[FEATURE ember-router-willtransition]

FEATURES.md

@@ -204,3 +204,17 @@ for a detailed explanation.
   ```
 
   Added in [#10160](https://github.com/emberjs/ember.js/pull/10160)
+
+* `ember-router-willtransition`
+
+  Adds `willTransition` hook to `Ember.Router`. For example,
+
+  ```js
+  Ember.Router.extend({
+    onBeforeTransition: function(transition) {
+      //doSomething
+    }.on('willTransition')
+  });
+  ```
+
+  Added in [#10274](https://github.com/emberjs/ember.js/pull/10274)

bower.json

@@ -8,7 +8,7 @@
   "devDependencies": {
     "backburner": "https://github.com/ebryn/backburner.js.git#f4bd6a2df221240ed36d140f0c53c036a7ecacad",
     "rsvp": "https://github.com/tildeio/rsvp.js.git#3.0.14",
-    "router.js": "https://github.com/tildeio/router.js.git#a1ffd97dc66a6d9d4e8dd89a72c1c4e21a3328c5",
+    "router.js": "https://github.com/tildeio/router.js.git#72eb0d336c1c3b7ad3965198b330fe148d935efe",
     "dag-map": "https://github.com/krisselden/dag-map.git#e307363256fe918f426e5a646cb5f5062d3245be",
     "ember-dev": "https://github.com/emberjs/ember-dev.git#1c30a1666273ab2a9b134a42bad28c774f9ecdfc"
   }

features.json

@@ -16,7 +16,8 @@
     "ember-metal-stream": null,
     "ember-htmlbars-each-with-index": true,
     "ember-application-instance-initializers": null,
-    "ember-application-initializer-context": null
+    "ember-application-initializer-context": null,
+    "ember-router-willtransition": true
   },
   "debugStatements": [
     "Ember.warn",

packages/ember-routing/lib/system/router.js

@@ -188,6 +188,24 @@ var EmberRouter = EmberObject.extend(Evented, {
     }
   },
 
+  /**
+    Handles notifying any listeners of an impending URL
+    change.
+
+    Triggers the router level `willTransition` hook.
+
+    @method willTransition
+    @private
+    @since 1.11.0
+  */
+  willTransition: function(oldInfos, newInfos, transition) {
+    run.once(this, this.trigger, 'willTransition', transition);
+
+    if (get(this, 'namespace').LOG_TRANSITIONS) {
+      Ember.Logger.log("Preparing to transition from '" + EmberRouter._routePath(oldInfos) + "' to '" + EmberRouter._routePath(newInfos) + "'");
+    }
+  },
+
   handleURL: function(url) {
     // Until we have an ember-idiomatic way of accessing #hashes, we need to
     // remove it because router.js doesn't know how to handle it.
@@ -419,6 +437,12 @@ var EmberRouter = EmberObject.extend(Evented, {
     router.didTransition = function(infos) {
       emberRouter.didTransition(infos);
     };
+
+    if (Ember.FEATURES.isEnabled('ember-router-willtransition')) {
+      router.willTransition = function(oldInfos, newInfos, transition) {
+        emberRouter.willTransition(oldInfos, newInfos, transition);
+      };
+    }
   },
 
   _serializeQueryParams: function(targetRouteName, queryParams) {

packages/ember/tests/routing/basic_test.js

@@ -2738,6 +2738,54 @@ test("Route silently fails when cleaning an outlet from an inactive view", funct
   Ember.run(function() { router.send('hideModal'); });
 });
 
+if (Ember.FEATURES.isEnabled('ember-router-willtransition')) {
+  test("Router `willTransition` hook passes in cancellable transition", function() {
+    // Should hit willTransition 3 times, once for the initial route, and then 2 more times
+    // for the two handleURL calls below
+    expect(3);
+
+    Router.map(function() {
+      this.route("nork");
+      this.route("about");
+    });
+
+    Router.reopen({
+      init: function() {
+        this._super();
+        this.on('willTransition', this.testWillTransitionHook);
+      },
+      testWillTransitionHook: function(transition, url) {
+        ok(true, "willTransition was called " + url);
+        transition.abort();
+      }
+    });
+
+    App.LoadingRoute = Ember.Route.extend({
+      activate: function() {
+        ok(false, "LoadingRoute was not entered");
+      }
+    });
+
+    App.NorkRoute = Ember.Route.extend({
+      activate: function() {
+        ok(false, "NorkRoute was not entered");
+      }
+    });
+
+    App.AboutRoute = Ember.Route.extend({
+      activate: function() {
+        ok(false, "AboutRoute was not entered");
+      }
+    });
+
+    bootApplication();
+
+    // Attempted transitions out of index should abort.
+    Ember.run(router, 'handleURL', '/nork');
+    Ember.run(router, 'handleURL', '/about');
+  });
+}
+
 test("Aborting/redirecting the transition in `willTransition` prevents LoadingRoute from being entered", function() {
   expect(8);