Merge "mw.widgets.CategorySelector: Prevent duplicates"

diff --combined resources/src/mediawiki.widgets/mw.widgets.CategorySelector.js
index e0bbf22,1e65da5..510068a
--- 1/resources/src/mediawiki.widgets/mw.widgets.CategorySelector.js
--- 2/resources/src/mediawiki.widgets/mw.widgets.CategorySelector.js
+++ b/resources/src/mediawiki.widgets/mw.widgets.CategorySelector.js
@@@ -134,7 -134,7 +134,7 @@@
        CSP.getNewMenuItems = function ( input ) {
                var i,
                        promises = [],
 -                      deferred = new $.Deferred();
 +                      deferred = $.Deferred();
  
                if ( $.trim( input ) === '' ) {
                        deferred.resolve( [] );
@@@ -184,6 -184,16 +184,16 @@@
                } );
        };
  
+       /**
+        * @inheritdoc
+        */
+       CSP.getItemFromData = function ( data ) {
+               // This is a bit of a hack... We have to canonicalize the data in the same way that
+               // #createItemWidget and CategoryCapsuleItemWidget will do, otherwise we won't find duplicates.
+               data = mw.Title.newFromText( data, NS_CATEGORY ).getMainText();
+               return OO.ui.mixin.GroupElement.prototype.getItemFromData.call( this, data );
+       };
+ 
        /**
         * Validates the values in `this.searchType`.
         *
@@@ -242,7 -252,7 +252,7 @@@
         * @return {jQuery.Promise} Resolves with an array of categories
         */
        CSP.searchCategories = function ( input, searchType ) {
 -              var deferred = new $.Deferred();
 +              var deferred = $.Deferred();
  
                switch ( searchType ) {
                        case CategorySelector.SearchType.OpenSearch: