From: Timo Tijhof <krinklemail@gmail.com>
Date: Fri, 26 Aug 2016 04:51:01 +0000 (-0700)
Subject: mw.loader: Make 'mwLoadEnd' less expensive with a single using()
X-Git-Tag: 1.31.0-rc.0~5348^2~2
X-Git-Url: https://git.cyclocoop.org/%7B%24www_url%7Dadmin/compta/banques/ajouter.php?a=commitdiff_plain;h=2bdd56e89334d85c48753b0052b0a94689dd584b;p=lhc%2Fweb%2Fwiklou.git

mw.loader: Make 'mwLoadEnd' less expensive with a single using()

20-30ms before this patch, ~2ms after this patch (MacBookPro, Chrome 52).

The creation of 100s of Deferred objects, $.when() tracking them
all, and bubbling up the completion took 20-30ms. This is quite
expensive. Optimise by using a single deferred first.
A module reaching state 'missing' or 'error' is very rare.

Change-Id: I90eea4bfe8fe6d85c395d9d0868bbde482c4a703
---

diff --git a/resources/src/mediawiki/mediawiki.js b/resources/src/mediawiki/mediawiki.js
index af37162cbe..7ceb5fe9ee 100644
--- a/resources/src/mediawiki/mediawiki.js
+++ b/resources/src/mediawiki/mediawiki.js
@@ -2693,14 +2693,18 @@
 		var loading = $.grep( mw.loader.getModuleNames(), function ( module ) {
 			return mw.loader.getState( module ) === 'loading';
 		} );
-		// In order to use jQuery.when (which stops early if one of the promises got rejected)
-		// cast any loading failures into successes. We only need a callback, not the module.
-		loading = $.map( loading, function ( module ) {
-			return mw.loader.using( module ).then( null, function () {
-				return $.Deferred().resolve();
+		// We only need a callback, not any actual module. First try a single using()
+		// for all loading modules. If one fails, fall back to tracking each module
+		// separately via $.when(), this is expensive.
+		loading = mw.loader.using( loading ).then( null, function () {
+			var all = $.map( loading, function ( module ) {
+				return mw.loader.using( module ).then( null, function () {
+					return $.Deferred().resolve();
+				} );
 			} );
+			return $.when.apply( $, all );
 		} );
-		$.when.apply( $, loading ).then( function () {
+		loading.then( function () {
 			mwPerformance.mark( 'mwLoadEnd' );
 			mw.hook( 'resourceloader.loadEnd' ).fire();
 		} );