refactor(router): Warn when provideRoutes is used without provideRouter (#47896)

Due to being only 1 letter away from `provideRouter`, it is quite
possible that developers may accidentally use `provideRoutes` rather
than `provideRouter` in the `boostrapApplication` function. This change
will warn developers when `provideRoutes` is used without the `Router`.

PR Close #47896

packages/core/test/bundling/router/bundle.golden_symbols.json

@@ -1577,9 +1577,6 @@
   {
     "name": "promise"
   },
-  {
-    "name": "provideRoutes"
-  },
   {
     "name": "redirectIfUrlTree"
   },
@@ -1640,6 +1637,9 @@
   {
     "name": "rootRoute"
   },
+  {
+    "name": "routes"
+  },
   {
     "name": "rxSubscriber"
   },

packages/router/src/provide_router.ts

@@ -61,6 +61,7 @@ const NG_DEV_MODE = typeof ngDevMode === 'undefined' || ngDevMode;
 export function provideRouter(routes: Routes, ...features: RouterFeatures[]): EnvironmentProviders {
   return makeEnvironmentProviders([
     {provide: ROUTES, multi: true, useValue: routes},
+    NG_DEV_MODE ? {provide: ROUTER_IS_PROVIDED, useValue: true} : [],
     {provide: ActivatedRoute, useFactory: rootRoute, deps: [Router]},
     {provide: APP_BOOTSTRAP_LISTENER, multi: true, useFactory: getBootstrapListener},
     features.map(feature => feature.ɵproviders),
@@ -93,6 +94,28 @@ function routerFeature<FeatureKind extends RouterFeatureKind>(
   return {ɵkind: kind, ɵproviders: providers};
 }
 
+
+/**
+ * An Injection token used to indicate whether `provideRouter` or `RouterModule.forRoot` was ever
+ * called.
+ */
+export const ROUTER_IS_PROVIDED =
+    new InjectionToken<boolean>('', {providedIn: 'root', factory: () => false});
+
+const routerIsProvidedDevModeCheck = {
+  provide: ENVIRONMENT_INITIALIZER,
+  multi: true,
+  useFactory() {
+    return () => {
+      if (!inject(ROUTER_IS_PROVIDED)) {
+        console.warn(
+            '`provideRoutes` was called without `provideRouter` or `RouterModule.forRoot`. ' +
+            'This is likely a mistake.');
+      }
+    };
+  }
+};
+
 /**
  * Registers a [DI provider](guide/glossary#provider) for a set of routes.
  * @param routes The route configuration to provide.
@@ -113,6 +136,7 @@ function routerFeature<FeatureKind extends RouterFeatureKind>(
 export function provideRoutes(routes: Routes): Provider[] {
   return [
     {provide: ROUTES, multi: true, useValue: routes},
+    NG_DEV_MODE ? routerIsProvidedDevModeCheck : [],
   ];
 }
 

packages/router/src/router_module.ts

@@ -15,7 +15,7 @@ import {RouterLinkActive} from './directives/router_link_active';
 import {RouterOutlet} from './directives/router_outlet';
 import {RuntimeErrorCode} from './errors';
 import {Routes} from './models';
-import {getBootstrapListener, rootRoute, withDebugTracing, withDisabledInitialNavigation, withEnabledBlockingInitialNavigation, withPreloading} from './provide_router';
+import {getBootstrapListener, rootRoute, ROUTER_IS_PROVIDED, withDebugTracing, withDisabledInitialNavigation, withEnabledBlockingInitialNavigation, withPreloading} from './provide_router';
 import {Router, setupRouter} from './router';
 import {ExtraOptions, ROUTER_CONFIGURATION} from './router_config';
 import {RouterConfigLoader, ROUTES} from './router_config_loader';
@@ -48,6 +48,9 @@ export const ROUTER_PROVIDERS: Provider[] = [
   ChildrenOutletContexts,
   {provide: ActivatedRoute, useFactory: rootRoute, deps: [Router]},
   RouterConfigLoader,
+  // Only used to warn when `provideRoutes` is used without `RouterModule` or `provideRouter`. Can
+  // be removed when `provideRoutes` is removed.
+  NG_DEV_MODE ? {provide: ROUTER_IS_PROVIDED, useValue: true} : [],
 ];
 
 export function routerNgProbeToken() {

packages/router/test/standalone.spec.ts

@@ -9,9 +9,8 @@
 import {Component, Injectable, NgModule} from '@angular/core';
 import {ComponentFixture, fakeAsync, TestBed, tick} from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
-import {NavigationEnd, Router, RouterModule} from '@angular/router';
+import {provideRoutes, Router, RouterModule, ROUTES} from '@angular/router';
 import {RouterTestingModule} from '@angular/router/testing';
-import {filter, first} from 'rxjs/operators';
 
 @Component({template: '<div>simple standalone</div>', standalone: true})
 export class SimpleStandaloneComponent {
@@ -372,6 +371,16 @@ describe('standalone in Router API', () => {
   });
 });
 
+describe('provideRoutes', () => {
+  it('warns if provideRoutes is used without provideRouter, RouterTestingModule, or RouterModule.forRoot',
+     () => {
+       spyOn(console, 'warn');
+       TestBed.configureTestingModule({providers: [provideRoutes([])]});
+       TestBed.inject(ROUTES);
+       expect(console.warn).toHaveBeenCalled();
+     });
+});
+
 function advance(fixture: ComponentFixture<unknown>) {
   tick();
   fixture.detectChanges();