fix(select): Disallow keyboard selection of disabled options.

Although disabled options are not selectable via the mouse or arrow
keys, we currently allow users to select an option by typing the
first few letters. This logic did not account for disabled options.

Add a quick check to see if the requested option is disabled.

Fixes #8626.

Closes #8681

Author: topherfangio

src/components/select/select.js

@@ -517,7 +517,7 @@ function SelectDirective($mdSelect, $mdUtil, $mdTheming, $mdAria, $compile, $par
           if (e.keyCode <= 90 && e.keyCode >= 31) {
             e.preventDefault();
             var node = selectMenuCtrl.optNodeForKeyboardSearch(e);
-            if (!node) return;
+            if (!node || node.hasAttribute('disabled')) return;
             var optionCtrl = angular.element(node).controller('mdOption');
             if (!selectMenuCtrl.isMultiple) {
               selectMenuCtrl.deselect(Object.keys(selectMenuCtrl.selected)[0]);

src/components/select/select.spec.js

@@ -1098,6 +1098,16 @@ describe('<md-select>', function() {
         pressKey(el, 50);
         expect($rootScope.someModel).toBe(2);
       }));
+
+      it('disallows selection of disabled options', inject(function($rootScope) {
+        var optsTemplate =
+          '<md-option value="1">1</md-option>' +
+          '<md-option value="2" ng-disabled="true">2</md-option>';
+        var el = setupSelect('ng-model="someModel"', optsTemplate).find('md-select');
+
+        pressKey(el, 50);
+        expect($rootScope.someModel).toBe(undefined);
+      }));
     });
 
     describe('md-select-menu', function() {