InjectionToken for config not working with AoT

Question

I'm writing an Angular library where I need to pass in a configuration object in the .forRoot() of the module import.

I'm trying to do this (the apparently correct way) with InjectionToken, but getting an AoT compilation error.

Error when compiling with AoT:

error TS4050: Return type of public static method from exported class has or is using name 'InjectionToken' from external module "/path/to/node_modules/@angular/core/src/di/injection_token" but cannot be named.

Any help is appreciated.

module.ts:

import { NgModule } from '@angular/core';
import { CONFIG, Config } from './config';

@NgModule({ ... })
export class SomeModule {
    static forRoot(config?: Config) {
        return {
            ngModule: SomeModule,
            providers: [
                { provide: CONFIG, useValue: config }
            ]
        };
    }
}

config.ts:

import { InjectionToken } from '@angular/core';

export const CONFIG = new InjectionToken<Config>('config');

export interface Config {
    some?: string;
    values?: string;
    here?: string;
}

Desired usage by another application:

import { NgModule } from '@angular/core';
import { SomeModule } from 'some-library';

@NgModule({
    imports: [
        SomeModule.forRoot({
            // <-- config values here
        })
    ]
})

(Angular 5, TypeScript 2.6.2)

This answer might be useful - https://stackoverflow.com/a/43293449/3055401 — Michael Doye, Jan 05 '18 at 18:24
Thanks, but that avoids the issue by getting rid of `InjectionToken`. From what I've read, best practice is to use `InjectionToken` over strings. — Mike, Jan 05 '18 at 18:26
My guess is that you must (and should anyway) specify the type returned by the forRoot method: `: ModuleWithProviders`. — JB Nizet, Jan 05 '18 at 20:34

score 2 · Accepted Answer · answered Jan 05 '18 at 20:45

Answer by JB Nizet in comments above...

Needed to specify the type returned by the forRoot method, ModuleWithProviders.

import { NgModule } from '@angular/core';
import { CONFIG, Config } from './config';

@NgModule({ ... })
export class SomeModule {
    static forRoot(config?: Config): ModuleWithProviders {
        return {
            ngModule: SomeModule,
            providers: [
                { provide: CONFIG, useValue: config }
            ]
        };
    }
}

InjectionToken for config not working with AoT

1 Answers1