feat(router): implement CandDeactivate

modules/@angular/router/src/router_state.ts

@@ -1,4 +1,5 @@
 import { Tree, TreeNode } from './utils/tree';
+import { shallowEqual } from './utils/collection';
 import { UrlSegment } from './url_tree';
 import { Route } from './config';
 import { Params, PRIMARY_OUTLET } from './shared';
@@ -34,6 +35,7 @@ export function createEmptyState(rootComponent: Type): RouterState {
   const emptyQueryParams = new BehaviorSubject({});
   const fragment = new BehaviorSubject("");
   const activated = new ActivatedRoute(emptyUrl, emptyParams, PRIMARY_OUTLET, rootComponent, snapshot.root);
+  activated.snapshot = snapshot.root;
   return new RouterState(new TreeNode<ActivatedRoute>(activated, []), emptyQueryParams, fragment, snapshot);
 }
 
@@ -62,12 +64,18 @@ function createEmptyStateSnapshot(rootComponent: Type): RouterStateSnapshot {
  * ```
  */
 export class ActivatedRoute {
+  /** @internal */
+  _futureSnapshot: ActivatedRouteSnapshot;
+  snapshot: ActivatedRouteSnapshot;
+
   constructor(public urlSegments: Observable<UrlSegment[]>,
               public params: Observable<Params>,
               public outlet: string,
               public component: Type | string,
-              public snapshot: ActivatedRouteSnapshot
-  ) {}
+              futureSnapshot: ActivatedRouteSnapshot
+  ) {
+    this._futureSnapshot = futureSnapshot;
+  }
 }
 
 /**
@@ -123,4 +131,19 @@ export class RouterStateSnapshot extends Tree<ActivatedRouteSnapshot> {
   constructor(root: TreeNode<ActivatedRouteSnapshot>, public queryParams: Params, public fragment: string | null) {
     super(root);
   }
+}
+
+/**
+ * The expectation is that the activate route is created with the right set of parameters.
+ * So we push new values into the observables only when they are not the initial values.
+ * And we detect that by checking if the snapshot field is set.
+ */
+export function advanceActivatedRoute(route: ActivatedRoute): void {
+  if (route.snapshot && !shallowEqual(route.snapshot.params, route._futureSnapshot.params)) {
+    route.snapshot = route._futureSnapshot;
+    (<any>route.urlSegments).next(route.snapshot.urlSegments);
+    (<any>route.params).next(route.snapshot.params);
+  } else {
+    route.snapshot = route._futureSnapshot;
+  }
 }