mw.loader: Minor clean up and optimisations

* mw.loader.state: Simplify code by removing redundant branch that could set
  the value to what it already was. Also remove the condition for it since
  re-setting it should never happen in practice.
  If it does happen, it's a harmless no-op.

* mw.loader.store.set: Document use cases for descriptor being partial.
  On a most page views, this branch runs for 'site.styles', 'json', 'user',
  'dom-level2-shim', 'mediawiki.hidpi', 'user.options', and 'user.tokens'.
  Aside from group=user modules, the others are skipped or style modules.

* register: Make faster and reduce GC overhead
  (MacBookPro, Chrome canary 52, Vagrant, 566 registered modules)
  Measured using Timeline (JS Profile) and Profile (Allocation Profile).

  - Use typeof instead of isFunction().
  - In resolveIndexedDependencies:
    - Use a for-loop instead of $.each(). This uncovered a JSHint warning for
      making $.map() functions in a loop. Move the function out and re-use it.
    - Use a for-loop instead of $.map().
  - Don't create an empty dependencies array in the registry only to
    dereference it in the next statement.

  Time for register() down from 5-10ms to 3-4ms.
  Memory for register() down
   from 153KB (88% in register, 12% in resolveIndexedDependencies/each/map)
   to 120KB (100% in register, no mention of resolveIndexedDependencies)
  GC down from 350KB to 240KB.

* Remove use of isFunction(). We're not interested in its edge cases of
  native functions in old IE and regex false-positive in Android 2.3.
  For plain user-specified functions, typeof will return 'function'
  in all supported browsers.

Change-Id: I43fc7c7f54d0c279b659d6fddd21673de48f4bc2

diff --git a/resources/src/mediawiki/mediawiki.js b/resources/src/mediawiki/mediawiki.js
index 491564a..af37162 100644 (file)
--- a/resources/src/mediawiki/mediawiki.js
+++ b/resources/src/mediawiki/mediawiki.js
@@ -1068,11 +1068,11 @@
                                                j -= 1;
                                                try {
                                                        if ( hasErrors ) {
-                                                               if ( $.isFunction( job.error ) ) {
+                                                               if ( typeof job.error === 'function' ) {
                                                                        job.error( new Error( 'Module ' + module + ' has failed dependencies' ), [ module ] );
                                                                }
                                                        } else {
-                                                               if ( $.isFunction( job.ready ) ) {
+                                                               if ( typeof job.ready === 'function' ) {
                                                                        job.ready();
                                                                }
                                                        }
@@ -1131,7 +1131,7 @@
                                }
 
                                // Resolves dynamic loader function and replaces it with its own results
-                               if ( $.isFunction( registry[ module ].dependencies ) ) {
+                               if ( typeof registry[ module ].dependencies === 'function' ) {
                                        registry[ module ].dependencies = registry[ module ].dependencies();
                                        // Ensures the module's dependencies are always in an array
                                        if ( typeof registry[ module ].dependencies !== 'object' ) {
@@ -1309,7 +1309,7 @@
                                                legacyWait.always( function () {
                                                        if ( $.isArray( script ) ) {
                                                                nestedAddScript( script, markModuleReady, 0 );
-                                                       } else if ( $.isFunction( script ) ) {
+                                                       } else if ( typeof script === 'function' ) {
                                                                // Pass jQuery twice so that the signature of the closure which wraps
                                                                // the script can bind both '$' and 'jQuery'.
                                                                script( $, $, mw.loader.require, registry[ module ].module );
@@ -1547,13 +1547,18 @@
                         * @param {Array} modules Modules array
                         */
                        function resolveIndexedDependencies( modules ) {
-                               $.each( modules, function ( idx, module ) {
-                                       if ( module[ 2 ] ) {
-                                               module[ 2 ] = $.map( module[ 2 ], function ( dep ) {
-                                                       return typeof dep === 'number' ? modules[ dep ][ 0 ] : dep;
-                                               } );
+                               var i, j, deps;
+                               function resolveIndex( dep ) {
+                                       return typeof dep === 'number' ? modules[ dep ][ 0 ] : dep;
+                               }
+                               for ( i = 0; i < modules.length; i++ ) {
+                                       deps = modules[ i ][ 2 ];
+                                       if ( deps ) {
+                                               for ( j = 0; j < deps.length; j++ ) {
+                                                       deps[ j ] = resolveIndex( deps[ j ] );
+                                               }
                                        }
-                               } );
+                               }
                        }
 
                        /**
@@ -1798,7 +1803,7 @@
                                 * @param {string} [skip=null] Script body of the skip function
                                 */
                                register: function ( module, version, dependencies, group, source, skip ) {
-                                       var i;
+                                       var i, deps;
                                        // Allow multiple registration
                                        if ( typeof module === 'object' ) {
                                                resolveIndexedDependencies( module );
@@ -1816,6 +1821,13 @@
                                        if ( hasOwn.call( registry, module ) ) {
                                                throw new Error( 'module already registered: ' + module );
                                        }
+                                       if ( typeof dependencies === 'string' ) {
+                                               // A single module name
+                                               deps = [ dependencies ];
+                                       } else if ( typeof dependencies === 'object' || typeof dependencies === 'function' ) {
+                                               // Array of module names or a function that returns an array
+                                               deps = dependencies;
+                                       }
                                        // List the module as registered
                                        registry[ module ] = {
                                                // Exposed to execute() for mw.loader.implement() closures.
@@ -1824,20 +1836,12 @@
                                                        exports: {}
                                                },
                                                version: version !== undefined ? String( version ) : '',
-                                               dependencies: [],
+                                               dependencies: deps || [],
                                                group: typeof group === 'string' ? group : null,
                                                source: typeof source === 'string' ? source : 'local',
                                                state: 'registered',
                                                skip: typeof skip === 'string' ? skip : null
                                        };
-                                       if ( typeof dependencies === 'string' ) {
-                                               // Allow dependencies to be given as a single module name
-                                               registry[ module ].dependencies = [ dependencies ];
-                                       } else if ( typeof dependencies === 'object' || $.isFunction( dependencies ) ) {
-                                               // Allow dependencies to be given as an array of module names
-                                               // or a function which returns an array
-                                               registry[ module ].dependencies = dependencies;
-                                       }
                                },
 
                                /**
@@ -2023,14 +2027,11 @@
                                        if ( !hasOwn.call( registry, module ) ) {
                                                mw.loader.register( module );
                                        }
-                                       if ( $.inArray( state, [ 'ready', 'error', 'missing' ] ) !== -1
-                                               && registry[ module ].state !== state ) {
+                                       registry[ module ].state = state;
+                                       if ( $.inArray( state, [ 'ready', 'error', 'missing' ] ) !== -1 ) {
                                                // Make sure pending modules depending on this one get executed if their
                                                // dependencies are now fulfilled!
-                                               registry[ module ].state = state;
                                                handlePending( module );
-                                       } else {
-                                               registry[ module ].state = state;
                                        }
                                },
 
@@ -2275,6 +2276,7 @@
                                                        // Unversioned, private, or site-/user-specific
                                                        ( !descriptor.version || $.inArray( descriptor.group, [ 'private', 'user' ] ) !== -1 ) ||
                                                        // Partial descriptor
+                                                       // (e.g. skipped module, or style module with state=ready)
                                                        $.inArray( undefined, [ descriptor.script, descriptor.style,
                                                                        descriptor.messages, descriptor.templates ] ) !== -1
                                                ) {