feat($route): implement resolveRedirectTo

`resolveRedirectTo` can be set to a function that will (eventually) return the new URL to redirect
to. The function supports dependency injection and should return the new URL either as a string or
as a promise that will be resolved to a string.

If the `resolveRedirectTo` function returns `undefined` or returns a promise that gets resolved to
`undefined`, no redirection will take place and the current route will be processed normally.

If the `resolveRedirectTo` function throws an error or the returned promise gets rejected, no
further processing will take place (e.g. no template fetched, no `resolve` functions run, no
controller instantiated) and a `$routeChangeError` will be broadcasted.

`redirectTo` takes precedence over `resolveRedirectTo`, so specifying both on the same route
definition, will cause the latter to be ignored.

BREAKING CHANGE:

Previously, if `redirectTo` was a function that threw an Error, execution was aborted without firing
a `$routeChangeError` event.
Now, if a `redirectTo` function throws an Error, a `$routeChangeError` event will be fired.

Author: gkalpak

src/ngRoute/route.js

@@ -70,12 +70,12 @@ function $RouteProvider() {
    *
    *    Object properties:
    *
-   *    - `controller` – `{(string|function()=}` – Controller fn that should be associated with
+   *    - `controller` – `{(string|Function)=}` – Controller fn that should be associated with
    *      newly created scope or the name of a {@link angular.Module#controller registered
    *      controller} if passed as a string.
    *    - `controllerAs` – `{string=}` – An identifier name for a reference to the controller.
    *      If present, the controller will be published to scope under the `controllerAs` name.
-   *    - `template` – `{string=|function()=}` – html template as a string or a function that
+   *    - `template` – `{(string|Function)=}` – html template as a string or a function that
    *      returns an html template as a string which should be used by {@link
    *      ngRoute.directive:ngView ngView} or {@link ng.directive:ngInclude ngInclude} directives.
    *      This property takes precedence over `templateUrl`.
@@ -85,15 +85,15 @@ function $RouteProvider() {
    *      - `{Array.<Object>}` - route parameters extracted from the current
    *        `$location.path()` by applying the current route
    *
-   *    - `templateUrl` – `{string=|function()=}` – path or function that returns a path to an html
+   *    - `templateUrl` – `{(string|Function)=}` – path or function that returns a path to an html
    *      template that should be used by {@link ngRoute.directive:ngView ngView}.
    *
    *      If `templateUrl` is a function, it will be called with the following parameters:
    *
    *      - `{Array.<Object>}` - route parameters extracted from the current
    *        `$location.path()` by applying the current route
    *
-   *    - `resolve` - `{Object.<string, function>=}` - An optional map of dependencies which should
+   *    - `resolve` - `{Object.<string, Function>=}` - An optional map of dependencies which should
    *      be injected into the controller. If any of these dependencies are promises, the router
    *      will wait for them all to be resolved or one to be rejected before the controller is
    *      instantiated.
@@ -113,7 +113,7 @@ function $RouteProvider() {
    *      The map object is:
    *
    *      - `key` – `{string}`: a name of a dependency to be injected into the controller.
-   *      - `factory` - `{string|function}`: If `string` then it is an alias for a service.
+   *      - `factory` - `{string|Function}`: If `string` then it is an alias for a service.
    *        Otherwise if function, then it is {@link auto.$injector#invoke injected}
    *        and the return value is treated as the dependency. If the result is a promise, it is
    *        resolved before its value is injected into the controller. Be aware that
@@ -123,7 +123,7 @@ function $RouteProvider() {
    *    - `resolveAs` - `{string=}` - The name under which the `resolve` map will be available on
    *      the scope of the route. If omitted, defaults to `$resolve`.
    *
-   *    - `redirectTo` – `{(string|function())=}` – value to update
+   *    - `redirectTo` – `{(string|Function)=}` – value to update
    *      {@link ng.$location $location} path with and trigger route redirection.
    *
    *      If `redirectTo` is a function, it will be called with the following parameters:
@@ -134,14 +134,32 @@ function $RouteProvider() {
    *      - `{Object}` - current `$location.search()`
    *
    *      The custom `redirectTo` function is expected to return a string which will be used
-   *      to update `$location.path()` and `$location.search()`.
+   *      to update `$location.url()`. If the function throws an error, no further processing will
+   *      take place and the {@link ngRoute.$route#$routeChangeError $routeChangeError} event will
+   *      be fired.
    *
    *      Routes that specify `redirectTo` will not have their controllers, template functions
    *      or resolves called, the `$location` will be changed to the redirect url and route
    *      processing will stop. The exception to this is if the `redirectTo` is a function that
    *      returns `undefined`. In this case the route transition occurs as though there was no
    *      redirection.
    *
+   *    - `resolveRedirectTo` – `{Function=}` – a function that will (eventually) return the value
+   *      to update {@link ng.$location $location} URL with and trigger route redirection. In
+   *      contrast to `redirectTo`, dependencies can be injected into `resolveRedirectTo` and the
+   *      return value can be either a string or a promise that will be resolved to a string.
+   *
+   *      Similar to `redirectTo`, if the return value is `undefined` (or a promise that gets
+   *      resolved to `undefined`), no redirection takes place and the route transition occurs as
+   *      though there was no redirection.
+   *
+   *      If the function throws an error or the returned promise gets rejected, no further
+   *      processing will take place and the
+   *      {@link ngRoute.$route#$routeChangeError $routeChangeError} event will be fired.
+   *
+   *      `redirectTo` takes precedence over `resolveRedirectTo`, so specifying both on the same
+   *      route definition, will cause the latter to be ignored.
+   *
    *    - `[reloadOnSearch=true]` - `{boolean=}` - reload route when only `$location.search()`
    *      or `$location.hash()` changes.
    *
@@ -446,12 +464,14 @@ function $RouteProvider() {
      * @name $route#$routeChangeError
      * @eventType broadcast on root scope
      * @description
-     * Broadcasted if any of the resolve promises are rejected.
+     * Broadcasted if a redirection function fails or any redirection or resolve promises are
+     * rejected.
      *
      * @param {Object} angularEvent Synthetic event object
      * @param {Route} current Current route information.
      * @param {Route} previous Previous route information.
-     * @param {Route} rejection Rejection of the promise. Usually the error of the failed promise.
+     * @param {Route} rejection The thrown error or the rejection reason of the promise. Usually
+     * the rejection reason is the error that caused the promise to get rejected.
      */
 
     /**
@@ -592,44 +612,103 @@ function $RouteProvider() {
       } else if (nextRoute || lastRoute) {
         forceReload = false;
         $route.current = nextRoute;
-        if (nextRoute) {
-          if (nextRoute.redirectTo) {
-            var url = $location.url();
-            var newUrl;
-            if (angular.isString(nextRoute.redirectTo)) {
-              $location.path(interpolate(nextRoute.redirectTo, nextRoute.params))
-                       .search(nextRoute.params)
-                       .replace();
-              newUrl = $location.url();
-            } else {
-              newUrl = nextRoute.redirectTo(nextRoute.pathParams, $location.path(), $location.search());
-              $location.url(newUrl).replace();
-            }
-            if (angular.isDefined(newUrl) && url !== newUrl) {
-              return; //exit out and don't process current next value, wait for next location change from redirect
-            }
-          }
-        }
 
-        $q.when(nextRoute).
-          then(resolveLocals).
-          then(function(locals) {
-            // after route change
-            if (nextRoute === $route.current) {
-              if (nextRoute) {
-                nextRoute.locals = locals;
-                angular.copy(nextRoute.params, $routeParams);
-              }
-              $rootScope.$broadcast('$routeChangeSuccess', nextRoute, lastRoute);
-            }
-          }, function(error) {
+        var nextRoutePromise = $q.resolve(nextRoute);
+
+        nextRoutePromise.
+          then(getRedirectionData).
+          then(handlePossibleRedirection).
+          then(function(keepProcessingRoute) {
+            return keepProcessingRoute && nextRoutePromise.
+              then(resolveLocals).
+              then(function(locals) {
+                // after route change
+                if (nextRoute === $route.current) {
+                  if (nextRoute) {
+                    nextRoute.locals = locals;
+                    angular.copy(nextRoute.params, $routeParams);
+                  }
+                  $rootScope.$broadcast('$routeChangeSuccess', nextRoute, lastRoute);
+                }
+              });
+          }).catch(function(error) {
             if (nextRoute === $route.current) {
               $rootScope.$broadcast('$routeChangeError', nextRoute, lastRoute, error);
             }
           });
       }
     }
 
+    function getRedirectionData(route) {
+      var data = {
+        route: route,
+        hasRedirection: false
+      };
+
+      if (route) {
+        if (route.redirectTo) {
+          if (angular.isString(route.redirectTo)) {
+            data.path = interpolate(route.redirectTo, route.params);
+            data.search = route.params;
+            data.hasRedirection = true;
+          } else {
+            var oldPath = $location.path();
+            var oldSearch = $location.search();
+            var newUrl = route.redirectTo(route.pathParams, oldPath, oldSearch);
+
+            if (angular.isDefined(newUrl)) {
+              data.url = newUrl;
+              data.hasRedirection = true;
+            }
+          }
+        } else if (route.resolveRedirectTo) {
+          return $q.
+            resolve($injector.invoke(route.resolveRedirectTo)).
+            then(function(newUrl) {
+              if (angular.isDefined(newUrl)) {
+                data.url = newUrl;
+                data.hasRedirection = true;
+              }
+
+              return data;
+            });
+        }
+      }
+
+      return data;
+    }
+
+    function handlePossibleRedirection(data) {
+      var keepProcessingRoute = true;
+
+      if (data.route !== $route.current) {
+        keepProcessingRoute = false;
+      } else if (data.hasRedirection) {
+        var oldUrl = $location.url();
+        var newUrl = data.url;
+
+        if (newUrl) {
+          $location.
+            url(newUrl).
+            replace();
+        } else {
+          newUrl = $location.
+            path(data.path).
+            search(data.search).
+            replace().
+            url();
+        }
+
+        if (newUrl !== oldUrl) {
+          // Exit out and don't process current next value,
+          // wait for next location change from redirect
+          keepProcessingRoute = false;
+        }
+      }
+
+      return keepProcessingRoute;
+    }
+
     function resolveLocals(route) {
       if (route) {
         var locals = angular.extend({}, route.resolve);
@@ -646,7 +725,6 @@ function $RouteProvider() {
       }
     }
 
-
     function getTemplateFor(route) {
       var template, templateUrl;
       if (angular.isDefined(template = route.template)) {
@@ -665,7 +743,6 @@ function $RouteProvider() {
       return template;
     }
 
-
     /**
      * @returns {Object} the current active route, by matching it against the URL
      */