From 77dc1ab675d6dfc59d0c5a47c81401b059fd8e4d Mon Sep 17 00:00:00 2001
From: Dzmitry Shylovich <Dzmitry_Shylovich@epam.com>
Date: Fri, 11 Nov 2016 01:55:10 +0300
Subject: [PATCH] fix(router): throw an error when encounter undefined route
 (#12389)

---
 modules/@angular/router/src/config.ts        | 18 +++++++++++++++++-
 modules/@angular/router/src/router_module.ts |  1 -
 modules/@angular/router/test/config.spec.ts  |  6 ++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/modules/@angular/router/src/config.ts b/modules/@angular/router/src/config.ts
index 06ea315763..1c1df4b5db 100644
--- a/modules/@angular/router/src/config.ts
+++ b/modules/@angular/router/src/config.ts
@@ -350,10 +350,26 @@ export interface Route {
 }
 
 export function validateConfig(config: Routes): void {
-  config.forEach(validateNode);
+  // forEach doesn't iterate undefined values
+  for (let i = 0; i < config.length; i++) {
+    validateNode(config[i]);
+  }
 }
 
 function validateNode(route: Route): void {
+  if (!route) {
+    throw new Error(`
+      Invalid route configuration: Encountered undefined route.
+      The reason might be an extra comma.
+       
+      Example: 
+      const routes: Routes = [
+        { path: '', redirectTo: '/dashboard', pathMatch: 'full' },
+        { path: 'dashboard',  component: DashboardComponent },, << two commas
+        { path: 'detail/:id', component: HeroDetailComponent }
+      ];
+    `);
+  }
   if (Array.isArray(route)) {
     throw new Error(`Invalid route configuration: Array cannot be specified`);
   }
diff --git a/modules/@angular/router/src/router_module.ts b/modules/@angular/router/src/router_module.ts
index 1c8d45e725..9144c820d6 100644
--- a/modules/@angular/router/src/router_module.ts
+++ b/modules/@angular/router/src/router_module.ts
@@ -8,7 +8,6 @@
 
 import {APP_BASE_HREF, HashLocationStrategy, Location, LocationStrategy, PathLocationStrategy, PlatformLocation} from '@angular/common';
 import {ANALYZE_FOR_ENTRY_COMPONENTS, APP_BOOTSTRAP_LISTENER, ApplicationRef, Compiler, Inject, Injector, ModuleWithProviders, NgModule, NgModuleFactoryLoader, OpaqueToken, Optional, Provider, SkipSelf, SystemJsNgModuleLoader} from '@angular/core';
-
 import {Route, Routes} from './config';
 import {RouterLink, RouterLinkWithHref} from './directives/router_link';
 import {RouterLinkActive} from './directives/router_link_active';
diff --git a/modules/@angular/router/test/config.spec.ts b/modules/@angular/router/test/config.spec.ts
index c77c50bdc7..7774b7d72b 100644
--- a/modules/@angular/router/test/config.spec.ts
+++ b/modules/@angular/router/test/config.spec.ts
@@ -15,6 +15,12 @@ describe('config', () => {
       validateConfig([{path: 'a', redirectTo: 'b'}, {path: 'b', component: ComponentA}]);
     });
 
+    it('should throw for undefined route', () => {
+      expect(() => {
+        validateConfig([{path: 'a', component: ComponentA}, , {path: 'b', component: ComponentB}]);
+      }).toThrowError();
+    });
+
     it('should throw when Array is passed', () => {
       expect(() => {
         validateConfig([