Always display assistant languages where available

Assistant languages are chosen by users in a wiki with
Translate extension. If assistant languages are defined,
use that also for predicting the languages in compact list.

Bug: 62342
Change-Id: I25f42f3802e80baf5d4724ba6e42e00b8be2349e

resources/js/ext.uls.compactlinks.js

@@ -174,6 +174,9 @@
 		compact: function ( languages ) {
 			var compactLanguages = [];
 
+			// Add user-defined assistant languages on wikis with Translate extension.
+			compactLanguages = compactLanguages.concat( this.filterByAssistantLanguages() );
+
 			// Add previously selected languages.
 			// Previous languages are always the better suggestion
 			// because the user has explicitly chosen them.
@@ -223,6 +226,23 @@
 			} );
 		},
 
+		/**
+		 * Filter the language list by Translate's assistant languages.
+		 * Where available, they're languages deemed useful by the user.
+		 * @return {Array} List of those language codes which are supported by article
+		 */
+		filterByAssistantLanguages: function ( languages ) {
+			var assistantLanguages = mw.user.options.get( 'translate-editlangs' );
+
+			if ( assistantLanguages && assistantLanguages !== 'default' ) {
+				return $.grep( assistantLanguages.split(/,\s*/), function ( language ) {
+					return $.inArray( language, languages ) >= 0;
+				} );
+			}
+
+			return [];
+		},
+
 		/**
 		 * Find out the existing languages supported
 		 * by the article and fetch their href.