mediawiki.loader.js
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mediawiki.loader.js
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	/*!
	* Defines mw.loader, the infrastructure for loading ResourceLoader
	* modules.
	*
	* This file is appended directly to the code in startup/mediawiki.js
	*/
	/* global $VARS, $CODE, mw */

	( function () {
	'use strict';

	var store,
	hasOwn = Object.hasOwnProperty;

	/**
	* Client for ResourceLoader server end point.
	*
	* This client is in charge of maintaining the module registry and state
	* machine, initiating network (batch) requests for loading modules, as
	* well as dependency resolution and execution of source code.
	*
	* @see <https://www.mediawiki.org/wiki/ResourceLoader/Features>
	* @namespace mw.loader
	*/

	/**
	* FNV132 hash function
	*
	* This function implements the 32-bit version of FNV-1.
	* It is equivalent to hash( 'fnv132', ... ) in PHP, except
	* its output is base 36 rather than hex.
	* See <https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function>
	*
	* @private
	* @param {string} str String to hash
	* @return {string} hash as a five-character base 36 string
	*/
	function fnv132( str ) {
	var hash = 0x811C9DC5;

	/* eslint-disable no-bitwise */
	for ( var i = 0; i < str.length; i++ ) {
	hash += ( hash << 1 ) + ( hash << 4 ) + ( hash << 7 ) + ( hash << 8 ) + ( hash << 24 );
	hash ^= str.charCodeAt( i );
	}

	hash = ( hash >>> 0 ).toString( 36 ).slice( 0, 5 );
	/* eslint-enable no-bitwise */

	while ( hash.length < 5 ) {
	hash = '0' + hash;
	}
	return hash;
	}

	/**
	* Fired via mw.track on various resource loading errors.
	*
	* eslint-disable jsdoc/valid-types
	*
	* @event ~'resourceloader.exception'
	* @ignore
	* @param {Error\|Mixed} e The error that was thrown. Almost always an Error
	* object, but in theory module code could manually throw something else, and that
	* might also end up here.
	* @param {string} [module] Name of the module which caused the error. Omitted if the
	* error is not module-related or the module cannot be easily identified due to
	* batched handling.
	* @param {string} source Source of the error. Possible values:
	*
	* - load-callback: exception thrown by user callback
	* - module-execute: exception thrown by module code
	* - resolve: failed to sort dependencies for a module in mw.loader.load
	* - store-eval: could not evaluate module code cached in localStorage
	* - store-localstorage-json: JSON conversion error in mw.loader.store
	* - store-localstorage-update: localStorage conversion error in mw.loader.store.
	*/

	/**
	* Mapping of registered modules.
	*
	* See #implement and #execute for exact details on support for script, style and messages.
	*
	* @example // Format:
	* {
	* 'moduleName': {
	* // From mw.loader.register()
	* 'version': '#####' (five-character hash)
	* 'dependencies': ['required.foo', 'bar.also', ...]
	* 'group': string, integer, (or) null
	* 'source': 'local', (or) 'anotherwiki'
	* 'skip': 'return !!window.Example;', (or) null, (or) boolean result of skip
	* 'module': export Object
	*
	* // Set by execute() or mw.loader.state()
	* // See mw.loader.getState() for documentation of the state machine
	* 'state': 'registered', 'loading', 'loaded', 'executing', 'ready', 'error', or 'missing'
	*
	* // Optionally added at run-time by mw.loader.impl()
	* 'script': closure, array of urls, or string
	* 'style': { ... } (see #execute)
	* 'messages': { 'key': 'value', ... }
	* }
	* }
	*
	* @property {Object}
	* @private
	*/
	var registry = Object.create( null ),
	// Mapping of sources, keyed by source-id, values are strings.
	//
	// Format:
	//
	// {
	// 'sourceId': 'http://example.org/w/load.php'
	// }
	//
	sources = Object.create( null ),

	// For queueModuleScript()
	handlingPendingRequests = false,
	pendingRequests = [],

	// List of modules to be loaded
	queue = [],

	/**
	* List of callback jobs waiting for modules to be ready.
	*
	* Jobs are created by #enqueue() and run by #doPropagation().
	* Typically when a job is created for a module, the job's dependencies contain
	* both the required module and all its recursive dependencies.
	*
	* @example // Format:
	* {
	* 'dependencies': [ module names ],
	* 'ready': Function callback
	* 'error': Function callback
	* }
	*
	* @property {Object[]} jobs
	* @private
	*/
	jobs = [],

	// For #setAndPropagate() and #doPropagation()
	willPropagate = false,
	errorModules = [],

	/**
	* @private
	* @property {Array} baseModules
	*/
	baseModules = $VARS.baseModules,

	/**
	* For #addEmbeddedCSS() and #addLink()
	*
	* @private
	* @property {HTMLElement\|null} marker
	*/
	marker = document.querySelector( 'meta[name="ResourceLoaderDynamicStyles"]' ),

	// For #addEmbeddedCSS()
	lastCssBuffer;

	/**
	* Append an HTML element to `document.head` or before a specified node.
	*
	* @private
	* @param {HTMLElement} el
	* @param {Node\|null} [nextNode]
	*/
	function addToHead( el, nextNode ) {
	if ( nextNode && nextNode.parentNode ) {
	nextNode.parentNode.insertBefore( el, nextNode );
	} else {
	document.head.appendChild( el );
	}
	}

	/**
	* Create a new style element and add it to the DOM.
	* Stable for use in gadgets.
	*
	* @method mw.loader.addStyleTag
	* @param {string} text CSS text
	* @param {Node\|null} [nextNode] The element where the style tag
	* should be inserted before
	* @return {HTMLStyleElement} Reference to the created style element
	*/
	function newStyleTag( text, nextNode ) {
	var el = document.createElement( 'style' );
	el.appendChild( document.createTextNode( text ) );
	addToHead( el, nextNode );
	return el;
	}

	/**
	* @private
	* @param {Object} cssBuffer
	*/
	function flushCssBuffer( cssBuffer ) {
	// Make sure the next call to addEmbeddedCSS() starts a new buffer.
	// This must be done before we run the callbacks, as those may end up
	// queueing new chunks which would be lost otherwise (T105973).
	//
	// There can be more than one buffer in-flight (given "@import", and
	// generally due to race conditions). Only tell addEmbeddedCSS() to
	// start a new buffer if we're currently flushing the last one that it
	// started. If we're flushing an older buffer, keep the last one open.
	if ( cssBuffer === lastCssBuffer ) {
	lastCssBuffer = null;
	}
	newStyleTag( cssBuffer.cssText, marker );
	for ( var i = 0; i < cssBuffer.callbacks.length; i++ ) {
	cssBuffer.callbacks[ i ]();
	}
	}

	/**
	* Add a bit of CSS text to the current browser page.
	*
	* The creation and insertion of the `<style>` element is debounced for two reasons:
	*
	* - Performing the insertion before the next paint round via requestAnimationFrame
	* avoids forced or wasted style recomputations, which are expensive in browsers.
	* - Reduce how often new stylesheets are inserted by letting additional calls to this
	* function accumulate into a buffer for at least one JavaScript tick. Modules are
	* received from the server in batches, which means there is likely going to be many
	* calls to this function in a row within the same tick / the same call stack.
	* See also T47810.
	*
	* @private
	* @param {string} cssText CSS text to be added in a `<style>` tag.
	* @param {Function} callback Called after the insertion has occurred.
	*/
	function addEmbeddedCSS( cssText, callback ) {
	// Start a new buffer if one of the following is true:
	// - We've never started a buffer before, this will be our first.
	// - The last buffer we created was flushed meanwhile, so start a new one.
	// - The next CSS chunk syntactically needs to be at the start of a stylesheet (T37562).
	if ( !lastCssBuffer \|\| cssText.startsWith( '@import' ) ) {
	lastCssBuffer = {
	cssText: '',
	callbacks: []
	};
	requestAnimationFrame( flushCssBuffer.bind( null, lastCssBuffer ) );
	}

	// Linebreak for somewhat distinguishable sections
	lastCssBuffer.cssText += '\n' + cssText;
	lastCssBuffer.callbacks.push( callback );
	}

	/**
	* See also `ResourceLoader.php#makeVersionQuery` on the server.
	*
	* @private
	* @param {string[]} modules List of module names
	* @return {string} Hash of concatenated version hashes.
	*/
	function getCombinedVersion( modules ) {
	var hashes = modules.reduce( function ( result, module ) {
	return result + registry[ module ].version;
	}, '' );
	return fnv132( hashes );
	}

	/**
	* Determine whether all dependencies are in state 'ready', which means we may
	* execute the module or job now.
	*
	* @private
	* @param {string[]} modules Names of modules to be checked
	* @return {boolean} True if all modules are in state 'ready', false otherwise
	*/
	function allReady( modules ) {
	for ( var i = 0; i < modules.length; i++ ) {
	if ( mw.loader.getState( modules[ i ] ) !== 'ready' ) {
	return false;
	}
	}
	return true;
	}

	/**
	* Determine whether all direct and base dependencies are in state 'ready'
	*
	* @private
	* @param {string} module Name of the module to be checked
	* @return {boolean} True if all direct/base dependencies are in state 'ready'; false otherwise
	*/
	function allWithImplicitReady( module ) {
	return allReady( registry[ module ].dependencies ) &&
	( baseModules.indexOf( module ) !== -1 \|\| allReady( baseModules ) );
	}

	/**
	* Determine whether all dependencies are in state 'ready', which means we may
	* execute the module or job now.
	*
	* @private
	* @param {string[]} modules Names of modules to be checked
	* @return {boolean\|string} False if no modules are in state 'error' or 'missing';
	* failed module otherwise
	*/
	function anyFailed( modules ) {
	for ( var i = 0; i < modules.length; i++ ) {
	var state = mw.loader.getState( modules[ i ] );
	if ( state === 'error' \|\| state === 'missing' ) {
	return modules[ i ];
	}
	}
	return false;
	}

	/**
	* Handle propagation of module state changes and reactions to them.
	*
	* - When a module reaches a failure state, this should be propagated to
	* modules that depend on the failed module.
	* - When a module reaches a final state, pending job callbacks for the
	* module from mw.loader.using() should be called.
	* - When a module reaches the 'ready' state from #execute(), consider
	* executing dependent modules now having their dependencies satisfied.
	* - When a module reaches the 'loaded' state from mw.loader.impl,
	* consider executing it, if it has no unsatisfied dependencies.
	*
	* @private
	*/
	function doPropagation() {
	var didPropagate = true;
	var module;

	// Keep going until the last iteration performed no actions.
	while ( didPropagate ) {
	didPropagate = false;

	// Stage 1: Propagate failures
	while ( errorModules.length ) {
	var errorModule = errorModules.shift(),
	baseModuleError = baseModules.indexOf( errorModule ) !== -1;
	for ( module in registry ) {
	if ( registry[ module ].state !== 'error' && registry[ module ].state !== 'missing' ) {
	if ( baseModuleError && baseModules.indexOf( module ) === -1 ) {
	// Propate error from base module to all regular (non-base) modules
	registry[ module ].state = 'error';
	didPropagate = true;
	} else if ( registry[ module ].dependencies.indexOf( errorModule ) !== -1 ) {
	// Propagate error from dependency to depending module
	registry[ module ].state = 'error';
	// .. and propagate it further
	errorModules.push( module );
	didPropagate = true;
	}
	}
	}
	}

	// Stage 2: Execute 'loaded' modules with no unsatisfied dependencies
	for ( module in registry ) {
	if ( registry[ module ].state === 'loaded' && allWithImplicitReady( module ) ) {
	// Recursively execute all dependent modules that were already loaded
	// (waiting for execution) and no longer have unsatisfied dependencies.
	// Base modules may have dependencies amongst eachother to ensure correct
	// execution order. Regular modules wait for all base modules.
	execute( module );
	didPropagate = true;
	}
	}

	// Stage 3: Invoke job callbacks that are no longer blocked
	for ( var i = 0; i < jobs.length; i++ ) {
	var job = jobs[ i ];
	var failed = anyFailed( job.dependencies );
	if ( failed !== false \|\| allReady( job.dependencies ) ) {
	jobs.splice( i, 1 );
	i -= 1;
	try {
	if ( failed !== false && job.error ) {
	job.error( new Error( 'Failed dependency: ' + failed ), job.dependencies );
	} else if ( failed === false && job.ready ) {
	job.ready();
	}
	} catch ( e ) {
	// A user-defined callback raised an exception.
	// Swallow it to protect our state machine!
	mw.trackError( {
	exception: e,
	source: 'load-callback'
	} );
	}
	didPropagate = true;
	}
	}
	}

	willPropagate = false;
	}

	/**
	* Update a module's state in the registry and make sure any necessary
	* propagation will occur, by adding a (debounced) call to doPropagation().
	* See #doPropagation for more about propagation.
	* See #registry for more about how states are used.
	*
	* @private
	* @param {string} module
	* @param {string} state
	*/
	function setAndPropagate( module, state ) {
	registry[ module ].state = state;
	if ( state === 'ready' ) {
	// Queue to later be synced to the local module store.
	store.add( module );
	} else if ( state === 'error' \|\| state === 'missing' ) {
	errorModules.push( module );
	} else if ( state !== 'loaded' ) {
	// We only have something to do in doPropagation for the
	// 'loaded', 'ready', 'error', and 'missing' states.
	// Avoid scheduling and propagation cost for frequent and short-lived
	// transition states, such as 'loading' and 'executing'.
	return;
	}
	if ( willPropagate ) {
	// Already scheduled, or, we're already in a doPropagation stack.
	return;
	}
	willPropagate = true;
	// Yield for two reasons:
	// * Allow successive calls to mw.loader.impl() from the same
	// load.php response, or from the same asyncEval() to be in the
	// propagation batch.
	// * Allow the browser to breathe between the reception of
	// module source code and the execution of it.
	//
	// Use a high priority because the user may be waiting for interactions
	// to start being possible. But, first provide a moment (up to 'timeout')
	// for native input event handling (e.g. scrolling/typing/clicking).
	mw.requestIdleCallback( doPropagation, { timeout: 1 } );
	}

	/**
	* Resolve dependencies and detect circular references.
	*
	* @private
	* @param {string} module Name of the top-level module whose dependencies shall be
	* resolved and sorted.
	* @param {Array} resolved Returns a topological sort of the given module and its
	* dependencies, such that later modules depend on earlier modules. The array
	* contains the module names. If the array contains already some module names,
	* this function appends its result to the pre-existing array.
	* @param {Set} [unresolved] Used to detect loops in the dependency graph.
	* @throws {Error} If an unknown module or a circular dependency is encountered
	*/
	function sortDependencies( module, resolved, unresolved ) {
	if ( !( module in registry ) ) {
	throw new Error( 'Unknown module: ' + module );
	}

	if ( typeof registry[ module ].skip === 'string' ) {
	// eslint-disable-next-line no-new-func
	var skip = ( new Function( registry[ module ].skip )() );
	registry[ module ].skip = !!skip;
	if ( skip ) {
	registry[ module ].dependencies = [];
	setAndPropagate( module, 'ready' );
	return;
	}
	}

	// Create unresolved if not passed in
	if ( !unresolved ) {
	unresolved = new Set();
	}

	// Track down dependencies
	var deps = registry[ module ].dependencies;
	unresolved.add( module );
	for ( var i = 0; i < deps.length; i++ ) {
	if ( resolved.indexOf( deps[ i ] ) === -1 ) {
	if ( unresolved.has( deps[ i ] ) ) {
	throw new Error(
	'Circular reference detected: ' + module + ' -> ' + deps[ i ]
	);
	}

	sortDependencies( deps[ i ], resolved, unresolved );
	}
	}

	resolved.push( module );
	}

	/**
	* Get names of module that a module depends on, in their proper dependency order.
	*
	* @private
	* @param {string[]} modules Array of string module names
	* @return {Array} List of dependencies, including 'module'.
	* @throws {Error} If an unregistered module or a dependency loop is encountered
	*/
	function resolve( modules ) {
	// Always load base modules
	var resolved = baseModules.slice();
	for ( var i = 0; i < modules.length; i++ ) {
	sortDependencies( modules[ i ], resolved );
	}
	return resolved;
	}

	/**
	* Like #resolve(), except it will silently ignore modules that
	* are missing or have missing dependencies.
	*
	* @private
	* @param {string[]} modules Array of string module names
	* @return {Array} List of dependencies.
	*/
	function resolveStubbornly( modules ) {
	// Always load base modules
	var resolved = baseModules.slice();
	for ( var i = 0; i < modules.length; i++ ) {
	var saved = resolved.slice();
	try {
	sortDependencies( modules[ i ], resolved );
	} catch ( err ) {
	resolved = saved;
	// This module is not currently known, or has invalid dependencies.
	//
	// Most likely due to a cached reference after the module was
	// removed, otherwise made redundant, or omitted from the registry
	// by the ResourceLoader "target" system.
	//
	// These errors can be common, e.g. queuing an unavailable module
	// unconditionally from the server-side is OK and should fail gracefully.
	mw.log.warn( 'Skipped unavailable module ' + modules[ i ] );

	// Do not track this error as an exception when the module:
	// - Is valid, but gracefully filtered out by target system.
	// - Was recently valid, but is still referenced in stale cache.
	//
	// Basically the only reason to track this as exception is when the error
	// was circular or invalid dependencies. What the above scenarios have in
	// common is that they don't register the module client-side.
	if ( modules[ i ] in registry ) {
	mw.trackError( {
	exception: err,
	source: 'resolve'
	} );
	}
	}
	}
	return resolved;
	}

	/**
	* Resolve a relative file path.
	*
	* For example, resolveRelativePath( '../foo.js', 'resources/src/bar/bar.js' )
	* returns 'resources/src/foo.js'.
	*
	* @private
	* @param {string} relativePath Relative file path, starting with ./ or ../
	* @param {string} basePath Path of the file (not directory) relativePath is relative to
	* @return {string\|null} Resolved path, or null if relativePath does not start with ./ or ../
	*/
	function resolveRelativePath( relativePath, basePath ) {

	var relParts = relativePath.match( /^((?:\.\.?\/)+)(.*)$/ );
	if ( !relParts ) {
	return null;
	}

	var baseDirParts = basePath.split( '/' );
	// basePath looks like 'foo/bar/baz.js', so baseDirParts looks like [ 'foo', 'bar, 'baz.js' ]
	// Remove the file component at the end, so that we are left with only the directory path
	baseDirParts.pop();

	var prefixes = relParts[ 1 ].split( '/' );
	// relParts[ 1 ] looks like '../../', so prefixes looks like [ '..', '..', '' ]
	// Remove the empty element at the end
	prefixes.pop();

	// For every ../ in the path prefix, remove one directory level from baseDirParts
	var prefix;
	var reachedRoot = false;
	while ( ( prefix = prefixes.pop() ) !== undefined ) {
	if ( prefix === '..' ) {
	// Once we reach the package's base dir, preserve all remaining "..".
	reachedRoot = !baseDirParts.length \|\| reachedRoot;
	if ( !reachedRoot ) {
	baseDirParts.pop();
	} else {
	baseDirParts.push( prefix );
	}
	}
	}

	// If there's anything left of the base path, prepend it to the file path
	return ( baseDirParts.length ? baseDirParts.join( '/' ) + '/' : '' ) + relParts[ 2 ];
	}

	/**
	* Make a require() function scoped to a package file
	*
	* @private
	* @param {Object} moduleObj Module object from the registry
	* @param {string} basePath Path of the file this is scoped to. Used for relative paths.
	* @return {Function}
	*/
	function makeRequireFunction( moduleObj, basePath ) {
	return function require( moduleName ) {
	var fileName = resolveRelativePath( moduleName, basePath );
	if ( fileName === null ) {
	// Not a relative path, so it's either a module name or,
	// (if in test mode) a private file imported from another module.
	return mw.loader.require( moduleName );
	}

	if ( hasOwn.call( moduleObj.packageExports, fileName ) ) {
	// File has already been executed, return the cached result
	return moduleObj.packageExports[ fileName ];
	}

	var scriptFiles = moduleObj.script.files;
	if ( !hasOwn.call( scriptFiles, fileName ) ) {
	throw new Error( 'Cannot require undefined file ' + fileName );
	}

	var result,
	fileContent = scriptFiles[ fileName ];
	if ( typeof fileContent === 'function' ) {
	var moduleParam = { exports: {} };
	fileContent( makeRequireFunction( moduleObj, fileName ), moduleParam, moduleParam.exports );
	result = moduleParam.exports;
	} else {
	// fileContent is raw data (such as a JSON object), just pass it through
	result = fileContent;
	}
	moduleObj.packageExports[ fileName ] = result;
	return result;
	};
	}

	/**
	* Load and execute a script.
	*
	* @private
	* @param {string} src URL to script, will be used as the src attribute in the script tag
	* @param {Function} [callback] Callback to run after request resolution
	* @param {string[]} [modules] List of modules being requested, for state to be marked as error
	* in case the script fails to load
	* @return {HTMLElement}
	*/
	function addScript( src, callback, modules ) {
	// Use a <script> element rather than XHR. Using XHR changes the request
	// headers (potentially missing a cache hit), and reduces caching in general
	// since browsers cache XHR much less (if at all). And XHR means we retrieve
	// text, so we'd need to eval, which then messes up line numbers.
	// The drawback is that <script> does not offer progress events, feedback is
	// only given after downloading, parsing, and execution have completed.
	var script = document.createElement( 'script' );
	script.src = src;
	function onComplete() {
	if ( script.parentNode ) {
	script.parentNode.removeChild( script );
	}
	if ( callback ) {
	callback();
	callback = null;
	}
	}
	script.onload = onComplete;
	script.onerror = function () {
	onComplete();
	if ( modules ) {
	for ( var i = 0; i < modules.length; i++ ) {
	setAndPropagate( modules[ i ], 'error' );
	}
	}
	};
	document.head.appendChild( script );
	return script;
	}

	/**
	* Queue the loading and execution of a script for a particular module.
	*
	* This does for legacy debug mode what runScript() does for production.
	*
	* @private
	* @param {string} src URL of the script
	* @param {string} moduleName Name of currently executing module
	* @param {Function} callback Callback to run after addScript() resolution
	*/
	function queueModuleScript( src, moduleName, callback ) {
	pendingRequests.push( function () {
	// Keep in sync with execute()/runScript().
	if ( moduleName !== 'jquery' ) {
	window.require = mw.loader.require;
	window.module = registry[ moduleName ].module;
	}
	addScript( src, function () {
	// 'module.exports' should not persist after the file is executed to
	// avoid leakage to unrelated code. 'require' should be kept, however,
	// as asynchronous access to 'require' is allowed and expected. (T144879)
	delete window.module;
	callback();
	// Start the next one (if any)
	if ( pendingRequests[ 0 ] ) {
	pendingRequests.shift()();
	} else {
	handlingPendingRequests = false;
	}
	} );
	} );
	if ( !handlingPendingRequests && pendingRequests[ 0 ] ) {
	handlingPendingRequests = true;
	pendingRequests.shift()();
	}
	}

	/**
	* Utility function for execute()
	*
	* @ignore
	* @param {string} url URL
	* @param {string} [media] Media attribute
	* @param {Node\|null} [nextNode]
	* @return {HTMLElement}
	*/
	function addLink( url, media, nextNode ) {
	var el = document.createElement( 'link' );

	el.rel = 'stylesheet';
	if ( media ) {
	el.media = media;
	}
	// If you end up here from an IE exception "SCRIPT: Invalid property value.",
	// see #addEmbeddedCSS, T33676, T43331, and T49277 for details.
	el.href = url;

	addToHead( el, nextNode );
	return el;
	}

	/**
	* Evaluate in the global scope.
	*
	* This is used by MediaWiki user scripts, where it is (for example)
	* important that `var` makes a global variable.
	*
	* @private
	* @param {string} code JavaScript code
	*/
	function globalEval( code ) {
	var script = document.createElement( 'script' );
	script.text = code;
	document.head.appendChild( script );
	script.parentNode.removeChild( script );
	}

	/**
	* Evaluate JS code using indirect eval().
	*
	* This is used by mw.loader.store. It is important that we protect the
	* integrity of mw.loader's private variables (from accidental clashes
	* or re-assignment), which means we can't use regular `eval()`.
	*
	* Optimization: This exists separately from globalEval(), because that
	* involves slow DOM overhead.
	*
	* @private
	* @param {string} code JavaScript code
	*/
	function indirectEval( code ) {
	// See http://perfectionkills.com/global-eval-what-are-the-options/
	// for an explanation of this syntax.
	// eslint-disable-next-line no-eval
	( 1, eval )( code );
	}

	/**
	* Add one or more modules to the module load queue.
	*
	* See also #work().
	*
	* @private
	* @param {string[]} dependencies Array of module names in the registry
	* @param {Function} [ready] Callback to execute when all dependencies are ready
	* @param {Function} [error] Callback to execute when any dependency fails
	*/
	function enqueue( dependencies, ready, error ) {
	if ( allReady( dependencies ) ) {
	// Run ready immediately
	if ( ready ) {
	ready();
	}
	return;
	}

	var failed = anyFailed( dependencies );
	if ( failed !== false ) {
	if ( error ) {
	// Execute error immediately if any dependencies have errors
	error(
	new Error( 'Dependency ' + failed + ' failed to load' ),
	dependencies
	);
	}
	return;
	}

	// Not all dependencies are ready, add to the load queue...

	// Add ready and error callbacks if they were given
	if ( ready \|\| error ) {
	jobs.push( {
	// Narrow down the list to modules that are worth waiting for
	dependencies: dependencies.filter( function ( module ) {
	var state = registry[ module ].state;
	return state === 'registered' \|\| state === 'loaded' \|\| state === 'loading' \|\| state === 'executing';
	} ),
	ready: ready,
	error: error
	} );
	}

	dependencies.forEach( function ( module ) {
	// Only queue modules that are still in the initial 'registered' state
	// (e.g. not ones already loading or loaded etc.).
	if ( registry[ module ].state === 'registered' && queue.indexOf( module ) === -1 ) {
	queue.push( module );
	}
	} );

	mw.loader.work();
	}

	/**
	* Executes a loaded module, making it ready to use
	*
	* @private
	* @param {string} module Module name to execute
	*/
	function execute( module ) {
	if ( registry[ module ].state !== 'loaded' ) {
	throw new Error( 'Module in state "' + registry[ module ].state + '" may not execute: ' + module );
	}

	registry[ module ].state = 'executing';
	$CODE.profileExecuteStart();

	var runScript = function () {
	$CODE.profileScriptStart();
	var script = registry[ module ].script;
	var markModuleReady = function () {
	$CODE.profileScriptEnd();
	setAndPropagate( module, 'ready' );
	};
	var nestedAddScript = function ( arr, offset ) {
	// Recursively call queueModuleScript() in its own callback
	// for each element of arr.
	if ( offset >= arr.length ) {
	// We're at the end of the array
	markModuleReady();
	return;
	}

	queueModuleScript( arr[ offset ], module, function () {
	nestedAddScript( arr, offset + 1 );
	} );
	};

	try {
	if ( Array.isArray( script ) ) {
	nestedAddScript( script, 0 );
	} else if ( typeof script === 'function' ) {
	// Keep in sync with queueModuleScript() for debug mode
	if ( module === 'jquery' ) {
	// This is a special case for when 'jquery' itself is being loaded.
	// - The standard jquery.js distribution does not set `window.jQuery`
	// in CommonJS-compatible environments (Node.js, AMD, RequireJS, etc.).
	// - MediaWiki's 'jquery' module also bundles jquery.migrate.js, which
	// in a CommonJS-compatible environment, will use require('jquery'),
	// but that can't work when we're still inside that module.
	script();
	} else {
	// Pass jQuery twice so that the signature of the closure which wraps
	// the script can bind both '$' and 'jQuery'.
	script( window.$, window.$, mw.loader.require, registry[ module ].module );
	}
	markModuleReady();
	} else if ( typeof script === 'object' && script !== null ) {
	var mainScript = script.files[ script.main ];
	if ( typeof mainScript !== 'function' ) {
	throw new Error( 'Main file in module ' + module + ' must be a function' );
	}
	// jQuery parameters are not passed for multi-file modules
	mainScript(
	makeRequireFunction( registry[ module ], script.main ),
	registry[ module ].module,
	registry[ module ].module.exports
	);
	markModuleReady();
	} else if ( typeof script === 'string' ) {
	// Site and user modules are legacy scripts that run in the global scope.
	// This is transported as a string instead of a function to avoid needing
	// to use string manipulation to undo the function wrapper.
	globalEval( script );
	markModuleReady();

	} else {
	// Module without script
	markModuleReady();
	}
	} catch ( e ) {
	// Use mw.trackError instead of mw.log because these errors are common in production mode
	// (e.g. undefined variable), and mw.log is only enabled in debug mode.
	setAndPropagate( module, 'error' );
	$CODE.profileScriptEnd();
	mw.trackError( {
	exception: e,
	module: module,
	source: 'module-execute'
	} );
	}
	};

	// Emit deprecation warnings
	if ( registry[ module ].deprecationWarning ) {
	mw.log.warn( registry[ module ].deprecationWarning );
	}

	// Add localizations to message system
	if ( registry[ module ].messages ) {
	mw.messages.set( registry[ module ].messages );
	}

	// Initialise templates
	if ( registry[ module ].templates ) {
	mw.templates.set( module, registry[ module ].templates );
	}

	// Adding of stylesheets is asynchronous via addEmbeddedCSS().
	// The below function uses a counting semaphore to make sure we don't call
	// runScript() until after this module's stylesheets have been inserted
	// into the DOM.
	var cssPending = 0;
	var cssHandle = function () {
	// Increase semaphore, when creating a callback for addEmbeddedCSS.
	cssPending++;
	return function () {
	// Decrease semaphore, when said callback is invoked.
	cssPending--;
	if ( cssPending === 0 ) {
	// Paranoia:
	// This callback is exposed to addEmbeddedCSS, which is outside the execute()
	// function and is not concerned with state-machine integrity. In turn,
	// addEmbeddedCSS() actually exposes stuff further via requestAnimationFrame.
	// If increment and decrement callbacks happen in the wrong order, or start
	// again afterwards, then this branch could be reached multiple times.
	// To protect the integrity of the state-machine, prevent that from happening
	// by making runScript() cannot be called more than once. We store a private
	// reference when we first reach this branch, then deference the original, and
	// call our reference to it.
	var runScriptCopy = runScript;
	runScript = undefined;
	runScriptCopy();
	}
	};
	};

	// Process styles (see also mw.loader.impl)
	// * { "css": [css, ..] }
	// * { "url": { <media>: [url, ..] } }
	var style = registry[ module ].style;
	if ( style ) {
	// Array of CSS strings under key 'css'
	// { "css": [css, ..] }
	if ( 'css' in style ) {
	for ( var i = 0; i < style.css.length; i++ ) {
	addEmbeddedCSS( style.css[ i ], cssHandle() );
	}
	}

	// Plain object with array of urls under a media-type key
	// { "url": { <media>: [url, ..] } }
	if ( 'url' in style ) {
	for ( var media in style.url ) {
	var urls = style.url[ media ];
	for ( var j = 0; j < urls.length; j++ ) {
	addLink( urls[ j ], media, marker );
	}
	}
	}
	}

	// End profiling of execute()-self before we call runScript(),
	// which we want to measure separately without overlap.
	$CODE.profileExecuteEnd();

	if ( module === 'user' ) {
	// Implicit dependency on the site module. Not a real dependency because it should
	// run after 'site' regardless of whether it succeeds or fails.
	// Note: This is a simplified version of mw.loader.using(), inlined here because
	// mw.loader.using() is part of mediawiki.base (depends on jQuery; T192623).
	var siteDeps;
	var siteDepErr;
	try {
	siteDeps = resolve( [ 'site' ] );
	} catch ( e ) {
	siteDepErr = e;
	runScript();
	}
	if ( !siteDepErr ) {
	enqueue( siteDeps, runScript, runScript );
	}
	} else if ( cssPending === 0 ) {
	// Regular module without styles
	runScript();
	}
	// else: runScript will get called via cssHandle()
	}

	function sortQuery( o ) {
	var sorted = {};
	var list = [];

	for ( var key in o ) {
	list.push( key );
	}
	list.sort();
	for ( var i = 0; i < list.length; i++ ) {
	sorted[ list[ i ] ] = o[ list[ i ] ];
	}
	return sorted;
	}

	/**
	* Converts a module map of the form `{ foo: [ 'bar', 'baz' ], bar: [ 'baz, 'quux' ] }`
	* to a query string of the form `foo.bar,baz\|bar.baz,quux`.
	*
	* See `ResourceLoader::makePackedModulesString()` in PHP, of which this is a port.
	* On the server, unpacking is done by `ResourceLoader::expandModuleNames()`.
	*
	* Note: This is only half of the logic, the other half has to be in #batchRequest(),
	* because its implementation needs to keep track of potential string size in order
	* to decide when to split the requests due to url size.
	*
	* @typedef {Object} ModuleString
	* @property {string} str Module query string
	* @property {Array} list List of module names in matching order
	*
	* @private
	* @param {Object} moduleMap Module map
	* @return {ModuleString}
	*/
	function buildModulesString( moduleMap ) {
	var str = [];
	var list = [];
	var p;

	function restore( suffix ) {
	return p + suffix;
	}

	for ( var prefix in moduleMap ) {
	p = prefix === '' ? '' : prefix + '.';
	str.push( p + moduleMap[ prefix ].join( ',' ) );
	list.push.apply( list, moduleMap[ prefix ].map( restore ) );
	}
	return {
	str: str.join( '\|' ),
	list: list
	};
	}

	/**
	* @private
	* @param {Object} params Map of parameter names to values
	* @return {string}
	*/
	function makeQueryString( params ) {
	// Optimisation: This is a fairly hot code path with batchRequest() loops.
	// Avoid overhead from Object.keys and Array.forEach.
	// String concatenation is faster than array pushing and joining, see
	// https://phabricator.wikimedia.org/P19931
	var str = '';
	for ( var key in params ) {
	// Parameters are separated by &, added before all parameters other than
	// the first
	str += ( str ? '&' : '' ) + encodeURIComponent( key ) + '=' +
	encodeURIComponent( params[ key ] );
	}
	return str;
	}

	/**
	* Create network requests for a batch of modules.
	*
	* This is an internal method for #work(). This must not be called directly
	* unless the modules are already registered, and no request is in progress,
	* and the module state has already been set to `loading`.
	*
	* @private
	* @param {string[]} batch
	*/
	function batchRequest( batch ) {
	if ( !batch.length ) {
	return;
	}

	var sourceLoadScript, currReqBase, moduleMap;

	/**
	* Start the currently drafted request to the server.
	*
	* @ignore
	*/
	function doRequest() {
	// Optimisation: Inherit (Object.create), not copy ($.extend)
	var query = Object.create( currReqBase ),
	packed = buildModulesString( moduleMap );
	query.modules = packed.str;
	// The packing logic can change the effective order, even if the input was
	// sorted. As such, the call to getCombinedVersion() must use this
	// effective order to ensure that the combined version will match the hash
	// expected by the server based on combining versions from the module
	// query string in-order. (T188076)
	query.version = getCombinedVersion( packed.list );
	query = sortQuery( query );
	addScript( sourceLoadScript + '?' + makeQueryString( query ), null, packed.list );
	}

	// Always order modules alphabetically to help reduce cache
	// misses for otherwise identical content.
	batch.sort();

	// Query parameters common to all requests
	var reqBase = $VARS.reqBase;

	// Split module list by source and by group.
	var splits = Object.create( null );
	for ( var b = 0; b < batch.length; b++ ) {
	var bSource = registry[ batch[ b ] ].source;
	var bGroup = registry[ batch[ b ] ].group;
	if ( !splits[ bSource ] ) {
	splits[ bSource ] = Object.create( null );
	}
	if ( !splits[ bSource ][ bGroup ] ) {
	splits[ bSource ][ bGroup ] = [];
	}
	splits[ bSource ][ bGroup ].push( batch[ b ] );
	}

	for ( var source in splits ) {
	sourceLoadScript = sources[ source ];

	for ( var group in splits[ source ] ) {

	// Cache access to currently selected list of
	// modules for this group from this source.
	var modules = splits[ source ][ group ];

	// Query parameters common to requests for this module group
	// Optimisation: Inherit (Object.create), not copy ($.extend)
	currReqBase = Object.create( reqBase );
	// User modules require a user name in the query string.
	if ( group === $VARS.groupUser && mw.config.get( 'wgUserName' ) !== null ) {
	currReqBase.user = mw.config.get( 'wgUserName' );
	}

	// In addition to currReqBase, doRequest() will also add 'modules' and 'version'.
	// > '&modules='.length === 9
	// > '&version=12345'.length === 14
	// > 9 + 14 = 23
	var currReqBaseLength = makeQueryString( currReqBase ).length + 23;

	// We may need to split up the request to honor the query string length limit,
	// so build it piece by piece. `length` does not include the characters from
	// the request base, see below
	var length = 0;
	moduleMap = Object.create( null ); // { prefix: [ suffixes ] }

	for ( var i = 0; i < modules.length; i++ ) {
	// Determine how many bytes this module would add to the query string
	var lastDotIndex = modules[ i ].lastIndexOf( '.' ),
	prefix = modules[ i ].slice( 0, Math.max( 0, lastDotIndex ) ),
	suffix = modules[ i ].slice( lastDotIndex + 1 ),
	bytesAdded = moduleMap[ prefix ] ?
	suffix.length + 3 : // '%2C'.length == 3
	modules[ i ].length + 3; // '%7C'.length == 3

	// If the url would become too long, create a new one, but don't create empty requests.
	// The value of `length` only reflects the request-specific bytes relating to the
	// accumulated entries in moduleMap so far. It does not include the base length,
	// which we account for separately with `currReqBaseLength` so that length is 0
	// when moduleMap is empty.
	if ( length && length + currReqBaseLength + bytesAdded > mw.loader.maxQueryLength ) {
	// Dispatch what we've got...
	doRequest();
	// .. and start preparing a new request.
	length = 0;
	moduleMap = Object.create( null );
	}
	if ( !moduleMap[ prefix ] ) {
	moduleMap[ prefix ] = [];
	}
	length += bytesAdded;
	moduleMap[ prefix ].push( suffix );
	}
	// Optimization: Skip `length` check.
	// moduleMap will contain at least one module here. The loop above leaves the last module
	// undispatched (and maybe some before it), so for moduleMap to be empty here, there must
	// have been no modules to iterate in the current group to start with, but we only create
	// a group in `splits` when the first module in the group is seen, so there are always
	// modules in the group when this code is reached.
	doRequest();
	}
	}
	}

	/**
	* @private
	* @param {string[]} implementations Array containing pieces of JavaScript code in the
	* form of calls to mw.loader#impl().
	* @param {Function} cb Callback in case of failure
	* @param {Error} cb.err
	* @param {number} [offset] Integer offset into implementations to start at
	*/
	function asyncEval( implementations, cb, offset ) {
	if ( !implementations.length ) {
	return;
	}
	offset = offset \|\| 0;
	mw.requestIdleCallback( function ( deadline ) {
	asyncEvalTask( deadline, implementations, cb, offset );
	} );
	}

	/**
	* Idle callback for asyncEval
	*
	* @private
	* @param {IdleDeadline} deadline
	* @param {string[]} implementations
	* @param {Function} cb
	* @param {Error} cb.err
	* @param {number} offset
	*/
	function asyncEvalTask( deadline, implementations, cb, offset ) {
	for ( var i = offset; i < implementations.length; i++ ) {
	if ( deadline.timeRemaining() <= 0 ) {
	asyncEval( implementations, cb, i );
	return;
	}
	try {
	indirectEval( implementations[ i ] );
	} catch ( err ) {
	cb( err );
	}
	}
	}

	/**
	* Make a versioned key for a specific module.
	*
	* @private
	* @param {string} module Module name
	* @return {string\|null} Module key in format '`[name]@[version]`',
	* or null if the module does not exist
	*/
	function getModuleKey( module ) {
	return module in registry ? ( module + '@' + registry[ module ].version ) : null;
	}

	/**
	* @private
	* @param {string} key Module name or '`[name]@[version]`'
	* @return {Object}
	*/
	function splitModuleKey( key ) {
	// Module names may contain '@' but version strings may not, so the last '@' is the delimiter
	var index = key.lastIndexOf( '@' );
	// If the key doesn't contain '@' or starts with it, the whole thing is the module name
	if ( index === -1 \|\| index === 0 ) {
	return {
	name: key,
	version: ''
	};
	}
	return {
	name: key.slice( 0, index ),
	version: key.slice( index + 1 )
	};
	}

	/**
	* @private
	* @param {string} module
	* @param {string} [version]
	* @param {string[]} [dependencies]
	* @param {string} [group]
	* @param {string} [source]
	* @param {string} [skip]
	*/
	function registerOne( module, version, dependencies, group, source, skip ) {
	if ( module in registry ) {
	throw new Error( 'module already registered: ' + module );
	}

	registry[ module ] = {
	// Exposed to execute() for mw.loader.impl() closures.
	// Import happens via require().
	module: {
	exports: {}
	},
	// module.export objects for each package file inside this module
	packageExports: {},
	version: version \|\| '',
	dependencies: dependencies \|\| [],
	group: typeof group === 'undefined' ? null : group,
	source: typeof source === 'string' ? source : 'local',
	state: 'registered',
	skip: typeof skip === 'string' ? skip : null
	};
	}

	/* Public Members */

	mw.loader = {
	/**
	* The module registry is exposed as an aid for debugging and inspecting page
	* state; it is not a public interface for modifying the registry.
	*
	* @see #registry
	* @property {Object}
	* @private
	*/
	moduleRegistry: registry,

	/**
	* Exposed for testing and debugging only.
	*
	* @see #batchRequest
	* @property {number}
	* @private
	*/
	maxQueryLength: $VARS.maxQueryLength,

	addStyleTag: newStyleTag,

	// Exposed for internal use only. Documented as @private.
	addScriptTag: addScript,
	// Exposed for internal use only. Documented as @private.
	addLinkTag: addLink,

	// Exposed for internal use only. Documented as @private.
	enqueue: enqueue,

	// Exposed for internal use only. Documented as @private.
	resolve: resolve,

	/**
	* Start loading of all queued module dependencies.
	*
	* @private
	*/
	work: function () {
	store.init();

	var q = queue.length,
	storedImplementations = [],
	storedNames = [],
	requestNames = [],
	batch = new Set();

	// Iterate the list of requested modules, and do one of three things:
	// - 1) Nothing (if already loaded or being loaded).
	// - 2) Eval the cached implementation from the module store.
	// - 3) Request from network.
	while ( q-- ) {
	var module = queue[ q ];
	// Only consider modules which are the initial 'registered' state,
	// and ignore duplicates
	if ( mw.loader.getState( module ) === 'registered' &&
	!batch.has( module )
	) {
	// Progress the state machine
	registry[ module ].state = 'loading';
	batch.add( module );

	var implementation = store.get( module );
	if ( implementation ) {
	// Module store enabled and contains this module/version
	storedImplementations.push( implementation );
	storedNames.push( module );
	} else {
	// Module store disabled or doesn't have this module/version
	requestNames.push( module );
	}
	}
	}

	// Now that the queue has been processed into a batch, clear the queue.
	// This MUST happen before we initiate any eval or network request. Otherwise,
	// it is possible for a cached script to instantly trigger the same work queue
	// again; all before we've cleared it causing each request to include modules
	// which are already loaded.
	queue = [];

	asyncEval( storedImplementations, function ( err ) {
	// Not good, the cached mw.loader.impl calls failed! This should
	// never happen, barring ResourceLoader bugs, browser bugs and PEBKACs.
	// Depending on how corrupt the string is, it is likely that some
	// modules' impl() succeeded while the ones after the error will
	// never run and leave their modules in the 'loading' state forever.
	store.stats.failed++;

	// Since this is an error not caused by an individual module but by
	// something that infected the implement call itself, don't take any
	// risks and clear everything in this cache.
	store.clear();

	mw.trackError( {
	exception: err,
	source: 'store-eval'
	} );
	// For any failed ones, fallback to requesting from network
	var failed = storedNames.filter( function ( name ) {
	return registry[ name ].state === 'loading';
	} );
	batchRequest( failed );
	} );

	batchRequest( requestNames );
	},

	/**
	* Register a source.
	*
	* The #work() method will use this information to split up requests by source.
	*
	* @example
	* mw.loader.addSource( { mediawikiwiki: 'https://www.mediawiki.org/w/load.php' } );
	*
	* @private
	* @param {Object} ids An object mapping ids to load.php end point urls
	* @throws {Error} If source id is already registered
	*/
	addSource: function ( ids ) {
	for ( var id in ids ) {
	if ( id in sources ) {
	throw new Error( 'source already registered: ' + id );
	}
	sources[ id ] = ids[ id ];
	}
	},

	/**
	* Register a module, letting the system know about it and its properties.
	*
	* The startup module calls this method.
	*
	* When using multiple module registration by passing an array, dependencies that
	* are specified as references to modules within the array will be resolved before
	* the modules are registered.
	*
	* @param {string\|Array} modules Module name or array of arrays, each containing
	* a list of arguments compatible with this method
	* @param {string} [version] Module version hash (falls backs to empty string)
	* @param {string[]} [dependencies] Array of module names on which this module depends.
	* @param {string} [group=null] Group which the module is in
	* @param {string} [source='local'] Name of the source
	* @param {string} [skip=null] Script body of the skip function
	* @private
	*/
	register: function ( modules ) {
	if ( typeof modules !== 'object' ) {
	registerOne.apply( null, arguments );
	return;
	}
	// Need to resolve indexed dependencies:
	// ResourceLoader uses an optimisation to save space which replaces module
	// names in dependency lists with the index of that module within the
	// array of module registration data if it exists. The benefit is a significant
	// reduction in the data size of the startup module. This loop changes
	// those dependency lists back to arrays of strings.
	function resolveIndex( dep ) {
	return typeof dep === 'number' ? modules[ dep ][ 0 ] : dep;
	}

	for ( var i = 0; i < modules.length; i++ ) {
	var deps = modules[ i ][ 2 ];
	if ( deps ) {
	for ( var j = 0; j < deps.length; j++ ) {
	deps[ j ] = resolveIndex( deps[ j ] );
	}
	}
	// Optimisation: Up to 55% faster.
	// Typically register() is called exactly once on a page, and with a batch.
	// See <https://gist.github.com/Krinkle/f06fdb3de62824c6c16f02a0e6ce0e66>
	// Benchmarks taught us that the code for adding an object to `registry`
	// should be in a function that has only one signature and does no arguments
	// manipulation.
	// JS semantics make it hard to optimise recursion to a different
	// signature of itself, hence we moved this out.
	registerOne.apply( null, modules[ i ] );
	}
	},

	/**
	* Implement a module given the components of the module.
	*
	* See #impl for a full description of the parameters.
	*
	* Prior to MW 1.41, this was used internally, but now it is only kept
	* for backwards compatibility.
	*
	* Does not support mw.loader.store caching.
	*
	* @param {string} module
	* @param {Function\|Array\|string\|Object} [script]
	* @param {Object} [style]
	* @param {Object} [messages] List of key/value pairs to be added to mw#messages.
	* @param {Object} [templates] List of key/value pairs to be added to mw#templates.
	* @param {string\|null} [deprecationWarning] Deprecation warning if any
	* @private
	*/
	implement: function ( module, script, style, messages, templates, deprecationWarning ) {
	var split = splitModuleKey( module ),
	name = split.name,
	version = split.version;

	// Automatically register module
	if ( !( name in registry ) ) {
	mw.loader.register( name );
	}
	// Check for duplicate implementation
	if ( registry[ name ].script !== undefined ) {
	throw new Error( 'module already implemented: ' + name );
	}
	registry[ name ].version = version;
	registry[ name ].declarator = null; // not supported
	registry[ name ].script = script;
	registry[ name ].style = style;
	registry[ name ].messages = messages;
	registry[ name ].templates = templates;
	registry[ name ].deprecationWarning = deprecationWarning;
	// The module may already have been marked as erroneous
	if ( registry[ name ].state !== 'error' && registry[ name ].state !== 'missing' ) {
	setAndPropagate( name, 'loaded' );
	}
	},

	/**
	* Implement a module given a function which returns the components of the module
	*
	* @param {Function} declarator
	*
	* The declarator should return an array with the following keys:
	*
	* - 0. {string} module Name of module and current module version. Formatted
	* as '`[name]@[version]`". This version should match the requested version
	* (from #batchRequest and #registry). This avoids race conditions (T117587).
	*
	* - 1. {Function\|Array\|string\|Object} [script] Module code. This can be a function,
	* a list of URLs to load via `<script src>`, a string for `globalEval()`, or an
	* object like {"files": {"foo.js":function, "bar.js": function, ...}, "main": "foo.js"}.
	* If an object is provided, the main file will be executed immediately, and the other
	* files will only be executed if loaded via require(). If a function or string is
	* provided, it will be executed/evaluated immediately. If an array is provided, all
	* URLs in the array will be loaded immediately, and executed as soon as they arrive.
	*
	* - 2. {Object} [style] Should follow one of the following patterns:
	*
	* { "css": [css, ..] }
	* { "url": { (media): [url, ..] } }
	*
	* The reason css strings are not concatenated anymore is T33676. We now check
	* whether it's safe to extend the stylesheet.
	*
	* - 3. {Object} [messages] List of key/value pairs to be added to mw#messages.
	* - 4. {Object} [templates] List of key/value pairs to be added to mw#templates.
	* - 5. {String\|null} [deprecationWarning] Deprecation warning if any
	*
	* The declarator must not use any scope variables, since it will be serialized with
	* Function.prototype.toString() and later restored and executed in the global scope.
	*
	* The elements are all optional except the name.
	* @private
	*/
	impl: function ( declarator ) {
	var data = declarator(),
	module = data[ 0 ],
	script = data[ 1 ] \|\| null,
	style = data[ 2 ] \|\| null,
	messages = data[ 3 ] \|\| null,
	templates = data[ 4 ] \|\| null,
	deprecationWarning = data[ 5 ] \|\| null,
	split = splitModuleKey( module ),
	name = split.name,
	version = split.version;

	// Automatically register module
	if ( !( name in registry ) ) {
	mw.loader.register( name );
	}
	// Check for duplicate implementation
	if ( registry[ name ].script !== undefined ) {
	throw new Error( 'module already implemented: ' + name );
	}
	// Without this reset, if there is a version mismatch between the
	// requested and received module version, then mw.loader.store would
	// cache the response under the requested key. Thus poisoning the cache
	// indefinitely with a stale value. (T117587)
	registry[ name ].version = version;
	// Attach components
	registry[ name ].declarator = declarator;
	registry[ name ].script = script;
	registry[ name ].style = style;
	registry[ name ].messages = messages;
	registry[ name ].templates = templates;
	registry[ name ].deprecationWarning = deprecationWarning;
	// The module may already have been marked as erroneous
	if ( registry[ name ].state !== 'error' && registry[ name ].state !== 'missing' ) {
	setAndPropagate( name, 'loaded' );
	}
	},

	/**
	* Load an external script or one or more modules.
	*
	* This method takes a list of unrelated modules. Use cases:
	*
	* - A web page will be composed of many different widgets. These widgets independently
	* queue their ResourceLoader modules (`OutputPage::addModules()`). If any of them
	* have problems, or are no longer known (e.g. cached HTML), the other modules
	* should still be loaded.
	* - This method is used for preloading, which must not throw. Later code that
	* calls #using() will handle the error.
	*
	* @param {string\|Array} modules Either the name of a module, array of modules,
	* or a URL of an external script or style
	* @param {string} [type='text/javascript'] MIME type to use if calling with a URL of an
	* external script or style; acceptable values are "text/css" and
	* "text/javascript"; if no type is provided, text/javascript is assumed.
	* @throws {Error} If type is invalid
	*/
	load: function ( modules, type ) {

	if ( typeof modules === 'string' && /^(https?:)?\/?\//.test( modules ) ) {
	// Called with a url like so:
	// - "https://example.org/x.js"
	// - "http://example.org/x.js"
	// - "//example.org/x.js"
	// - "/x.js"
	if ( type === 'text/css' ) {
	addLink( modules );
	} else if ( type === 'text/javascript' \|\| type === undefined ) {
	addScript( modules );
	} else {
	// Unknown type
	throw new Error( 'Invalid type ' + type );
	}
	} else {
	// One or more modules
	modules = typeof modules === 'string' ? [ modules ] : modules;
	// Resolve modules into a flat list for internal queuing.
	// This also filters out unknown modules and modules with
	// unknown dependencies, allowing the rest to continue. (T36853)
	// Omit ready and error parameters, we don't have callbacks
	enqueue( resolveStubbornly( modules ) );
	}
	},

	/**
	* Change the state of one or more modules.
	*
	* @param {Object} states Object of module name/state pairs
	* @private
	*/
	state: function ( states ) {
	for ( var module in states ) {
	if ( !( module in registry ) ) {
	mw.loader.register( module );
	}
	setAndPropagate( module, states[ module ] );
	}
	},

	/**
	* Get the state of a module.
	*
	* Possible states for the public API:
	*
	* - `registered`: The module is available for loading but not yet requested.
	* - `loading`, `loaded`, or `executing`: The module is currently being loaded.
	* - `ready`: The module was successfully and fully loaded.
	* - `error`: The module or one its dependencies has failed to load, e.g. due to
	* uncaught error from the module's script files.
	* - `missing`: The module was requested but is not defined according to the server.
	*
	* Internal mw.loader state machine:
	*
	* - `registered`:
	* The module is known to the system but not yet required.
	* Meta data is stored by `register()`.
	* Calls to that method are generated server-side by StartupModule.
	* - `loading`:
	* The module was required through mw.loader (either directly or as dependency of
	* another module). The client will fetch module contents from mw.loader.store
	* or from the server. The contents should later be received by `implement()`.
	* - `loaded`:
	* The module has been received by `implement()`.
	* Once the module has no more dependencies in-flight, the module will be executed,
	* controlled via `setAndPropagate()` and `doPropagation()`.
	* - `executing`:
	* The module is being executed (apply messages and stylesheets, execute scripts)
	* by `execute()`.
	* - `ready`:
	* The module has been successfully executed.
	* - `error`:
	* The module (or one of its dependencies) produced an uncaught error during execution.
	* - `missing`:
	* The module was registered client-side and requested, but the server denied knowledge
	* of the module's existence.
	*
	* @param {string} module Name of module
	* @return {string\|null} The state, or null if the module (or its state) is not
	* in the registry.
	*/
	getState: function ( module ) {
	return module in registry ? registry[ module ].state : null;
	},

	/**
	* Get the exported value of a module.
	*
	* This static method is publicly exposed for debugging purposes
	* only and must not be used in production code. In production code,
	* please use the dynamically provided `require()` function instead.
	*
	* In case of lazy-loaded modules via mw.loader#using(), the returned
	* Promise provides the function, see #using() for examples.
	*
	* @private
	* @since 1.27
	* @param {string} moduleName Module name
	* @return {any} Exported value
	*/
	require: function ( moduleName ) {
	var path;
	if ( window.QUnit ) {
	// Comply with Node specification
	// https://nodejs.org/docs/v20.1.0/api/modules.html#all-together
	//
	// > Interpret X as a combination of NAME and SUBPATH, where the NAME
	// > may have a "@scope/" prefix and the subpath begins with a slash (`/`).
	//
	// Regex inspired by Node [1], but simplified to suite our purposes
	// and split in two in order to keep the Regex Star Height under 2,
	// as per ESLint security/detect-unsafe-regex.
	//
	// These patterns match "@scope/module/dir/file.js" and "module/dir/file.js"
	// respectively. They must not match "module.name" or "@scope/module.name".
	//
	// [1] https://github.com/nodejs/node/blob/v20.1.0/lib/internal/modules/cjs/loader.js#L554-L560
	var paths = moduleName.startsWith( '@' ) ?
	/^(@[^/]+\/[^/]+)\/(.*)$/.exec( moduleName ) :
	// eslint-disable-next-line no-mixed-spaces-and-tabs
	/^([^/]+)\/(.*)$/.exec( moduleName );
	if ( paths ) {
	moduleName = paths[ 1 ];
	path = paths[ 2 ];
	}
	}

	// Only ready modules can be required
	if ( mw.loader.getState( moduleName ) !== 'ready' ) {
	// Module may've forgotten to declare a dependency
	throw new Error( 'Module "' + moduleName + '" is not loaded' );
	}

	return path ?
	makeRequireFunction( registry[ moduleName ], '' )( './' + path ) :
	registry[ moduleName ].module.exports;
	}
	};

	var hasPendingFlush = false,
	hasPendingWrites = false;

	/**
	* Actually update the store
	*
	* @see #requestUpdate
	* @private
	*/
	function flushWrites() {
	// Process queued module names, serialise their contents to the in-memory store.
	while ( store.queue.length ) {
	store.set( store.queue.shift() );
	}

	// Optimization: Don't reserialize the entire store and rewrite localStorage,
	// if no module was added or changed.
	if ( hasPendingWrites ) {
	// Remove anything from the in-memory store that came from previous page
	// loads that no longer corresponds with current module names and versions.
	store.prune();

	try {
	// Replacing the content of the module store might fail if the new
	// contents would exceed the browser's localStorage size limit. To
	// avoid clogging the browser with stale data, always remove the old
	// value before attempting to store a new one.
	localStorage.removeItem( store.key );
	localStorage.setItem( store.key, JSON.stringify( {
	items: store.items,
	vary: store.vary,
	// Store with 1e7 ms accuracy (1e4 seconds, or ~ 2.7 hours),
	// which is enough for the purpose of expiring after ~ 30 days.
	asOf: Math.ceil( Date.now() / 1e7 )
	} ) );
	} catch ( e ) {
	mw.trackError( {
	exception: e,
	source: 'store-localstorage-update'
	} );
	}
	}

	// Let the next call to requestUpdate() create a new timer.
	hasPendingFlush = hasPendingWrites = false;
	}

	// We use a local variable `store` so that its easier to access, but also need to set
	// this in mw.loader so its exported - combine the two

	/**
	* On browsers that implement the localStorage API, the module store serves as a
	* smart complement to the browser cache. Unlike the browser cache, the module store
	* can slice a concatenated response from ResourceLoader into its constituent
	* modules and cache each of them separately, using each module's versioning scheme
	* to determine when the cache should be invalidated.
	*
	* @private
	* @singleton
	* @class mw.loader.store
	* @ignore
	*/
	mw.loader.store = store = {
	// Whether the store is in use on this page.
	enabled: null,

	// The contents of the store, mapping '[name]@[version]' keys
	// to module implementations.
	items: {},

	// Names of modules to be stored during the next update.
	// See add() and update().
	queue: [],

	// Cache hit stats
	stats: { hits: 0, misses: 0, expired: 0, failed: 0 },

	/**
	* The localStorage key for the entire module store. The key references
	* $wgDBname to prevent clashes between wikis which share a common host.
	*
	* @property {string}
	*/
	key: $VARS.storeKey,

	/**
	* A string containing various factors by which the module cache should vary.
	*
	* Defined by ResourceLoader\StartupModule::getStoreVary() in PHP.
	*
	* @property {string}
	*/
	vary: $VARS.storeVary,

	/**
	* Initialize the store.
	*
	* Retrieves store from localStorage and (if successfully retrieved) decoding
	* the stored JSON value to a plain object.
	*/
	init: function () {
	// Init only once per page
	if ( this.enabled === null ) {
	this.enabled = false;
	if ( $VARS.storeEnabled ) {
	this.load();
	} else {
	// Clear any previous store to free up space. (T66721)
	this.clear();
	}

	}
	},

	/**
	* Internal helper for init(). Separated for ease of testing.
	*/
	load: function () {
	// These are the scenarios to think about:
	//
	// 1. localStorage is disallowed by the browser.
	// This means `localStorage.getItem` throws.
	// The store stays disabled.
	//
	// 2. localStorage did not contain our store key.
	// This usually means the browser has a cold cache for this site,
	// and thus localStorage.getItem returns null.
	// The store will be enabled, and `items` starts fresh.
	//
	// 3. localStorage contains parseable data, but it's not usable.
	// This means the data is too old, or is not valid for mw.loader.store.vary
	// (e.g. user switched skin or language).
	// The store will be enabled, and `items` starts fresh.
	//
	// 4. localStorage contains invalid JSON data.
	// This means the data was corrupted, and `JSON.parse` throws.
	// The store will be enabled, and `items` starts fresh.
	//
	// 5. localStorage contains valid and usable JSON.
	// This means we have a warm cache from a previous visit.
	// The store will be enabled, and `items` starts with the stored data.

	try {
	var raw = localStorage.getItem( this.key );

	// If we make it here, localStorage is enabled and available.
	// The rest of the function may fail, but that only affects what we load from
	// the cache. We'll still enable the store to allow storing new modules.
	this.enabled = true;

	// If getItem returns null, JSON.parse() will cast to string and re-parse, still null.
	var data = JSON.parse( raw );
	if ( data &&
	data.vary === this.vary &&
	data.items &&
	// Only use if it's been less than 30 days since the data was written
	// 30 days = 2,592,000 s = 2,592,000,000 ms = ± 259e7 ms
	Date.now() < ( data.asOf * 1e7 ) + 259e7
	) {
	// The data is not corrupt, matches our vary context, and has not expired.
	this.items = data.items;
	}
	} catch ( e ) {
	// Ignore error from localStorage or JSON.parse.
	// Don't print any warning (T195647).
	}
	},

	/**
	* Retrieve a module from the store and update cache hit stats.
	*
	* @param {string} module Module name
	* @return {string\|boolean} Module implementation or false if unavailable
	*/
	get: function ( module ) {
	if ( this.enabled ) {
	var key = getModuleKey( module );
	if ( key in this.items ) {
	this.stats.hits++;
	return this.items[ key ];
	}

	this.stats.misses++;
	}

	return false;
	},

	/**
	* Queue the name of a module that the next update should consider storing.
	*
	* @since 1.32
	* @param {string} module Module name
	*/
	add: function ( module ) {
	if ( this.enabled ) {
	this.queue.push( module );
	this.requestUpdate();
	}
	},

	/**
	* Add the contents of the named module to the in-memory store.
	*
	* This method does not guarantee that the module will be stored.
	* Inspection of the module's meta data and size will ultimately decide that.
	*
	* This method is considered internal to mw.loader.store and must only
	* be called if the store is enabled.
	*
	* @private
	* @param {string} module Module name
	*/
	set: function ( module ) {
	var descriptor = registry[ module ],
	key = getModuleKey( module );

	if (
	// Already stored a copy of this exact version
	key in this.items \|\|
	// Module failed to load
	!descriptor \|\|
	descriptor.state !== 'ready' \|\|
	// Unversioned, private, or site-/user-specific
	!descriptor.version \|\|
	descriptor.group === $VARS.groupPrivate \|\|
	descriptor.group === $VARS.groupUser \|\|
	// Legacy descriptor, registered with mw.loader.implement
	!descriptor.declarator
	) {
	// Decline to store
	return;
	}

	var script = String( descriptor.declarator );
	// Modules whose serialised form exceeds 100 kB won't be stored (T66721).
	if ( script.length > 1e5 ) {
	return;
	}

	var srcParts = [
	'mw.loader.impl(',
	script,
	');\n'
	];
	if ( $VARS.sourceMapLinks ) {
	srcParts.push( '// Saved in localStorage at ', ( new Date() ).toISOString(), '\n' );
	var sourceLoadScript = sources[ descriptor.source ];
	var query = Object.create( $VARS.reqBase );
	query.modules = module;
	query.version = getCombinedVersion( [ module ] );
	query = sortQuery( query );
	srcParts.push(
	'//# sourceURL=',
	// Use absolute URL so that Firefox console stack trace links will work
	( new URL( sourceLoadScript, location ) ).href,
	'?',
	makeQueryString( query ),
	'\n'
	);

	query.sourcemap = '1';
	query = sortQuery( query );
	srcParts.push(
	'//# sourceMappingURL=',
	sourceLoadScript,
	'?',
	makeQueryString( query )
	);
	}
	this.items[ key ] = srcParts.join( '' );
	hasPendingWrites = true;
	},

	/**
	* Iterate through the module store, removing any item that does not correspond
	* (in name and version) to an item in the module registry.
	*/
	prune: function () {
	for ( var key in this.items ) {
	// key is in the form [name]@[version], slice to get just the name
	// to provide to getModuleKey, which will return a key in the same
	// form but with the latest version
	if ( getModuleKey( splitModuleKey( key ).name ) !== key ) {
	this.stats.expired++;
	delete this.items[ key ];
	}
	}
	},

	/**
	* Clear the entire module store right now.
	*/
	clear: function () {
	this.items = {};
	try {
	localStorage.removeItem( this.key );
	} catch ( e ) {}
	},

	/**
	* Request a sync of the in-memory store back to persisted localStorage.
	*
	* This function debounces updates. The debouncing logic should account
	* for the following factors:
	*
	* - Writing to localStorage is an expensive operation that must not happen
	* during the critical path of initialising and executing module code.
	* Instead, it should happen at a later time after modules have been given
	* time and priority to do their thing first.
	*
	* - This method is called from mw.loader.store.add(), which will be called
	* hundreds of times on a typical page, including within the same call-stack
	* and eventloop-tick. This is because responses from load.php happen in
	* batches. As such, we want to allow all modules from the same load.php
	* response to be written to disk with a single flush, not many.
	*
	* - Repeatedly deleting and creating timers is non-trivial.
	*
	* - localStorage is shared by all pages from the same origin, if multiple
	* pages are loaded with different module sets, the possibility exists that
	* modules saved by one page will be clobbered by another. The impact of
	* this is minor, it merely causes a less efficient cache use, and the
	* problem would be corrected by subsequent page views.
	*
	* This method is considered internal to mw.loader.store and must only
	* be called if the store is enabled.
	*
	* @private
	* @method
	*/
	requestUpdate: function () {
	// On the first call to requestUpdate(), create a timer that
	// waits at least two seconds, then calls onTimeout.
	// The main purpose is to allow the current batch of load.php
	// responses to complete before we do anything. This batch can
	// trigger many hundreds of calls to requestUpdate().
	if ( !hasPendingFlush ) {
	hasPendingFlush = setTimeout(
	// Defer the actual write via requestIdleCallback
	function () {
	mw.requestIdleCallback( flushWrites );
	},
	2000
	);
	}
	}
	};
	}() );

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