feat(store): throw error when forRoot() is used more than once

Author: timdeschryver

modules/store/spec/integration.spec.ts

@@ -21,6 +21,12 @@ import {
   visibilityFilter,
   VisibilityFilters,
 } from './fixtures/todos';
+import {
+  RouterTestingModule,
+  SpyNgModuleFactoryLoader,
+} from '@angular/router/testing';
+import { Component, NgModuleFactoryLoader, NgModule } from '@angular/core';
+import { Router } from '@angular/router';
 
 interface Todo {
   id: number;
@@ -478,5 +484,31 @@ describe('ngRx Integration spec', () => {
         expect(state).toEqual(expected);
       });
     });
+
+    it('throws if forRoot() is used more than once', (done: DoneFn) => {
+      @NgModule({
+        imports: [StoreModule.forRoot({})],
+      })
+      class FeatureModule {}
+
+      TestBed.configureTestingModule({
+        imports: [StoreModule.forRoot({}), RouterTestingModule.withRoutes([])],
+      });
+
+      let router: Router = TestBed.get(Router);
+      const loader: SpyNgModuleFactoryLoader = TestBed.get(
+        NgModuleFactoryLoader
+      );
+
+      loader.stubbedModules = { feature: FeatureModule };
+      router.resetConfig([{ path: 'feature-path', loadChildren: 'feature' }]);
+
+      router.navigateByUrl('/feature-path').catch((err: TypeError) => {
+        expect(err.message).toBe(
+          'StoreModule.forRoot() called twice. Feature modules should use StoreModule.forFeature() instead.'
+        );
+        done();
+      });
+    });
   });
 });

modules/store/src/store_module.ts

@@ -5,6 +5,8 @@ import {
   OnDestroy,
   InjectionToken,
   Injector,
+  Optional,
+  SkipSelf,
 } from '@angular/core';
 import {
   Action,
@@ -16,7 +18,7 @@ import {
   MetaReducer,
   RuntimeChecks,
 } from './models';
-import { compose, combineReducers, createReducerFactory } from './utils';
+import { combineReducers, createReducerFactory } from './utils';
 import {
   INITIAL_STATE,
   INITIAL_REDUCERS,
@@ -34,6 +36,7 @@ import {
   _FEATURE_CONFIGS,
   USER_PROVIDED_META_REDUCERS,
   _RESOLVED_META_REDUCERS,
+  _ROOT_STORE_GUARD,
 } from './tokens';
 import { ACTIONS_SUBJECT_PROVIDERS, ActionsSubject } from './actions_subject';
 import {
@@ -55,7 +58,10 @@ export class StoreRootModule {
     actions$: ActionsSubject,
     reducer$: ReducerObservable,
     scannedActions$: ScannedActionsSubject,
-    store: Store<any>
+    store: Store<any>,
+    @Optional()
+    @Inject(_ROOT_STORE_GUARD)
+    guard: any
   ) {}
 }
 
@@ -112,6 +118,11 @@ export class StoreModule {
     return {
       ngModule: StoreRootModule,
       providers: [
+        {
+          provide: _ROOT_STORE_GUARD,
+          useFactory: _provideForRootGuard,
+          deps: [[Store, new Optional(), new SkipSelf()]],
+        },
         { provide: _INITIAL_STATE, useValue: config.initialState },
         {
           provide: INITIAL_STATE,
@@ -285,3 +296,12 @@ export function _concatMetaReducers(
 ): MetaReducer[] {
   return metaReducers.concat(userProvidedMetaReducers);
 }
+
+export function _provideForRootGuard(store: Store<any>): any {
+  if (store) {
+    throw new TypeError(
+      `StoreModule.forRoot() called twice. Feature modules should use StoreModule.forFeature() instead.`
+    );
+  }
+  return 'guarded';
+}

modules/store/src/tokens.ts

@@ -1,6 +1,9 @@
 import { InjectionToken } from '@angular/core';
 import { RuntimeChecks, MetaReducer } from './models';
 
+export const _ROOT_STORE_GUARD = new InjectionToken<void>(
+  '@ngrx/store Internal Root Guard'
+);
 export const _INITIAL_STATE = new InjectionToken(
   '@ngrx/store Internal Initial State'
 );