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December 20, 2023 18:31
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Angular `makeForRootGuard` helper
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| import { | |
| FactoryProvider, | |
| InjectionToken, | |
| Optional, | |
| SkipSelf, | |
| Type, | |
| } from '@angular/core' | |
| /** | |
| * Helps to make a `forRoot` guard to ensure a module is not imported | |
| * multiple times using `forRoot` | |
| * | |
| * Usage: | |
| * | |
| * ``` | |
| * const [FOR_ROOT_GUARD_TOKEN, FOR_ROOT_GUARD_PROVIDER] = makeForRootGuard( | |
| * 'module name', | |
| * [ToBeGuardedService, ToBeGuardedToken] | |
| * ) | |
| * | |
| * // In module's constructor: | |
| * constructor(@Optional() @Inject(FOR_ROOT_GUARD_TOKEN) guard: unknown) {} | |
| * | |
| * // In module's `forRoot` providers: | |
| * const providers = [ | |
| * FOR_ROOT_GUARD_PROVIDER | |
| * ] | |
| * ``` | |
| * | |
| * @see https://github.com/angular/angular/blob/17.0.3/packages/router/src/router_module.ts#L34-L39 | |
| * @see https://github.com/angular/angular/blob/17.0.3/packages/router/src/router_module.ts#L84 | |
| * @see https://github.com/angular/angular/blob/17.0.3/packages/router/src/router_module.ts#L113-L117 | |
| * @see https://github.com/angular/angular/blob/17.0.3/packages/router/src/router_module.ts#L187-L195 | |
| */ | |
| export const makeForRootGuard = ( | |
| moduleName: string, | |
| ...depsToGuard: (InjectionToken<unknown> | Type<unknown>)[] | |
| ): [InjectionToken<void>, FactoryProvider] => { | |
| const injectionToken = new InjectionToken<void>( | |
| `${moduleName} forRoot() guard`, | |
| ) | |
| if (depsToGuard.length === 0) { | |
| depsToGuard.push(injectionToken) | |
| } | |
| const provider: FactoryProvider = { | |
| provide: injectionToken, | |
| useFactory: (...depsToGuard: unknown[]) => { | |
| const definedDependencies = depsToGuard.filter( | |
| (depToGuard) => !!depToGuard, | |
| ) | |
| if (definedDependencies.length > 0) { | |
| throw new Error( | |
| `One or more dependencies for ${moduleName} was provided ` + | |
| 'more than once. This can happen if `forRoot` is used outside of ' + | |
| 'the root injector', | |
| ) | |
| } | |
| }, | |
| deps: depsToGuard.map((depToGuard) => [ | |
| depToGuard, | |
| new Optional(), | |
| new SkipSelf(), | |
| ]), | |
| } | |
| return [injectionToken, provider] | |
| } |
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