fix(list): case where list items are read twice by screen readers

- if we create an `aria-label` from the element's text content
  then mark the content as `aria-hidden="true"` so that screen
  readers don't announce/traverse the content twice
- improve Closure types

Fixes #11582

src/components/list/list.js

@@ -343,16 +343,21 @@ function mdListItemDirective($mdAria, $mdConstant, $mdUtil, $timeout) {
           );
 
           // Button which shows ripple and executes primary action.
-          var buttonWrap = angular.element(
-            '<md-button class="md-no-style"></md-button>'
-          );
+          var buttonWrap = angular.element('<md-button class="md-no-style"></md-button>');
 
           moveAttributes(tElement[0], buttonWrap[0]);
 
           // If there is no aria-label set on the button (previously copied over if present)
           // we determine the label from the content and copy it to the button.
           if (!buttonWrap.attr('aria-label')) {
             buttonWrap.attr('aria-label', $mdAria.getText(tElement));
+
+            // If we set the button's aria-label to the text content, then make the content hidden
+            // from screen readers so that it isn't read/traversed twice.
+            var listItemInner = itemContainer[0].querySelector('.md-list-item-inner');
+            if (listItemInner) {
+              listItemInner.setAttribute('aria-hidden', 'true');
+            }
           }
 
           // We allow developers to specify the `md-no-focus` class, to disable the focus style
@@ -386,7 +391,7 @@ function mdListItemDirective($mdAria, $mdConstant, $mdUtil, $timeout) {
 
       /**
        * @param {HTMLElement} secondaryItem
-       * @param container
+       * @param {HTMLDivElement} container
        */
       function wrapSecondaryItem(secondaryItem, container) {
         // If the current secondary item is not a button, but contains a ng-click attribute,
@@ -423,9 +428,9 @@ function mdListItemDirective($mdAria, $mdConstant, $mdUtil, $timeout) {
        * Moves attributes from a source element to the destination element.
        * By default, the function will copy the most necessary attributes, supported
        * by the button executor for clickable list items.
-       * @param source Element with the specified attributes
-       * @param destination Element which will receive the attributes
-       * @param extraAttrs Additional attributes, which will be moved over
+       * @param {Element} source Element with the specified attributes
+       * @param {Element} destination Element which will receive the attributes
+       * @param {string|string[]} extraAttrs Additional attributes, which will be moved over
        */
       function moveAttributes(source, destination, extraAttrs) {
         var copiedAttrs = $mdUtil.prefixer([

src/components/list/list.spec.js

@@ -512,10 +512,12 @@ describe('mdListItem directive', function() {
     it('should copy label to the button executor element', function() {
       var listItem = setup('<md-list-item ng-click="null" aria-label="Test">');
       var buttonEl = listItem.find('button');
+      var listItemInnerElement = listItem[0].querySelector('.md-list-item-inner');
 
       // The aria-label attribute should be moved to the button element.
       expect(buttonEl.attr('aria-label')).toBe('Test');
       expect(listItem.attr('aria-label')).toBeFalsy();
+      expect(listItemInnerElement.getAttribute('aria-hidden')).toBeFalsy();
     });
 
     it('should determine the label from the content if not set', function() {
@@ -527,9 +529,11 @@ describe('mdListItem directive', function() {
       );
 
       var buttonEl = listItem.find('button');
+      var listItemInnerElement = listItem[0].querySelector('.md-list-item-inner');
 
       // The aria-label attribute should be determined from the content.
       expect(buttonEl.attr('aria-label')).toBe('Content');
+      expect(listItemInnerElement.getAttribute('aria-hidden')).toBeTruthy();
     });
 
     it('should determine the label from the bound content if aria-label is not set', function() {

src/core/services/aria/aria.js

@@ -128,9 +128,13 @@ function MdAriaService($$rAF, $log, $window, $interpolate) {
     }
   }
 
+  /**
+   * @param {Element|JQLite} element
+   * @returns {string}
+   */
   function getText(element) {
     element = element[0] || element;
-    var walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT, null, false);
+    var walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT, null);
     var text = '';
 
     var node;
@@ -142,6 +146,10 @@ function MdAriaService($$rAF, $log, $window, $interpolate) {
 
     return text.trim() || '';
 
+    /**
+     * @param {Node} node
+     * @returns {boolean}
+     */
     function isAriaHiddenNode(node) {
       while (node.parentNode && (node = node.parentNode) !== element) {
         if (node.getAttribute && node.getAttribute('aria-hidden') === 'true') {