fix 1699: support preventDefault() for $routeChangeStart

src/ng/route.js

@@ -275,6 +275,11 @@ function $RouteProvider(){
      * defined in `resolve` route property. Once  all of the dependencies are resolved
      * `$routeChangeSuccess` is fired.
      *
+     * Call event.preventDefault() to prevent changing route but leave the browser Url
+     * to it's new location (as opposed to calling event.preventDefault() on $location's
+     * $locationChangeStart event which cancels changing the browser's Url).
+     *
+     *
      * @param {Route} next Future route information.
      * @param {Route} current Current route information.
      */
@@ -405,7 +410,9 @@ function $RouteProvider(){
         $rootScope.$broadcast('$routeUpdate', last);
       } else if (next || last) {
         forceReload = false;
-        $rootScope.$broadcast('$routeChangeStart', next, last);
+        if ( $rootScope.$broadcast('$routeChangeStart', next, last).defaultPrevented ){
+          return;
+        }
         $route.current = next;
         if (next) {
           if (next.redirectTo) {

test/ng/routeSpec.js

@@ -205,6 +205,28 @@ describe('$route', function() {
   });
 
 
+  it('should not change route when $routeChangeStart is canceled', function() {
+    module(function($routeProvider) {
+      $routeProvider.when('/somePath', {template: 'some path'});
+    });
+    inject(function($route, $location, $rootScope, $log) {
+      $rootScope.$on('$routeChangeStart', function(event) {
+        $log.info('$routeChangeStart');
+        event.preventDefault();
+      });
+
+      $rootScope.$on('$routeChangeSuccess', function(event) {
+        throw new Error('Should not get here');
+      });
+
+      $location.path('/somePath');
+      $rootScope.$digest();
+
+      expect($log.info.logs.shift()).toEqual(['$routeChangeStart']);
+    });
+  });
+
+
   describe('should match a route that contains special chars in the path', function() {
     beforeEach(module(function($routeProvider) {
       $routeProvider.when('/$test.23/foo*(bar)/:baz', {templateUrl: 'test.html'});