )
-		);
-
-		return $this->modifiedTime[$context->getHash()];
+		// Don't include keys or file paths here, only the hashes. Including that would needlessly
+		// cause global cache invalidation when files move or if e.g. the MediaWiki path changes.
+		// Any significant ordering is already detected by the definition summary.
+		return array_map( array( __CLASS__, 'safeFileHash' ), $files );
 	}
 
 	/**
@@ -604,7 +594,17 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	 */
 	public function getDefinitionSummary( ResourceLoaderContext $context ) {
 		$summary = parent::getDefinitionSummary( $context );
+
+		$options = array();
 		foreach ( array(
+			// The following properties are omitted because they don't affect the module reponse:
+			// - localBasePath (Per T104950; Changes when absolute directory name changes. If
+			//    this affects 'scripts' and other file paths, getFileHashes accounts for that.)
+			// - remoteBasePath (Per T104950)
+			// - dependencies (provided via startup module)
+			// - targets
+			// - group (provided via startup module)
+			// - position (only used by OutputPage)
 			'scripts',
 			'debugScripts',
 			'loaderScripts',
@@ -612,25 +612,23 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 			'languageScripts',
 			'skinScripts',
 			'skinStyles',
-			'dependencies',
 			'messages',
-			'targets',
 			'templates',
-			'group',
-			'position',
 			'skipFunction',
-			'localBasePath',
-			'remoteBasePath',
 			'debugRaw',
 			'raw',
 		) as $member ) {
-			$summary[$member] = $this->{$member};
+			$options[$member] = $this->{$member};
 		};
+
+		$summary[] = array(
+			'options' => $options,
+			'fileHashes' => $this->getFileHashes( $context ),
+			'msgBlobMtime' => $this->getMsgBlobMtime( $context->getLanguage() ),
+		);
 		return $summary;
 	}
 
-	/* Protected Methods */
-
 	/**
 	 * @param string|ResourceLoaderFilePath $path
 	 * @return string
@@ -925,10 +923,14 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 		$localDir = dirname( $localPath );
 		$remoteDir = dirname( $remotePath );
 		// Get and register local file references
-		$this->localFileRefs = array_merge(
-			$this->localFileRefs,
-			CSSMin::getLocalFileReferences( $style, $localDir )
-		);
+		$localFileRefs = CSSMin::getAllLocalFileReferences( $style, $localDir );
+		foreach ( $localFileRefs as $file ) {
+			if ( file_exists( $file ) ) {
+				$this->localFileRefs[] = $file;
+			} else {
+				$this->missingLocalFileRefs[] = $file;
+			}
+		}
 		return CSSMin::remap(
 			$style, $localDir, $remoteDir, true
 		);
@@ -958,17 +960,17 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	 * Keeps track of all used files and adds them to localFileRefs.
 	 *
 	 * @since 1.22
-	 * @throws Exception If lessc encounters a parse error
+	 * @throws Exception If less.php encounters a parse error
 	 * @param string $fileName File path of LESS source
-	 * @param lessc $compiler Compiler to use, if not default
+	 * @param Less_Parser $parser Compiler to use, if not default
 	 * @return string CSS source
 	 */
 	protected function compileLessFile( $fileName, $compiler = null ) {
 		if ( !$compiler ) {
 			$compiler = $this->getLessCompiler();
 		}
-		$result = $compiler->compileFile( $fileName );
-		$this->localFileRefs += array_keys( $compiler->allParsedFiles() );
+		$result = $compiler->parseFile( $fileName )->getCss();
+		$this->localFileRefs += array_keys( $compiler->AllParsedFiles() );
 		return $result;
 	}
 
@@ -980,7 +982,7 @@ class ResourceLoaderFileModule extends ResourceLoaderModule {
 	 * @param ResourceLoaderContext $context
 	 * @throws MWException
 	 * @since 1.24
-	 * @return lessc
+	 * @return Less_Parser
 	 */
 	protected function getLessCompiler( ResourceLoaderContext $context = null ) {
 		return ResourceLoader::getLessCompiler( $this->getConfig() );
diff --git a/includes/resourceloader/ResourceLoaderForeignApiModule.php b/includes/resourceloader/ResourceLoaderForeignApiModule.php
new file mode 100644
index 00000000..7ed08317
--- /dev/null
+++ b/includes/resourceloader/ResourceLoaderForeignApiModule.php
@@ -0,0 +1,33 @@
+<?php
+/**
+ * ResourceLoader module for mediawiki.ForeignApi that has dynamically
+ * generated dependencies, via a hook usable by extensions.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * ResourceLoader module for mediawiki.ForeignApi and its generated data
+ */
+class ResourceLoaderForeignApiModule extends ResourceLoaderFileModule {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
+		$dependencies = $this->dependencies;
+		Hooks::run( 'ResourceLoaderForeignApiModules', array( &$dependencies, $context ) );
+		return $dependencies;
+	}
+}
diff --git a/includes/resourceloader/ResourceLoaderImage.php b/includes/resourceloader/ResourceLoaderImage.php
index 12d1e827..2338c902 100644
--- a/includes/resourceloader/ResourceLoaderImage.php
+++ b/includes/resourceloader/ResourceLoaderImage.php
@@ -54,15 +54,16 @@ class ResourceLoaderImage {
 		$this->variants = $variants;
 
 		// Expand shorthands:
-		// array( "en,de,fr" => "foo.svg" ) → array( "en" => "foo.svg", "de" => "foo.svg", "fr" => "foo.svg" )
+		// array( "en,de,fr" => "foo.svg" )
+		// → array( "en" => "foo.svg", "de" => "foo.svg", "fr" => "foo.svg" )
 		if ( is_array( $this->descriptor ) && isset( $this->descriptor['lang'] ) ) {
 			foreach ( array_keys( $this->descriptor['lang'] ) as $langList ) {
 				if ( strpos( $langList, ',' ) !== false ) {
 					$this->descriptor['lang'] += array_fill_keys(
 						explode( ',', $langList ),
-						$this->descriptor['lang'][ $langList ]
+						$this->descriptor['lang'][$langList]
 					);
-					unset( $this->descriptor['lang'][ $langList ] );
+					unset( $this->descriptor['lang'][$langList] );
 				}
 			}
 		}
@@ -75,11 +76,15 @@ class ResourceLoaderImage {
 		} );
 		$extensions = array_unique( $extensions );
 		if ( count( $extensions ) !== 1 ) {
-			throw new InvalidArgumentException( "File type for different image files of '$name' not the same" );
+			throw new InvalidArgumentException(
+				"File type for different image files of '$name' not the same"
+			);
 		}
 		$ext = $extensions[0];
 		if ( !isset( self::$fileTypes[$ext] ) ) {
-			throw new InvalidArgumentException( "Invalid file type for image files of '$name' (valid: svg, png, gif, jpg)" );
+			throw new InvalidArgumentException(
+				"Invalid file type for image files of '$name' (valid: svg, png, gif, jpg)"
+			);
 		}
 		$this->extension = $ext;
 	}
@@ -117,14 +122,14 @@ class ResourceLoaderImage {
 	 * @param ResourceLoaderContext $context Any context
 	 * @return string
 	 */
-	protected function getPath( ResourceLoaderContext $context ) {
+	public function getPath( ResourceLoaderContext $context ) {
 		$desc = $this->descriptor;
 		if ( is_string( $desc ) ) {
 			return $this->basePath . '/' . $desc;
-		} elseif ( isset( $desc['lang'][ $context->getLanguage() ] ) ) {
-			return $this->basePath . '/' . $desc['lang'][ $context->getLanguage() ];
-		} elseif ( isset( $desc[ $context->getDirection() ] ) ) {
-			return $this->basePath . '/' . $desc[ $context->getDirection() ];
+		} elseif ( isset( $desc['lang'][$context->getLanguage()] ) ) {
+			return $this->basePath . '/' . $desc['lang'][$context->getLanguage()];
+		} elseif ( isset( $desc[$context->getDirection()] ) ) {
+			return $this->basePath . '/' . $desc[$context->getDirection()];
 		} else {
 			return $this->basePath . '/' . $desc['default'];
 		}
diff --git a/includes/resourceloader/ResourceLoaderImageModule.php b/includes/resourceloader/ResourceLoaderImageModule.php
index bf6a7dd2..8de87f2e 100644
--- a/includes/resourceloader/ResourceLoaderImageModule.php
+++ b/includes/resourceloader/ResourceLoaderImageModule.php
@@ -28,6 +28,8 @@
  */
 class ResourceLoaderImageModule extends ResourceLoaderModule {
 
+	protected $definition = null;
+
 	/**
 	 * Local base path, see __construct()
 	 * @var string
@@ -43,6 +45,9 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	protected $selectorWithVariant = '.{prefix}-{name}-{variant}';
 	protected $targets = array( 'desktop', 'mobile' );
 
+	/** @var string Position on the page to load this module at */
+	protected $position = 'bottom';
+
 	/**
 	 * Constructs a new module from an options array.
 	 *
@@ -57,6 +62,8 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	 *     array(
 	 *         // Base path to prepend to all local paths in $options. Defaults to $IP
 	 *         'localBasePath' => [base path],
+	 *         // Path to JSON file that contains any of the settings below
+	 *         'data' => [file path string]
 	 *         // CSS class prefix to use in all style rules
 	 *         'prefix' => [CSS class prefix],
 	 *         // Alternatively: Format of CSS selector to use in all style rules
@@ -66,21 +73,29 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	 *         'selectorWithVariant' => [CSS selector template, variables: {prefix} {name} {variant}],
 	 *         // List of variants that may be used for the image files
 	 *         'variants' => array(
+	 *             [theme name] => array(
 	 *                 [variant name] => array(
 	 *                     'color' => [color string, e.g. '#ffff00'],
 	 *                     'global' => [boolean, if true, this variant is available
 	 *                                  for all images of this type],
 	 *                 ),
+	 *                 ...
+	 *             ),
 	 *             ...
 	 *         ),
 	 *         // List of image files and their options
 	 *         'images' => array(
-	 *                 [file path string],
-	 *                 [file path string] => array(
-	 *                     'name' => [image name string, defaults to file name],
+	 *             [theme name] => array(
+	 *                 [icon name] => array(
+	 *                     'file' => [file path string or array whose values are file path strings
+	 *                                    and whose keys are 'default', 'ltr', 'rtl', a single
+	 *                                    language code like 'en', or a list of language codes like
+	 *                                    'en,de,ar'],
 	 *                     'variants' => [array of variant name strings, variants
 	 *                                    available for this image],
 	 *                 ),
+	 *                 ...
+	 *             ),
 	 *             ...
 	 *         ),
 	 *     )
@@ -90,6 +105,26 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	public function __construct( $options = array(), $localBasePath = null ) {
 		$this->localBasePath = self::extractLocalBasePath( $options, $localBasePath );
 
+		$this->definition = $options;
+	}
+
+	/**
+	 * Parse definition and external JSON data, if referenced.
+	 */
+	protected function loadFromDefinition() {
+		if ( $this->definition === null ) {
+			return;
+		}
+
+		$options = $this->definition;
+		$this->definition = null;
+
+		if ( isset( $options['data'] ) ) {
+			$dataPath = $this->localBasePath . '/' . $options['data'];
+			$data = json_decode( file_get_contents( $dataPath ), true );
+			$options = array_merge( $data, $options );
+		}
+
 		// Accepted combinations:
 		// * prefix
 		// * selector
@@ -99,20 +134,30 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 
 		$prefix = isset( $options['prefix'] ) && $options['prefix'];
 		$selector = isset( $options['selector'] ) && $options['selector'];
-		$selectorWithoutVariant = isset( $options['selectorWithoutVariant'] ) && $options['selectorWithoutVariant'];
-		$selectorWithVariant = isset( $options['selectorWithVariant'] ) && $options['selectorWithVariant'];
+		$selectorWithoutVariant = isset( $options['selectorWithoutVariant'] )
+			&& $options['selectorWithoutVariant'];
+		$selectorWithVariant = isset( $options['selectorWithVariant'] )
+			&& $options['selectorWithVariant'];
 
 		if ( $selectorWithoutVariant && !$selectorWithVariant ) {
-			throw new InvalidArgumentException( "Given 'selectorWithoutVariant' but no 'selectorWithVariant'." );
+			throw new InvalidArgumentException(
+				"Given 'selectorWithoutVariant' but no 'selectorWithVariant'."
+			);
 		}
 		if ( $selectorWithVariant && !$selectorWithoutVariant ) {
-			throw new InvalidArgumentException( "Given 'selectorWithVariant' but no 'selectorWithoutVariant'." );
+			throw new InvalidArgumentException(
+				"Given 'selectorWithVariant' but no 'selectorWithoutVariant'."
+			);
 		}
 		if ( $selector && $selectorWithVariant ) {
-			throw new InvalidArgumentException( "Incompatible 'selector' and 'selectorWithVariant'+'selectorWithoutVariant' given." );
+			throw new InvalidArgumentException(
+				"Incompatible 'selector' and 'selectorWithVariant'+'selectorWithoutVariant' given."
+			);
 		}
 		if ( !$prefix && !$selector && !$selectorWithVariant ) {
-			throw new InvalidArgumentException( "None of 'prefix', 'selector' or 'selectorWithVariant'+'selectorWithoutVariant' given." );
+			throw new InvalidArgumentException(
+				"None of 'prefix', 'selector' or 'selectorWithVariant'+'selectorWithoutVariant' given."
+			);
 		}
 
 		foreach ( $options as $member => $option ) {
@@ -124,9 +169,22 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 							"Invalid list error. '$option' given, array expected."
 						);
 					}
+					if ( !isset( $option['default'] ) ) {
+						// Backwards compatibility
+						$option = array( 'default' => $option );
+					}
+					foreach ( $option as $skin => $data ) {
+						if ( !is_array( $option ) ) {
+							throw new InvalidArgumentException(
+								"Invalid list error. '$option' given, array expected."
+							);
+						}
+					}
 					$this->{$member} = $option;
 					break;
 
+				case 'position':
+					$this->isPositionDefined = true;
 				case 'prefix':
 				case 'selectorWithoutVariant':
 				case 'selectorWithVariant':
@@ -144,6 +202,7 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	 * @return string
 	 */
 	public function getPrefix() {
+		$this->loadFromDefinition();
 		return $this->prefix;
 	}
 
@@ -152,6 +211,7 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	 * @return string
 	 */
 	public function getSelectors() {
+		$this->loadFromDefinition();
 		return array(
 			'selectorWithoutVariant' => $this->selectorWithoutVariant,
 			'selectorWithVariant' => $this->selectorWithVariant,
@@ -161,31 +221,43 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	/**
 	 * Get a ResourceLoaderImage object for given image.
 	 * @param string $name Image name
+	 * @param ResourceLoaderContext $context
 	 * @return ResourceLoaderImage|null
 	 */
-	public function getImage( $name ) {
-		$images = $this->getImages();
+	public function getImage( $name, ResourceLoaderContext $context ) {
+		$this->loadFromDefinition();
+		$images = $this->getImages( $context );
 		return isset( $images[$name] ) ? $images[$name] : null;
 	}
 
 	/**
 	 * Get ResourceLoaderImage objects for all images.
+	 * @param ResourceLoaderContext $context
 	 * @return ResourceLoaderImage[] Array keyed by image name
 	 */
-	public function getImages() {
+	public function getImages( ResourceLoaderContext $context ) {
+		$skin = $context->getSkin();
 		if ( !isset( $this->imageObjects ) ) {
+			$this->loadFromDefinition();
 			$this->imageObjects = array();
-
-			foreach ( $this->images as $name => $options ) {
+		}
+		if ( !isset( $this->imageObjects[$skin] ) ) {
+			$this->imageObjects[$skin] = array();
+			if ( !isset( $this->images[$skin] ) ) {
+				$this->images[$skin] = isset( $this->images['default'] ) ?
+					$this->images['default'] :
+					array();
+			}
+			foreach ( $this->images[$skin] as $name => $options ) {
 				$fileDescriptor = is_string( $options ) ? $options : $options['file'];
 
 				$allowedVariants = array_merge(
 					is_array( $options ) && isset( $options['variants'] ) ? $options['variants'] : array(),
-					$this->getGlobalVariants()
+					$this->getGlobalVariants( $context )
 				);
-				if ( isset( $this->variants ) ) {
+				if ( isset( $this->variants[$skin] ) ) {
 					$variantConfig = array_intersect_key(
-						$this->variants,
+						$this->variants[$skin],
 						array_fill_keys( $allowedVariants, true )
 					);
 				} else {
@@ -199,32 +271,40 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 					$this->localBasePath,
 					$variantConfig
 				);
-				$this->imageObjects[ $image->getName() ] = $image;
+				$this->imageObjects[$skin][$image->getName()] = $image;
 			}
 		}
 
-		return $this->imageObjects;
+		return $this->imageObjects[$skin];
 	}
 
 	/**
 	 * Get list of variants in this module that are 'global', i.e., available
 	 * for every image regardless of image options.
+	 * @param ResourceLoaderContext $context
 	 * @return string[]
 	 */
-	public function getGlobalVariants() {
+	public function getGlobalVariants( ResourceLoaderContext $context ) {
+		$skin = $context->getSkin();
 		if ( !isset( $this->globalVariants ) ) {
+			$this->loadFromDefinition();
 			$this->globalVariants = array();
-
-			if ( isset( $this->variants ) ) {
-				foreach ( $this->variants as $name => $config ) {
-					if ( isset( $config['global'] ) && $config['global'] ) {
-						$this->globalVariants[] = $name;
-					}
+		}
+		if ( !isset( $this->globalVariants[$skin] ) ) {
+			$this->globalVariants[$skin] = array();
+			if ( !isset( $this->variants[$skin] ) ) {
+				$this->variants[$skin] = isset( $this->variants['default'] ) ?
+					$this->variants['default'] :
+					array();
+			}
+			foreach ( $this->variants[$skin] as $name => $config ) {
+				if ( isset( $config['global'] ) && $config['global'] ) {
+					$this->globalVariants[$skin][] = $name;
 				}
 			}
 		}
 
-		return $this->globalVariants;
+		return $this->globalVariants[$skin];
 	}
 
 	/**
@@ -232,12 +312,14 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	 * @return array
 	 */
 	public function getStyles( ResourceLoaderContext $context ) {
+		$this->loadFromDefinition();
+
 		// Build CSS rules
 		$rules = array();
 		$script = $context->getResourceLoader()->getLoadScript( $this->getSource() );
 		$selectors = $this->getSelectors();
 
-		foreach ( $this->getImages() as $name => $image ) {
+		foreach ( $this->getImages( $context ) as $name => $image ) {
 			$declarations = $this->getCssDeclarations(
 				$image->getDataUri( $context, null, 'original' ),
 				$image->getUrl( $context, $script, null, 'rasterized' )
@@ -304,6 +386,48 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 	}
 
 	/**
+	 * Get the definition summary for this module.
+	 *
+	 * @param ResourceLoaderContext $context
+	 * @return array
+	 */
+	public function getDefinitionSummary( ResourceLoaderContext $context ) {
+		$this->loadFromDefinition();
+		$summary = parent::getDefinitionSummary( $context );
+		foreach ( array(
+			'localBasePath',
+			'images',
+			'variants',
+			'prefix',
+			'selectorWithoutVariant',
+			'selectorWithVariant',
+		) as $member ) {
+			$summary[$member] = $this->{$member};
+		};
+		return $summary;
+	}
+
+	/**
+	 * Get the last modified timestamp of this module.
+	 *
+	 * @param ResourceLoaderContext $context Context in which to calculate
+	 *     the modified time
+	 * @return int UNIX timestamp
+	 */
+	public function getModifiedTime( ResourceLoaderContext $context ) {
+		$this->loadFromDefinition();
+		$files = array();
+		foreach ( $this->getImages( $context ) as $name => $image ) {
+			$files[] = $image->getPath( $context );
+		}
+
+		$files = array_values( array_unique( $files ) );
+		$filesMtime = max( array_map( array( __CLASS__, 'safeFilemtime' ), $files ) );
+
+		return $filesMtime;
+	}
+
+	/**
 	 * Extract a local base path from module definition information.
 	 *
 	 * @param array $options Module definition
@@ -324,4 +448,17 @@ class ResourceLoaderImageModule extends ResourceLoaderModule {
 
 		return $localBasePath;
 	}
+
+	/**
+	 * @return string
+	 */
+	public function getPosition() {
+		$this->loadFromDefinition();
+		return $this->position;
+	}
+
+	public function isPositionDefault() {
+		$this->loadFromDefinition();
+		return parent::isPositionDefault();
+	}
 }
diff --git a/includes/resourceloader/ResourceLoaderJqueryMsgModule.php b/includes/resourceloader/ResourceLoaderJqueryMsgModule.php
new file mode 100644
index 00000000..f9dfbdc2
--- /dev/null
+++ b/includes/resourceloader/ResourceLoaderJqueryMsgModule.php
@@ -0,0 +1,66 @@
+<?php
+/**
+ * ResourceLoader module for mediawiki.jqueryMsg that provides generated data.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Brad Jorsch
+ */
+
+/**
+ * ResourceLoader module for mediawiki.jqueryMsg and its generated data
+ */
+class ResourceLoaderJqueryMsgModule extends ResourceLoaderFileModule {
+
+	/**
+	 * @param ResourceLoaderContext $context
+	 * @return string JavaScript code
+	 */
+	public function getScript( ResourceLoaderContext $context ) {
+		$fileScript = parent::getScript( $context );
+
+		$tagData = Sanitizer::getRecognizedTagData();
+		$parserDefaults = array();
+		$parserDefaults['allowedHtmlElements'] = array_merge(
+			array_keys( $tagData['htmlpairs'] ),
+			array_diff(
+				array_keys( $tagData['htmlsingle'] ),
+				array_keys( $tagData['htmlsingleonly'] )
+			)
+		);
+
+		$dataScript = Xml::encodeJsCall( 'mw.jqueryMsg.setParserDefaults', array( $parserDefaults ) );
+
+		return $fileScript . $dataScript;
+	}
+
+	/**
+	* @param ResourceLoaderContext $context
+	* @return array
+	*/
+	public function getScriptURLsForDebug( ResourceLoaderContext $context ) {
+		// Bypass file module urls
+		return ResourceLoaderModule::getScriptURLsForDebug( $context );
+	}
+
+	/**
+	 * @return bool
+	 */
+	public function enableModuleContentVersion() {
+		return true;
+	}
+}
diff --git a/includes/resourceloader/ResourceLoaderLanguageDataModule.php b/includes/resourceloader/ResourceLoaderLanguageDataModule.php
index 12394536..27c74d74 100644
--- a/includes/resourceloader/ResourceLoaderLanguageDataModule.php
+++ b/includes/resourceloader/ResourceLoaderLanguageDataModule.php
@@ -63,25 +63,17 @@ class ResourceLoaderLanguageDataModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return max( 1, $this->getHashMtime( $context ) );
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
 	 * @param ResourceLoaderContext $context
-	 * @return string Hash
-	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return md5( serialize( $this->getData( $context ) ) );
-	}
-
-	/**
 	 * @return array
 	 */
-	public function getDependencies() {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
 		return array( 'mediawiki.language.init' );
 	}
 }
diff --git a/includes/resourceloader/ResourceLoaderLanguageNamesModule.php b/includes/resourceloader/ResourceLoaderLanguageNamesModule.php
index 55b1f4b1..081c728c 100644
--- a/includes/resourceloader/ResourceLoaderLanguageNamesModule.php
+++ b/includes/resourceloader/ResourceLoaderLanguageNamesModule.php
@@ -32,7 +32,6 @@ class ResourceLoaderLanguageNamesModule extends ResourceLoaderModule {
 
 	protected $targets = array( 'desktop', 'mobile' );
 
-
 	/**
 	 * @param ResourceLoaderContext $context
 	 * @return array
@@ -60,24 +59,19 @@ class ResourceLoaderLanguageNamesModule extends ResourceLoaderModule {
 		);
 	}
 
-	public function getDependencies() {
-		return array( 'mediawiki.language.init' );
-	}
-
 	/**
 	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
+	 * @return array
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return max( 1, $this->getHashMtime( $context ) );
+	public function getDependencies( ResourceLoaderContext $context = null ) {
+		return array( 'mediawiki.language.init' );
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return string Hash
+	 * @return bool
 	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return md5( serialize( $this->getData( $context ) ) );
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 }
diff --git a/includes/resourceloader/ResourceLoaderModule.php b/includes/resourceloader/ResourceLoaderModule.php
index ed16521b..1d3ffb55 100644
--- a/includes/resourceloader/ResourceLoaderModule.php
+++ b/includes/resourceloader/ResourceLoaderModule.php
@@ -29,7 +29,6 @@ abstract class ResourceLoaderModule {
 	# Type of resource
 	const TYPE_SCRIPTS = 'scripts';
 	const TYPE_STYLES = 'styles';
-	const TYPE_MESSAGES = 'messages';
 	const TYPE_COMBINED = 'combined';
 
 	# sitewide core module like a skin file or jQuery component
@@ -63,6 +62,14 @@ abstract class ResourceLoaderModule {
 	protected $fileDeps = array();
 	// In-object cache for message blob mtime
 	protected $msgBlobMtime = array();
+	// In-object cache for version hash
+	protected $versionHash = array();
+	// In-object cache for module content
+	protected $contents = array();
+
+	// Whether the position returned by getPosition() is defined in the module configuration
+	// and not a default value
+	protected $isPositionDefined = false;
 
 	/**
 	 * @var Config
@@ -285,6 +292,19 @@ abstract class ResourceLoaderModule {
 	}
 
 	/**
+	 * Whether the position returned by getPosition() is a default value or comes from the module
+	 * definition. This method is meant to be short-lived, and is only useful until classes added
+	 * via addModuleStyles with a default value define an explicit position. See getModuleStyles()
+	 * in OutputPage for the related migration warning.
+	 *
+	 * @return bool
+	 * @since  1.26
+	 */
+	public function isPositionDefault() {
+		return !$this->isPositionDefined;
+	}
+
+	/**
 	 * Whether this module's JS expects to work without the client-side ResourceLoader module.
 	 * Returning true from this function will prevent mw.loader.state() call from being
 	 * appended to the bottom of the script.
@@ -313,9 +333,14 @@ abstract class ResourceLoaderModule {
 	 *
 	 * To add dependencies dynamically on the client side, use a custom
 	 * loader script, see getLoaderScript()
+	 *
+	 * Note: It is expected that $context will be made non-optional in the near
+	 * future.
+	 *
+	 * @param ResourceLoaderContext $context
 	 * @return array List of module names as strings
 	 */
-	public function getDependencies() {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
 		// Stub, override expected
 		return array();
 	}
@@ -361,16 +386,21 @@ abstract class ResourceLoaderModule {
 		}
 
 		$dbr = wfGetDB( DB_SLAVE );
-		$deps = $dbr->selectField( 'module_deps', 'md_deps', array(
+		$deps = $dbr->selectField( 'module_deps',
+			'md_deps',
+			array(
 				'md_module' => $this->getName(),
 				'md_skin' => $skin,
-			), __METHOD__
+			),
+			__METHOD__
 		);
+
 		if ( !is_null( $deps ) ) {
 			$this->fileDeps[$skin] = (array)FormatJson::decode( $deps, true );
 		} else {
 			$this->fileDeps[$skin] = array();
 		}
+
 		return $this->fileDeps[$skin];
 	}
 
@@ -385,8 +415,7 @@ abstract class ResourceLoaderModule {
 	}
 
 	/**
-	 * Get the last modification timestamp of the message blob for this
-	 * module in a given language.
+	 * Get the last modification timestamp of the messages in this module for a given language.
 	 * @param string $lang Language code
 	 * @return int UNIX timestamp
 	 */
@@ -397,10 +426,13 @@ abstract class ResourceLoaderModule {
 			}
 
 			$dbr = wfGetDB( DB_SLAVE );
-			$msgBlobMtime = $dbr->selectField( 'msg_resource', 'mr_timestamp', array(
+			$msgBlobMtime = $dbr->selectField( 'msg_resource',
+				'mr_timestamp',
+				array(
 					'mr_resource' => $this->getName(),
 					'mr_lang' => $lang
-				), __METHOD__
+				),
+				__METHOD__
 			);
 			// If no blob was found, but the module does have messages, that means we need
 			// to regenerate it. Return NOW
@@ -422,144 +454,318 @@ abstract class ResourceLoaderModule {
 		$this->msgBlobMtime[$lang] = $mtime;
 	}
 
-	/* Abstract Methods */
-
 	/**
-	 * Get this module's last modification timestamp for a given
-	 * combination of language, skin and debug mode flag. This is typically
-	 * the highest of each of the relevant components' modification
-	 * timestamps. Whenever anything happens that changes the module's
-	 * contents for these parameters, the mtime should increase.
-	 *
-	 * NOTE: The mtime of the module's messages is NOT automatically included.
-	 * If you want this to happen, you'll need to call getMsgBlobMtime()
-	 * yourself and take its result into consideration.
-	 *
-	 * NOTE: The mtime of the module's hash is NOT automatically included.
-	 * If your module provides a getModifiedHash() method, you'll need to call getHashMtime()
-	 * yourself and take its result into consideration.
+	 * Get an array of this module's resources. Ready for serving to the web.
 	 *
-	 * @param ResourceLoaderContext $context Context object
-	 * @return int UNIX timestamp
-	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return 1;
+	 * @since 1.26
+	 * @param ResourceLoaderContext $context
+	 * @return array
+	 */
+	public function getModuleContent( ResourceLoaderContext $context ) {
+		$contextHash = $context->getHash();
+		// Cache this expensive operation. This calls builds the scripts, styles, and messages
+		// content which typically involves filesystem and/or database access.
+		if ( !array_key_exists( $contextHash, $this->contents ) ) {
+			$this->contents[$contextHash] = $this->buildContent( $context );
+		}
+		return $this->contents[$contextHash];
 	}
 
 	/**
-	 * Helper method for calculating when the module's hash (if it has one) changed.
+	 * Bundle all resources attached to this module into an array.
 	 *
+	 * @since 1.26
 	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
-	 */
-	public function getHashMtime( ResourceLoaderContext $context ) {
-		$hash = $this->getModifiedHash( $context );
-		if ( !is_string( $hash ) ) {
-			return 1;
+	 * @return array
+	 */
+	final protected function buildContent( ResourceLoaderContext $context ) {
+		$rl = $context->getResourceLoader();
+		$stats = RequestContext::getMain()->getStats();
+		$statStart = microtime( true );
+
+		// Only include properties that are relevant to this context (e.g. only=scripts)
+		// and that are non-empty (e.g. don't include "templates" for modules without
+		// templates). This helps prevent invalidating cache for all modules when new
+		// optional properties are introduced.
+		$content = array();
+
+		// Scripts
+		if ( $context->shouldIncludeScripts() ) {
+			// If we are in debug mode, we'll want to return an array of URLs if possible
+			// However, we can't do this if the module doesn't support it
+			// We also can't do this if there is an only= parameter, because we have to give
+			// the module a way to return a load.php URL without causing an infinite loop
+			if ( $context->getDebug() && !$context->getOnly() && $this->supportsURLLoading() ) {
+				$scripts = $this->getScriptURLsForDebug( $context );
+			} else {
+				$scripts = $this->getScript( $context );
+				// rtrim() because there are usually a few line breaks
+				// after the last ';'. A new line at EOF, a new line
+				// added by ResourceLoaderFileModule::readScriptFiles, etc.
+				if ( is_string( $scripts )
+					&& strlen( $scripts )
+					&& substr( rtrim( $scripts ), -1 ) !== ';'
+				) {
+					// Append semicolon to prevent weird bugs caused by files not
+					// terminating their statements right (bug 27054)
+					$scripts .= ";\n";
+				}
+			}
+			$content['scripts'] = $scripts;
+		}
+
+		// Styles
+		if ( $context->shouldIncludeStyles() ) {
+			$styles = array();
+			// Don't create empty stylesheets like array( '' => '' ) for modules
+			// that don't *have* any stylesheets (bug 38024).
+			$stylePairs = $this->getStyles( $context );
+			if ( count( $stylePairs ) ) {
+				// If we are in debug mode without &only= set, we'll want to return an array of URLs
+				// See comment near shouldIncludeScripts() for more details
+				if ( $context->getDebug() && !$context->getOnly() && $this->supportsURLLoading() ) {
+					$styles = array(
+						'url' => $this->getStyleURLsForDebug( $context )
+					);
+				} else {
+					// Minify CSS before embedding in mw.loader.implement call
+					// (unless in debug mode)
+					if ( !$context->getDebug() ) {
+						foreach ( $stylePairs as $media => $style ) {
+							// Can be either a string or an array of strings.
+							if ( is_array( $style ) ) {
+								$stylePairs[$media] = array();
+								foreach ( $style as $cssText ) {
+									if ( is_string( $cssText ) ) {
+										$stylePairs[$media][] =
+											$rl->filter( 'minify-css', $cssText );
+									}
+								}
+							} elseif ( is_string( $style ) ) {
+								$stylePairs[$media] = $rl->filter( 'minify-css', $style );
+							}
+						}
+					}
+					// Wrap styles into @media groups as needed and flatten into a numerical array
+					$styles = array(
+						'css' => $rl->makeCombinedStyles( $stylePairs )
+					);
+				}
+			}
+			$content['styles'] = $styles;
+		}
+
+		// Messages
+		$blobs = $rl->getMessageBlobStore()->get(
+			$rl,
+			array( $this->getName() => $this ),
+			$context->getLanguage()
+		);
+		if ( isset( $blobs[$this->getName()] ) ) {
+			$content['messagesBlob'] = $blobs[$this->getName()];
 		}
 
-		// Embed the hash itself in the cache key. This allows for a few nifty things:
-		// - During deployment, servers with old and new versions of the code communicating
-		//   with the same memcached will not override the same key repeatedly increasing
-		//   the timestamp.
-		// - In case of the definition changing and then changing back in a short period of time
-		//   (e.g. in case of a revert or a corrupt server) the old timestamp and client-side cache
-		//   url will be re-used.
-		// - If different context-combinations (e.g. same skin, same language or some combination
-		//   thereof) result in the same definition, they will use the same hash and timestamp.
-		$cache = wfGetCache( CACHE_ANYTHING );
-		$key = wfMemcKey( 'resourceloader', 'hashmtime', $this->getName(), $hash );
-
-		$data = $cache->get( $key );
-		if ( is_int( $data ) && $data > 0 ) {
-			// We've seen this hash before, re-use the timestamp of when we first saw it.
-			return $data;
+		$templates = $this->getTemplates();
+		if ( $templates ) {
+			$content['templates'] = $templates;
 		}
 
-		$timestamp = time();
-		$cache->set( $key, $timestamp );
-		return $timestamp;
+		$statTiming = microtime( true ) - $statStart;
+		$statName = strtr( $this->getName(), '.', '_' );
+		$stats->timing( "resourceloader_build.all", 1000 * $statTiming );
+		$stats->timing( "resourceloader_build.$statName", 1000 * $statTiming );
+
+		return $content;
 	}
 
 	/**
-	 * Get the hash for whatever this module may contain.
+	 * Get a string identifying the current version of this module in a given context.
+	 *
+	 * Whenever anything happens that changes the module's response (e.g. scripts, styles, and
+	 * messages) this value must change. This value is used to store module responses in cache.
+	 * (Both client-side and server-side.)
 	 *
-	 * This is the method subclasses should implement if they want to make
-	 * use of getHashMTime() inside getModifiedTime().
+	 * It is not recommended to override this directly. Use getDefinitionSummary() instead.
+	 * If overridden, one must call the parent getVersionHash(), append data and re-hash.
 	 *
+	 * This method should be quick because it is frequently run by ResourceLoaderStartUpModule to
+	 * propagate changes to the client and effectively invalidate cache.
+	 *
+	 * For backward-compatibility, the following optional data providers are automatically included:
+	 *
+	 * - getModifiedTime()
+	 * - getModifiedHash()
+	 *
+	 * @since 1.26
 	 * @param ResourceLoaderContext $context
-	 * @return string|null Hash
-	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return null;
+	 * @return string Hash (should use ResourceLoader::makeHash)
+	 */
+	public function getVersionHash( ResourceLoaderContext $context ) {
+		// The startup module produces a manifest with versions representing the entire module.
+		// Typically, the request for the startup module itself has only=scripts. That must apply
+		// only to the startup module content, and not to the module version computed here.
+		$context = new DerivativeResourceLoaderContext( $context );
+		$context->setModules( array() );
+		// Version hash must cover all resources, regardless of startup request itself.
+		$context->setOnly( null );
+		// Compute version hash based on content, not debug urls.
+		$context->setDebug( false );
+
+		// Cache this somewhat expensive operation. Especially because some classes
+		// (e.g. startup module) iterate more than once over all modules to get versions.
+		$contextHash = $context->getHash();
+		if ( !array_key_exists( $contextHash, $this->versionHash ) ) {
+
+			if ( $this->enableModuleContentVersion() ) {
+				// Detect changes directly
+				$str = json_encode( $this->getModuleContent( $context ) );
+			} else {
+				// Infer changes based on definition and other metrics
+				$summary = $this->getDefinitionSummary( $context );
+				if ( !isset( $summary['_cacheEpoch'] ) ) {
+					throw new LogicException( 'getDefinitionSummary must call parent method' );
+				}
+				$str = json_encode( $summary );
+
+				$mtime = $this->getModifiedTime( $context );
+				if ( $mtime !== null ) {
+					// Support: MediaWiki 1.25 and earlier
+					$str .= strval( $mtime );
+				}
+
+				$mhash = $this->getModifiedHash( $context );
+				if ( $mhash !== null ) {
+					// Support: MediaWiki 1.25 and earlier
+					$str .= strval( $mhash );
+				}
+			}
+
+			$this->versionHash[$contextHash] = ResourceLoader::makeHash( $str );
+		}
+		return $this->versionHash[$contextHash];
 	}
 
 	/**
-	 * Helper method for calculating when this module's definition summary was last changed.
+	 * Whether to generate version hash based on module content.
 	 *
-	 * @since 1.23
+	 * If a module requires database or file system access to build the module
+	 * content, consider disabling this in favour of manually tracking relevant
+	 * aspects in getDefinitionSummary(). See getVersionHash() for how this is used.
 	 *
-	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
+	 * @return bool
 	 */
-	public function getDefinitionMtime( ResourceLoaderContext $context ) {
-		$summary = $this->getDefinitionSummary( $context );
-		if ( $summary === null ) {
-			return 1;
-		}
-
-		$hash = md5( json_encode( $summary ) );
-		$cache = wfGetCache( CACHE_ANYTHING );
-		$key = wfMemcKey( 'resourceloader', 'moduledefinition', $this->getName(), $hash );
-
-		$data = $cache->get( $key );
-		if ( is_int( $data ) && $data > 0 ) {
-			// We've seen this hash before, re-use the timestamp of when we first saw it.
-			return $data;
-		}
-
-		wfDebugLog( 'resourceloader', __METHOD__ . ": New definition for module "
-			. "{$this->getName()} in context \"{$context->getHash()}\"" );
-
-		$timestamp = time();
-		$cache->set( $key, $timestamp );
-		return $timestamp;
+	public function enableModuleContentVersion() {
+		return false;
 	}
 
 	/**
 	 * Get the definition summary for this module.
 	 *
-	 * This is the method subclasses should implement if they want to make
-	 * use of getDefinitionMTime() inside getModifiedTime().
+	 * This is the method subclasses are recommended to use to track values in their
+	 * version hash. Call this in getVersionHash() and pass it to e.g. json_encode.
+	 *
+	 * Subclasses must call the parent getDefinitionSummary() and build on that.
+	 * It is recommended that each subclass appends its own new array. This prevents
+	 * clashes or accidental overwrites of existing keys and gives each subclass
+	 * its own scope for simple array keys.
+	 *
+	 * @code
+	 *     $summary = parent::getDefinitionSummary( $context );
+	 *     $summary[] = array(
+	 *         'foo' => 123,
+	 *         'bar' => 'quux',
+	 *     );
+	 *     return $summary;
+	 * @endcode
 	 *
 	 * Return an array containing values from all significant properties of this
-	 * module's definition. Be sure to include things that are explicitly ordered,
-	 * in their actaul order (bug 37812).
+	 * module's definition.
 	 *
-	 * Avoid including things that are insiginificant (e.g. order of message
-	 * keys is insignificant and should be sorted to avoid unnecessary cache
-	 * invalidation).
+	 * Be careful not to normalise too much. Especially preserve the order of things
+	 * that carry significance in getScript and getStyles (T39812).
 	 *
-	 * Avoid including things already considered by other methods inside your
-	 * getModifiedTime(), such as file mtime timestamps.
+	 * Avoid including things that are insiginificant (e.g. order of message keys is
+	 * insignificant and should be sorted to avoid unnecessary cache invalidation).
 	 *
-	 * Serialisation is done using json_encode, which means object state is not
-	 * taken into account when building the hash. This data structure must only
-	 * contain arrays and scalars as values (avoid object instances) which means
-	 * it requires abstraction.
+	 * This data structure must exclusively contain arrays and scalars as values (avoid
+	 * object instances) to allow simple serialisation using json_encode.
 	 *
-	 * @since 1.23
+	 * If modules have a hash or timestamp from another source, that may be incuded as-is.
 	 *
+	 * A number of utility methods are available to help you gather data. These are not
+	 * called by default and must be included by the subclass' getDefinitionSummary().
+	 *
+	 * - getMsgBlobMtime()
+	 *
+	 * @since 1.23
 	 * @param ResourceLoaderContext $context
 	 * @return array|null
 	 */
 	public function getDefinitionSummary( ResourceLoaderContext $context ) {
 		return array(
-			'class' => get_class( $this ),
+			'_class' => get_class( $this ),
+			'_cacheEpoch' => $this->getConfig()->get( 'CacheEpoch' ),
 		);
 	}
 
 	/**
+	 * Get this module's last modification timestamp for a given context.
+	 *
+	 * @deprecated since 1.26 Use getDefinitionSummary() instead
+	 * @param ResourceLoaderContext $context Context object
+	 * @return int|null UNIX timestamp
+	 */
+	public function getModifiedTime( ResourceLoaderContext $context ) {
+		return null;
+	}
+
+	/**
+	 * Helper method for providing a version hash to getVersionHash().
+	 *
+	 * @deprecated since 1.26 Use getDefinitionSummary() instead
+	 * @param ResourceLoaderContext $context
+	 * @return string|null Hash
+	 */
+	public function getModifiedHash( ResourceLoaderContext $context ) {
+		return null;
+	}
+
+	/**
+	 * Back-compat dummy for old subclass implementations of getModifiedTime().
+	 *
+	 * This method used to use ObjectCache to track when a hash was first seen. That principle
+	 * stems from a time that ResourceLoader could only identify module versions by timestamp.
+	 * That is no longer the case. Use getDefinitionSummary() directly.
+	 *
+	 * @deprecated since 1.26 Superseded by getVersionHash()
+	 * @param ResourceLoaderContext $context
+	 * @return int UNIX timestamp
+	 */
+	public function getHashMtime( ResourceLoaderContext $context ) {
+		if ( !is_string( $this->getModifiedHash( $context ) ) ) {
+			return 1;
+		}
+		// Dummy that is > 1
+		return 2;
+	}
+
+	/**
+	 * Back-compat dummy for old subclass implementations of getModifiedTime().
+	 *
+	 * @since 1.23
+	 * @deprecated since 1.26 Superseded by getVersionHash()
+	 * @param ResourceLoaderContext $context
+	 * @return int UNIX timestamp
+	 */
+	public function getDefinitionMtime( ResourceLoaderContext $context ) {
+		if ( $this->getDefinitionSummary( $context ) === null ) {
+			return 1;
+		}
+		// Dummy that is > 1
+		return 2;
+	}
+
+	/**
 	 * Check whether this module is known to be empty. If a child class
 	 * has an easy and cheap way to determine that this module is
 	 * definitely going to be empty, it should override this method to
@@ -587,8 +793,13 @@ abstract class ResourceLoaderModule {
 	protected function validateScriptFile( $fileName, $contents ) {
 		if ( $this->getConfig()->get( 'ResourceLoaderValidateJS' ) ) {
 			// Try for cache hit
-			// Use CACHE_ANYTHING since filtering is very slow compared to DB queries
-			$key = wfMemcKey( 'resourceloader', 'jsparse', self::$parseCacheVersion, md5( $contents ) );
+			// Use CACHE_ANYTHING since parsing JS is much slower than a DB query
+			$key = wfMemcKey(
+				'resourceloader',
+				'jsparse',
+				self::$parseCacheVersion,
+				md5( $contents )
+			);
 			$cache = wfGetCache( CACHE_ANYTHING );
 			$cacheEntry = $cache->get( $key );
 			if ( is_string( $cacheEntry ) ) {
@@ -602,7 +813,8 @@ abstract class ResourceLoaderModule {
 			} catch ( Exception $e ) {
 				// We'll save this to cache to avoid having to validate broken JS over and over...
 				$err = $e->getMessage();
-				$result = "throw new Error(" . Xml::encodeJsVar( "JavaScript parse error: $err" ) . ");";
+				$result = "mw.log.error(" .
+					Xml::encodeJsVar( "JavaScript parse error: $err" ) . ");";
 			}
 
 			$cache->set( $key, $result );
@@ -623,16 +835,57 @@ abstract class ResourceLoaderModule {
 	}
 
 	/**
-	 * Safe version of filemtime(), which doesn't throw a PHP warning if the file doesn't exist
-	 * but returns 1 instead.
-	 * @param string $filename File name
+	 * Safe version of filemtime(), which doesn't throw a PHP warning if the file doesn't exist.
+	 * Defaults to 1.
+	 *
+	 * @param string $filePath File path
 	 * @return int UNIX timestamp
 	 */
-	protected static function safeFilemtime( $filename ) {
-		wfSuppressWarnings();
-		$mtime = filemtime( $filename ) ?: 1;
-		wfRestoreWarnings();
-
+	protected static function safeFilemtime( $filePath ) {
+		MediaWiki\suppressWarnings();
+		$mtime = filemtime( $filePath ) ?: 1;
+		MediaWiki\restoreWarnings();
 		return $mtime;
 	}
+
+	/**
+	 * Compute a non-cryptographic string hash of a file's contents.
+	 * If the file does not exist or cannot be read, returns an empty string.
+	 *
+	 * @since 1.26 Uses MD4 instead of SHA1.
+	 * @param string $filePath File path
+	 * @return string Hash
+	 */
+	protected static function safeFileHash( $filePath ) {
+		static $cache;
+
+		if ( !$cache ) {
+			$cache = ObjectCache::newAccelerator( CACHE_NONE );
+		}
+
+		MediaWiki\suppressWarnings();
+		$mtime = filemtime( $filePath );
+		MediaWiki\restoreWarnings();
+		if ( !$mtime ) {
+			return '';
+		}
+
+		$cacheKey = wfGlobalCacheKey( 'resourceloader', __METHOD__, $filePath );
+		$cachedHash = $cache->get( $cacheKey );
+		if ( isset( $cachedHash['mtime'] ) && $cachedHash['mtime'] === $mtime ) {
+			return $cachedHash['hash'];
+		}
+
+		MediaWiki\suppressWarnings();
+		$contents = file_get_contents( $filePath );
+		MediaWiki\restoreWarnings();
+		if ( !$contents ) {
+			return '';
+		}
+
+		$hash = hash( 'md4', $contents );
+		$cache->set( $cacheKey, array( 'mtime' => $mtime, 'hash' => $hash ), 60 * 60 * 24 );
+
+		return $hash;
+	}
 }
diff --git a/includes/resourceloader/ResourceLoaderOOUIImageModule.php b/includes/resourceloader/ResourceLoaderOOUIImageModule.php
new file mode 100644
index 00000000..8493f9fd
--- /dev/null
+++ b/includes/resourceloader/ResourceLoaderOOUIImageModule.php
@@ -0,0 +1,86 @@
+<?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * Secret special sauce.
+ *
+ * @since 1.26
+ */
+class ResourceLoaderOOUIImageModule extends ResourceLoaderImageModule {
+	protected function loadFromDefinition() {
+		if ( $this->definition === null ) {
+			return;
+		}
+
+		// Core default themes
+		$themes = array( 'default' => 'mediawiki' );
+		$themes += ExtensionRegistry::getInstance()->getAttribute( 'SkinOOUIThemes' );
+
+		$name = $this->definition['name'];
+		$rootPath = $this->definition['rootPath'];
+
+		$definition = array();
+		foreach ( $themes as $skin => $theme ) {
+			// TODO Allow extensions to specify this path somehow
+			$dataPath = $this->localBasePath . '/' . $rootPath . '/' . $theme . '/' . $name . '.json';
+
+			if ( file_exists( $dataPath ) ) {
+				$data = json_decode( file_get_contents( $dataPath ), true );
+				$fixPath = function ( &$path ) use ( $rootPath, $theme ) {
+					// TODO Allow extensions to specify this path somehow
+					$path = $rootPath . '/' . $theme . '/' . $path;
+				};
+				array_walk( $data['images'], function ( &$value ) use ( $fixPath ) {
+					if ( is_string( $value['file'] ) ) {
+						$fixPath( $value['file'] );
+					} elseif ( is_array( $value['file'] ) ) {
+						array_walk_recursive( $value['file'], $fixPath );
+					}
+				} );
+			} else {
+				$data = array();
+			}
+
+			foreach ( $data as $key => $value ) {
+				switch ( $key ) {
+					case 'images':
+					case 'variants':
+						$definition[$key][$skin] = $data[$key];
+						break;
+
+					default:
+						if ( !isset( $definition[$key] ) ) {
+							$definition[$key] = $data[$key];
+						} elseif ( $definition[$key] !== $data[$key] ) {
+							throw new Exception(
+								"Mismatched OOUI theme definitions are not supported: trying to load $key of $theme theme"
+							);
+						}
+						break;
+				}
+			}
+		}
+
+		// Fields from definition silently override keys from JSON files
+		$this->definition += $definition;
+
+		parent::loadFromDefinition();
+	}
+}
diff --git a/includes/resourceloader/ResourceLoaderRawFileModule.php b/includes/resourceloader/ResourceLoaderRawFileModule.php
new file mode 100644
index 00000000..d9005fa5
--- /dev/null
+++ b/includes/resourceloader/ResourceLoaderRawFileModule.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Module containing files that are loaded without ResourceLoader.
+ *
+ * Primary usecase being "base" modules loaded by the startup module,
+ * such as jquery and the mw.loader client itself. These make use of
+ * ResourceLoaderModule and load.php for convenience but aren't actually
+ * registered in the startup module (as it would have to load itself).
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Timo Tijhof
+ */
+
+class ResourceLoaderRawFileModule extends ResourceLoaderFileModule {
+
+	/**
+	 * Enable raw mode to omit mw.loader.state() call as mw.loader
+	 * does not yet exist when these modules execute.
+	 * @var boolean
+	 */
+	protected $raw = true;
+
+	/**
+	 * Get all JavaScript code.
+	 *
+	 * @param ResourceLoaderContext $context
+	 * @return string JavaScript code
+	 */
+	public function getScript( ResourceLoaderContext $context ) {
+		$script = parent::getScript( $context );
+		// Add closure explicitly because raw modules can't be wrapped mw.loader.implement.
+		// Unlike with mw.loader.implement, this closure is immediately invoked.
+		// @see ResourceLoader::makeModuleResponse
+		// @see ResourceLoader::makeLoaderImplementScript
+		return "(function () {\n{$script}\n}());";
+	}
+}
diff --git a/includes/resourceloader/ResourceLoaderSiteModule.php b/includes/resourceloader/ResourceLoaderSiteModule.php
index 19e0baeb..380b7a53 100644
--- a/includes/resourceloader/ResourceLoaderSiteModule.php
+++ b/includes/resourceloader/ResourceLoaderSiteModule.php
@@ -47,13 +47,4 @@ class ResourceLoaderSiteModule extends ResourceLoaderWikiModule {
 		}
 		return $pages;
 	}
-
-	/**
-	 * Get group name
-	 *
-	 * @return string
-	 */
-	public function getGroup() {
-		return 'site';
-	}
 }
diff --git a/includes/resourceloader/ResourceLoaderSkinModule.php b/includes/resourceloader/ResourceLoaderSkinModule.php
index 3ba63e68..911d9534 100644
--- a/includes/resourceloader/ResourceLoaderSkinModule.php
+++ b/includes/resourceloader/ResourceLoaderSkinModule.php
@@ -44,13 +44,13 @@ class ResourceLoaderSkinModule extends ResourceLoaderFileModule {
 					'(min-resolution: 1.5dppx), ' .
 					'(min-resolution: 144dpi)'
 				][] = '.mw-wiki-logo { background-image: ' .
-				CSSMin::buildUrlValue( $logoHD['1.5x'] ) .';' .
+				CSSMin::buildUrlValue( $logoHD['1.5x'] ) . ';' .
 				'background-size: 135px auto; }';
 			}
 			if ( isset( $logoHD['2x'] ) ) {
 				$styles[
 					'(-webkit-min-device-pixel-ratio: 2), ' .
-					'(min--moz-device-pixel-ratio: 2),'.
+					'(min--moz-device-pixel-ratio: 2),' .
 					'(min-resolution: 2dppx), ' .
 					'(min-resolution: 192dpi)'
 				][] = '.mw-wiki-logo { background-image: ' .
@@ -73,15 +73,6 @@ class ResourceLoaderSkinModule extends ResourceLoaderFileModule {
 
 	/**
 	 * @param $context ResourceLoaderContext
-	 * @return int|mixed
-	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		$parentMTime = parent::getModifiedTime( $context );
-		return max( $parentMTime, $this->getHashMtime( $context ) );
-	}
-
-	/**
-	 * @param $context ResourceLoaderContext
 	 * @return string: Hash
 	 */
 	public function getModifiedHash( ResourceLoaderContext $context ) {
diff --git a/includes/resourceloader/ResourceLoaderSpecialCharacterDataModule.php b/includes/resourceloader/ResourceLoaderSpecialCharacterDataModule.php
index 5c917091..8170cb1c 100644
--- a/includes/resourceloader/ResourceLoaderSpecialCharacterDataModule.php
+++ b/includes/resourceloader/ResourceLoaderSpecialCharacterDataModule.php
@@ -35,7 +35,8 @@ class ResourceLoaderSpecialCharacterDataModule extends ResourceLoaderModule {
 	 * @return array
 	 */
 	protected function getData() {
-		return json_decode( file_get_contents( $this->path ) );
+		global $IP;
+		return json_decode( file_get_contents( "$IP/{$this->path}" ) );
 	}
 
 	/**
@@ -53,25 +54,17 @@ class ResourceLoaderSpecialCharacterDataModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int UNIX timestamp
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return static::safeFilemtime( $this->path );
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
 	 * @param ResourceLoaderContext $context
-	 * @return string Hash
-	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return md5( serialize( $this->getData() ) );
-	}
-
-	/**
 	 * @return array
 	 */
-	public function getDependencies() {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
 		return array( 'mediawiki.language' );
 	}
 
diff --git a/includes/resourceloader/ResourceLoaderStartUpModule.php b/includes/resourceloader/ResourceLoaderStartUpModule.php
index b2fbae9c..87d8ee20 100644
--- a/includes/resourceloader/ResourceLoaderStartUpModule.php
+++ b/includes/resourceloader/ResourceLoaderStartUpModule.php
@@ -24,14 +24,10 @@
 
 class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 
-	/* Protected Members */
-
-	protected $modifiedTime = array();
+	// Cache for getConfigSettings() as it's called by multiple methods
 	protected $configVars = array();
 	protected $targets = array( 'desktop', 'mobile' );
 
-	/* Protected Methods */
-
 	/**
 	 * @param ResourceLoaderContext $context
 	 * @return array
@@ -92,6 +88,7 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 			'wgContentNamespaces' => MWNamespace::getContentNamespaces(),
 			'wgSiteName' => $conf->get( 'Sitename' ),
 			'wgDBname' => $conf->get( 'DBname' ),
+			'wgExtraSignatureNamespaces' => $conf->get( 'ExtraSignatureNamespaces' ),
 			'wgAvailableSkins' => Skin::getSkinNames(),
 			'wgExtensionAssetsPath' => $conf->get( 'ExtensionAssetsPath' ),
 			// MediaWiki sets cookies to have this prefix by default
@@ -104,6 +101,9 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 			'wgLegalTitleChars' => Title::convertByteClassToUnicodeClass( Title::legalChars() ),
 			'wgResourceLoaderStorageVersion' => $conf->get( 'ResourceLoaderStorageVersion' ),
 			'wgResourceLoaderStorageEnabled' => $conf->get( 'ResourceLoaderStorageEnabled' ),
+			'wgResourceLoaderLegacyModules' => self::getLegacyModules(),
+			'wgForeignUploadTargets' => $conf->get( 'ForeignUploadTargets' ),
+			'wgEnableUploads' => $conf->get( 'EnableUploads' ),
 		);
 
 		Hooks::run( 'ResourceLoaderGetConfigVars', array( &$vars ) );
@@ -159,7 +159,7 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 	 * data send to the client.
 	 *
 	 * @param array &$registryData Modules keyed by name with properties:
-	 *  - number 'version'
+	 *  - string 'version'
 	 *  - array 'dependencies'
 	 *  - string|null 'group'
 	 *  - string 'source'
@@ -191,6 +191,9 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 
 		$resourceLoader = $context->getResourceLoader();
 		$target = $context->getRequest()->getVal( 'target', 'desktop' );
+		// Bypass target filter if this request is from a unit test context. To prevent misuse in
+		// production, this is only allowed if testing is enabled server-side.
+		$byPassTargetFilter = $this->getConfig()->get( 'EnableJavaScriptTest' ) && $target === 'test';
 
 		$out = '';
 		$registryData = array();
@@ -199,7 +202,7 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		foreach ( $resourceLoader->getModuleNames() as $name ) {
 			$module = $resourceLoader->getModule( $name );
 			$moduleTargets = $module->getTargets();
-			if ( !in_array( $target, $moduleTargets ) ) {
+			if ( !$byPassTargetFilter && !in_array( $target, $moduleTargets ) ) {
 				continue;
 			}
 
@@ -210,31 +213,27 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 				continue;
 			}
 
-			// Coerce module timestamp to UNIX timestamp.
-			// getModifiedTime() is supposed to return a UNIX timestamp, but custom implementations
-			// might forget. TODO: Maybe emit warning?
-			$moduleMtime = wfTimestamp( TS_UNIX, $module->getModifiedTime( $context ) );
+			$versionHash = $module->getVersionHash( $context );
+			if ( strlen( $versionHash ) !== 8 ) {
+				// Module implementation either broken or deviated from ResourceLoader::makeHash
+				// Asserted by tests/phpunit/structure/ResourcesTest.
+				$versionHash = ResourceLoader::makeHash( $versionHash );
+			}
 
 			$skipFunction = $module->getSkipFunction();
 			if ( $skipFunction !== null && !ResourceLoader::inDebugMode() ) {
 				$skipFunction = $resourceLoader->filter( 'minify-js',
 					$skipFunction,
-					// There will potentially be lots of these little string in the registrations
+					// There will potentially be lots of these little strings in the registrations
 					// manifest, we don't want to blow up the startup module with
-					// "/* cache key: ... */" all over it in non-debug mode.
+					// "/* cache key: ... */" all over it.
 					/* cacheReport = */ false
 				);
 			}
 
-			$mtime = max(
-				$moduleMtime,
-				wfTimestamp( TS_UNIX, $this->getConfig()->get( 'CacheEpoch' ) )
-			);
-
 			$registryData[$name] = array(
-				// Convert to numbers as wfTimestamp always returns a string, even for TS_UNIX
-				'version' => (int) $mtime,
-				'dependencies' => $module->getDependencies(),
+				'version' => $versionHash,
+				'dependencies' => $module->getDependencies( $context ),
 				'group' => $module->getGroup(),
 				'source' => $module->getSource(),
 				'loader' => $module->getLoaderScript(),
@@ -263,7 +262,7 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 				continue;
 			}
 
-			// Call mw.loader.register(name, timestamp, dependencies, group, source, skip)
+			// Call mw.loader.register(name, version, dependencies, group, source, skip)
 			$registrations[] = array(
 				$name,
 				$data['version'],
@@ -276,13 +275,11 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		}
 
 		// Register modules
-		$out .= ResourceLoader::makeLoaderRegisterScript( $registrations );
+		$out .= "\n" . ResourceLoader::makeLoaderRegisterScript( $registrations );
 
 		return $out;
 	}
 
-	/* Methods */
-
 	/**
 	 * @return bool
 	 */
@@ -299,6 +296,20 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		return array( 'jquery', 'mediawiki' );
 	}
 
+	public static function getLegacyModules() {
+		global $wgIncludeLegacyJavaScript, $wgPreloadJavaScriptMwUtil;
+
+		$legacyModules = array();
+		if ( $wgIncludeLegacyJavaScript ) {
+			$legacyModules[] = 'mediawiki.legacy.wikibits';
+		}
+		if ( $wgPreloadJavaScriptMwUtil ) {
+			$legacyModules[] = 'mediawiki.util';
+		}
+
+		return $legacyModules;
+	}
+
 	/**
 	 * Get the load URL of the startup modules.
 	 *
@@ -309,24 +320,16 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 	 * @return string
 	 */
 	public static function getStartupModulesUrl( ResourceLoaderContext $context ) {
+		$rl = $context->getResourceLoader();
 		$moduleNames = self::getStartupModules();
 
-		// Get the latest version
-		$loader = $context->getResourceLoader();
-		$version = 1;
-		foreach ( $moduleNames as $moduleName ) {
-			$version = max( $version,
-				$loader->getModule( $moduleName )->getModifiedTime( $context )
-			);
-		}
-
 		$query = array(
 			'modules' => ResourceLoader::makePackedModulesString( $moduleNames ),
 			'only' => 'scripts',
 			'lang' => $context->getLanguage(),
 			'skin' => $context->getSkin(),
 			'debug' => $context->getDebug() ? 'true' : 'false',
-			'version' => wfTimestamp( TS_ISO_8601_BASIC, $version )
+			'version' => $rl->getCombinedVersion( $context, $moduleNames ),
 		);
 		// Ensure uniform query order
 		ksort( $query );
@@ -339,40 +342,25 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 	 */
 	public function getScript( ResourceLoaderContext $context ) {
 		global $IP;
+		if ( $context->getOnly() !== 'scripts' ) {
+			return '/* Requires only=script */';
+		}
 
 		$out = file_get_contents( "$IP/resources/src/startup.js" );
-		if ( $context->getOnly() === 'scripts' ) {
 
-			// Startup function
-			$configuration = $this->getConfigSettings( $context );
-			$registrations = $this->getModuleRegistrations( $context );
+		$pairs = array_map( function ( $value ) {
+			$value = FormatJson::encode( $value, ResourceLoader::inDebugMode(), FormatJson::ALL_OK );
 			// Fix indentation
-			$registrations = str_replace( "\n", "\n\t", trim( $registrations ) );
-			$mwMapJsCall = Xml::encodeJsCall(
-				'mw.Map',
-				array( $this->getConfig()->get( 'LegacyJavaScriptGlobals' ) )
-			);
-			$mwConfigSetJsCall = Xml::encodeJsCall(
-				'mw.config.set',
-				array( $configuration ),
-				ResourceLoader::inDebugMode()
-			);
-
-			$out .= "var startUp = function () {\n" .
-				"\tmw.config = new " .
-				$mwMapJsCall . "\n" .
-				"\t$registrations\n" .
-				"\t" . $mwConfigSetJsCall .
-				"};\n";
-
-			// Conditional script injection
-			$scriptTag = Html::linkedScript( self::getStartupModulesUrl( $context ) );
-			$out .= "if ( isCompatible() ) {\n" .
-				"\t" . Xml::encodeJsCall( 'document.write', array( $scriptTag ) ) .
-				"\n}";
-		}
-
-		return $out;
+			$value = str_replace( "\n", "\n\t", $value );
+			return $value;
+		}, array(
+			'$VARS.wgLegacyJavaScriptGlobals' => $this->getConfig()->get( 'LegacyJavaScriptGlobals' ),
+			'$VARS.configuration' => $this->getConfigSettings( $context ),
+			'$VARS.baseModulesUri' => self::getStartupModulesUrl( $context ),
+		) );
+		$pairs['$CODE.registrations()'] = str_replace( "\n", "\n\t", trim( $this->getModuleRegistrations( $context ) ) );
+
+		return strtr( $out, $pairs );
 	}
 
 	/**
@@ -383,59 +371,48 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 	}
 
 	/**
+	 * Get the definition summary for this module.
+	 *
 	 * @param ResourceLoaderContext $context
-	 * @return array|mixed
+	 * @return array
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
+	public function getDefinitionSummary( ResourceLoaderContext $context ) {
 		global $IP;
+		$summary = parent::getDefinitionSummary( $context );
+		$summary[] = array(
+			// Detect changes to variables exposed in mw.config (T30899).
+			'vars' => $this->getConfigSettings( $context ),
+			// Changes how getScript() creates mw.Map for mw.config
+			'wgLegacyJavaScriptGlobals' => $this->getConfig()->get( 'LegacyJavaScriptGlobals' ),
+			// Detect changes to the module registrations
+			'moduleHashes' => $this->getAllModuleHashes( $context ),
 
-		$hash = $context->getHash();
-		if ( isset( $this->modifiedTime[$hash] ) ) {
-			return $this->modifiedTime[$hash];
-		}
-
-		// Call preloadModuleInfo() on ALL modules as we're about
-		// to call getModifiedTime() on all of them
-		$loader = $context->getResourceLoader();
-		$loader->preloadModuleInfo( $loader->getModuleNames(), $context );
-
-		$time = max(
-			wfTimestamp( TS_UNIX, $this->getConfig()->get( 'CacheEpoch' ) ),
-			filemtime( "$IP/resources/src/startup.js" ),
-			$this->getHashMtime( $context )
+			'fileMtimes' => array(
+				filemtime( "$IP/resources/src/startup.js" ),
+			),
 		);
-
-		// ATTENTION!: Because of the line below, this is not going to cause
-		// infinite recursion - think carefully before making changes to this
-		// code!
-		// Pre-populate modifiedTime with something because the loop over
-		// all modules below includes the startup module (this module).
-		$this->modifiedTime[$hash] = 1;
-
-		foreach ( $loader->getModuleNames() as $name ) {
-			$module = $loader->getModule( $name );
-			$time = max( $time, $module->getModifiedTime( $context ) );
-		}
-
-		$this->modifiedTime[$hash] = $time;
-		return $this->modifiedTime[$hash];
+		return $summary;
 	}
 
 	/**
-	 * Hash of all dynamic data embedded in getScript().
-	 *
-	 * Detect changes to mw.config settings embedded in #getScript (bug 28899).
+	 * Helper method for getDefinitionSummary().
 	 *
 	 * @param ResourceLoaderContext $context
-	 * @return string Hash
+	 * @return string SHA-1
 	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		$data = array(
-			'vars' => $this->getConfigSettings( $context ),
-			'wgLegacyJavaScriptGlobals' => $this->getConfig()->get( 'LegacyJavaScriptGlobals' ),
-		);
-
-		return md5( serialize( $data ) );
+	protected function getAllModuleHashes( ResourceLoaderContext $context ) {
+		$rl = $context->getResourceLoader();
+		// Preload for getCombinedVersion()
+		$rl->preloadModuleInfo( $rl->getModuleNames(), $context );
+
+		// ATTENTION: Because of the line below, this is not going to cause infinite recursion.
+		// Think carefully before making changes to this code!
+		// Pre-populate versionHash with something because the loop over all modules below includes
+		// the startup module (this module).
+		// See ResourceLoaderModule::getVersionHash() for usage of this cache.
+		$this->versionHash[$context->getHash()] = null;
+
+		return $rl->getCombinedVersion( $context, $rl->getModuleNames() );
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderUserCSSPrefsModule.php b/includes/resourceloader/ResourceLoaderUserCSSPrefsModule.php
index 472ceb26..65d770e2 100644
--- a/includes/resourceloader/ResourceLoaderUserCSSPrefsModule.php
+++ b/includes/resourceloader/ResourceLoaderUserCSSPrefsModule.php
@@ -27,25 +27,13 @@
  */
 class ResourceLoaderUserCSSPrefsModule extends ResourceLoaderModule {
 
-	/* Protected Members */
-
-	protected $modifiedTime = array();
-
 	protected $origin = self::ORIGIN_CORE_INDIVIDUAL;
 
-	/* Methods */
-
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return array|int|mixed
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		$hash = $context->getHash();
-		if ( !isset( $this->modifiedTime[$hash] ) ) {
-			$this->modifiedTime[$hash] = wfTimestamp( TS_UNIX, $context->getUserObj()->getTouched() );
-		}
-
-		return $this->modifiedTime[$hash];
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderUserDefaultsModule.php b/includes/resourceloader/ResourceLoaderUserDefaultsModule.php
index 5f4bc16b..eba61edc 100644
--- a/includes/resourceloader/ResourceLoaderUserDefaultsModule.php
+++ b/includes/resourceloader/ResourceLoaderUserDefaultsModule.php
@@ -26,26 +26,13 @@
  */
 class ResourceLoaderUserDefaultsModule extends ResourceLoaderModule {
 
-	/* Protected Members */
-
 	protected $targets = array( 'desktop', 'mobile' );
 
-	/* Methods */
-
-	/**
-	 * @param ResourceLoaderContext $context
-	 * @return string Hash
-	 */
-	public function getModifiedHash( ResourceLoaderContext $context ) {
-		return md5( serialize( User::getDefaultOptions() ) );
-	}
-
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		return $this->getHashMtime( $context );
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderUserOptionsModule.php b/includes/resourceloader/ResourceLoaderUserOptionsModule.php
index 84c1906d..0847109c 100644
--- a/includes/resourceloader/ResourceLoaderUserOptionsModule.php
+++ b/includes/resourceloader/ResourceLoaderUserOptionsModule.php
@@ -27,34 +27,23 @@
  */
 class ResourceLoaderUserOptionsModule extends ResourceLoaderModule {
 
-	/* Protected Members */
-
-	protected $modifiedTime = array();
-
 	protected $origin = self::ORIGIN_CORE_INDIVIDUAL;
 
 	protected $targets = array( 'desktop', 'mobile' );
 
-	/* Methods */
-
 	/**
+	 * @param ResourceLoaderContext $context
 	 * @return array List of module names as strings
 	 */
-	public function getDependencies() {
+	public function getDependencies( ResourceLoaderContext $context = null ) {
 		return array( 'user.defaults' );
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		$hash = $context->getHash();
-		if ( !isset( $this->modifiedTime[$hash] ) ) {
-			$this->modifiedTime[$hash] = wfTimestamp( TS_UNIX, $context->getUserObj()->getTouched() );
-		}
-
-		return $this->modifiedTime[$hash];
+	public function enableModuleContentVersion() {
+		return true;
 	}
 
 	/**
diff --git a/includes/resourceloader/ResourceLoaderWikiModule.php b/includes/resourceloader/ResourceLoaderWikiModule.php
index 7b44cc67..0023de27 100644
--- a/includes/resourceloader/ResourceLoaderWikiModule.php
+++ b/includes/resourceloader/ResourceLoaderWikiModule.php
@@ -26,15 +26,30 @@
  * Abstraction for resource loader modules which pull from wiki pages
  *
  * This can only be used for wiki pages in the MediaWiki and User namespaces,
- * because of its dependence on the functionality of
- * Title::isCssJsSubpage.
+ * because of its dependence on the functionality of Title::isCssJsSubpage.
+ *
+ * This module supports being used as a placeholder for a module on a remote wiki.
+ * To do so, getDB() must be overloaded to return a foreign database object that
+ * allows local wikis to query page metadata.
+ *
+ * Safe for calls on local wikis are:
+ * - Option getters:
+ *   - getGroup()
+ *   - getPosition()
+ *   - getPages()
+ * - Basic methods that strictly involve the foreign database
+ *   - getDB()
+ *   - isKnownEmpty()
+ *   - getTitleInfo()
  */
 class ResourceLoaderWikiModule extends ResourceLoaderModule {
+	/** @var string Position on the page to load this module at */
+	protected $position = 'bottom';
 
 	// Origin defaults to users with sitewide authority
 	protected $origin = self::ORIGIN_USER_SITEWIDE;
 
-	// In-object cache for title info
+	// In-process cache for title info
 	protected $titleInfo = array();
 
 	// List of page names that contain CSS
@@ -50,14 +65,21 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 	 * @param array $options For back-compat, this can be omitted in favour of overwriting getPages.
 	 */
 	public function __construct( array $options = null ) {
-		if ( isset( $options['styles'] ) ) {
-			$this->styles = $options['styles'];
+		if ( is_null( $options ) ) {
+			return;
 		}
-		if ( isset( $options['scripts'] ) ) {
-			$this->scripts = $options['scripts'];
-		}
-		if ( isset( $options['group'] ) ) {
-			$this->group = $options['group'];
+
+		foreach ( $options as $member => $option ) {
+			switch ( $member ) {
+				case 'position':
+					$this->isPositionDefined = true;
+					// Don't break since we need the member set as well
+				case 'styles':
+				case 'scripts':
+				case 'group':
+					$this->{$member} = $option;
+					break;
+			}
 		}
 	}
 
@@ -107,13 +129,13 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * Get the Database object used in getTitleMTimes(). Defaults to the local slave DB
-	 * but subclasses may want to override this to return a remote DB object, or to return
-	 * null if getTitleMTimes() shouldn't access the DB at all.
+	 * Get the Database object used in getTitleInfo().
+	 *
+	 * Defaults to the local slave DB. Subclasses may want to override this to return a foreign
+	 * database object, or null if getTitleInfo() shouldn't access the database.
 	 *
-	 * NOTE: This ONLY works for getTitleMTimes() and getModifiedTime(), NOT FOR ANYTHING ELSE.
-	 * In particular, it doesn't work for getting the content of JS and CSS pages. That functionality
-	 * will use the local DB irrespective of the return value of this method.
+	 * NOTE: This ONLY works for getTitleInfo() and isKnownEmpty(), NOT FOR ANYTHING ELSE.
+	 * In particular, it doesn't work for getContent() or getScript() etc.
 	 *
 	 * @return IDatabase|null
 	 */
@@ -122,10 +144,15 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * @param Title $title
+	 * @param string $title
 	 * @return null|string
 	 */
-	protected function getContent( $title ) {
+	protected function getContent( $titleText ) {
+		$title = Title::newFromText( $titleText );
+		if ( !$title ) {
+			return null;
+		}
+
 		$handler = ContentHandler::getForTitle( $title );
 		if ( $handler->isSupportedFormat( CONTENT_FORMAT_CSS ) ) {
 			$format = CONTENT_FORMAT_CSS;
@@ -160,11 +187,7 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 			if ( $options['type'] !== 'script' ) {
 				continue;
 			}
-			$title = Title::newFromText( $titleText );
-			if ( !$title || $title->isRedirect() ) {
-				continue;
-			}
-			$script = $this->getContent( $title );
+			$script = $this->getContent( $titleText );
 			if ( strval( $script ) !== '' ) {
 				$script = $this->validateScriptFile( $titleText, $script );
 				$scripts .= ResourceLoader::makeComment( $titleText ) . $script . "\n";
@@ -183,12 +206,8 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 			if ( $options['type'] !== 'style' ) {
 				continue;
 			}
-			$title = Title::newFromText( $titleText );
-			if ( !$title || $title->isRedirect() ) {
-				continue;
-			}
 			$media = isset( $options['media'] ) ? $options['media'] : 'all';
-			$style = $this->getContent( $title );
+			$style = $this->getContent( $titleText );
 			if ( strval( $style ) === '' ) {
 				continue;
 			}
@@ -206,37 +225,31 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 	}
 
 	/**
-	 * @param ResourceLoaderContext $context
-	 * @return int
+	 * Disable module content versioning.
+	 *
+	 * This class does not support generating content outside of a module
+	 * request due to foreign database support.
+	 *
+	 * See getDefinitionSummary() for meta-data versioning.
+	 *
+	 * @return bool
 	 */
-	public function getModifiedTime( ResourceLoaderContext $context ) {
-		$modifiedTime = 1;
-		$titleInfo = $this->getTitleInfo( $context );
-		if ( count( $titleInfo ) ) {
-			$mtimes = array_map( function ( $value ) {
-				return $value['timestamp'];
-			}, $titleInfo );
-			$modifiedTime = max( $modifiedTime, max( $mtimes ) );
-		}
-		$modifiedTime = max(
-			$modifiedTime,
-			$this->getMsgBlobMtime( $context->getLanguage() ),
-			$this->getDefinitionMtime( $context )
-		);
-		return $modifiedTime;
+	public function enableModuleContentVersion() {
+		return false;
 	}
 
 	/**
-	 * Get the definition summary for this module.
-	 *
 	 * @param ResourceLoaderContext $context
 	 * @return array
 	 */
 	public function getDefinitionSummary( ResourceLoaderContext $context ) {
-		return array(
-			'class' => get_class( $this ),
+		$summary = parent::getDefinitionSummary( $context );
+		$summary[] = array(
 			'pages' => $this->getPages( $context ),
+			// Includes SHA1 of content
+			'titleInfo' => $this->getTitleInfo( $context ),
 		);
+		return $summary;
 	}
 
 	/**
@@ -244,33 +257,29 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 	 * @return bool
 	 */
 	public function isKnownEmpty( ResourceLoaderContext $context ) {
-		$titleInfo = $this->getTitleInfo( $context );
-		// Bug 68488: For modules in the "user" group, we should actually
-		// check that the pages are empty (page_len == 0), but for other
-		// groups, just check the pages exist so that we don't end up
-		// caching temporarily-blank pages without the appropriate
-		// <script> or <link> tag.
-		if ( $this->getGroup() !== 'user' ) {
-			return count( $titleInfo ) === 0;
-		}
+		$revisions = $this->getTitleInfo( $context );
 
-		foreach ( $titleInfo as $info ) {
-			if ( $info['length'] !== 0 ) {
-				// At least one non-0-lenth page, not empty
-				return false;
+		// For user modules, don't needlessly load if there are no non-empty pages
+		if ( $this->getGroup() === 'user' ) {
+			foreach ( $revisions as $revision ) {
+				if ( $revision['rev_len'] > 0 ) {
+					// At least one non-empty page, module should be loaded
+					return false;
+				}
 			}
+			return true;
 		}
 
-		// All pages are 0-length, so it's empty
-		return true;
+		// Bug 68488: For other modules (i.e. ones that are called in cached html output) only check
+		// page existance. This ensures that, if some pages in a module are temporarily blanked,
+		// we don't end omit the module's script or link tag on some pages.
+		return count( $revisions ) === 0;
 	}
 
 	/**
-	 * Get the modification times of all titles that would be loaded for
-	 * a given context.
-	 * @param ResourceLoaderContext $context Context object
-	 * @return array Keyed by page dbkey. Value is an array with 'length' and 'timestamp'
-	 *               keys, where the timestamp is a UNIX timestamp
+	 * Get the information about the wiki pages for a given context.
+	 * @param ResourceLoaderContext $context
+	 * @return array Keyed by page name. Contains arrays with 'rev_len' and 'rev_sha1' keys
 	 */
 	protected function getTitleInfo( ResourceLoaderContext $context ) {
 		$dbr = $this->getDB();
@@ -279,31 +288,38 @@ class ResourceLoaderWikiModule extends ResourceLoaderModule {
 			return array();
 		}
 
-		$hash = $context->getHash();
-		if ( isset( $this->titleInfo[$hash] ) ) {
-			return $this->titleInfo[$hash];
-		}
-
-		$this->titleInfo[$hash] = array();
-		$batch = new LinkBatch;
-		foreach ( $this->getPages( $context ) as $titleText => $options ) {
-			$batch->addObj( Title::newFromText( $titleText ) );
-		}
+		$pages = $this->getPages( $context );
+		$key = implode( '|', array_keys( $pages ) );
+		if ( !isset( $this->titleInfo[$key] ) ) {
+			$this->titleInfo[$key] = array();
+			$batch = new LinkBatch;
+			foreach ( $pages as $titleText => $options ) {
+				$batch->addObj( Title::newFromText( $titleText ) );
+			}
 
-		if ( !$batch->isEmpty() ) {
-			$res = $dbr->select( 'page',
-				array( 'page_namespace', 'page_title', 'page_touched', 'page_len' ),
-				$batch->constructSet( 'page', $dbr ),
-				__METHOD__
-			);
-			foreach ( $res as $row ) {
-				$title = Title::makeTitle( $row->page_namespace, $row->page_title );
-				$this->titleInfo[$hash][$title->getPrefixedDBkey()] = array(
-					'timestamp' => wfTimestamp( TS_UNIX, $row->page_touched ),
-					'length' => $row->page_len,
+			if ( !$batch->isEmpty() ) {
+				$res = $dbr->select( array( 'page', 'revision' ),
+					array( 'page_namespace', 'page_title', 'rev_len', 'rev_sha1' ),
+					$batch->constructSet( 'page', $dbr ),
+					__METHOD__,
+					array(),
+					array( 'revision' => array( 'INNER JOIN', array( 'page_latest=rev_id' ) ) )
 				);
+				foreach ( $res as $row ) {
+					// Avoid including ids or timestamps of revision/page tables so
+					// that versions are not wasted
+					$title = Title::makeTitle( $row->page_namespace, $row->page_title );
+					$this->titleInfo[$key][$title->getPrefixedText()] = array(
+						'rev_len' => $row->rev_len,
+						'rev_sha1' => $row->rev_sha1,
+					);
+				}
 			}
 		}
-		return $this->titleInfo[$hash];
+		return $this->titleInfo[$key];
+	}
+
+	public function getPosition() {
+		return $this->position;
 	}
 }