So i have a Nest application and have gotten stuck on what feels like a very basic issue.
I need to use the PlaceVerificationRequestService in the PlaceService but cant inject it properly without receiving the following error:
Nest can't resolve dependencies of the PlaceService (PlaceRepository, ClientService, ?). Please make sure that the argument dependency at index [2] is available in the PlaceModule context.
My approach has been to just follow the same style as i did when importing & injecting the ClientService in to PlaceService but still it does not work and i cant figure out why.
This is my code.
place.module.ts
@Module({
imports: [
MikroOrmModule.forFeature({
entities: [Place, Client, PlaceVerificationRequest],
}),
],
providers: [PlaceService, ClientService, PlaceVerificationRequestService],
controllers: [PlaceController],
exports: [PlaceService],
})
place-verification-request.module.ts
@Module({
imports: [
MikroOrmModule.forFeature({
entities: [PlaceVerificationRequest, Client, Place],
}),
],
providers: [PlaceVerificationRequestService, ClientService, PlaceService],
controllers: [PlaceVerificationRequestController],
exports: [PlaceVerificationRequestService],
})
place.service.ts
@Injectable()
export class PlaceService {
constructor(
@InjectRepository(Place)
private readonly placeRepo: EntityRepository<Place>,
private readonly clientService: ClientService,
private readonly reqService: PlaceVerificationRequestService,
) {}
It feels like im missing something that is right in front of my nose since it feels very basic but i cant seem to spot it. Anyone that has a clue? thanks
Okay after 5 hours, the trick is... to read the docs.
Nest can't resolve dependencies of the <provider> (?). Please make sure that the argument <unknown_token> at index [<index>] is available in the <module> context.
Potential solutions:
- If <unknown_token> is a provider, is it part of the current <module>?
- If <unknown_token> is exported from a separate @Module, is that module imported within <module>?
@Module({
imports: [ /* the Module containing <unknown_token> */ ]
})
If the unknown_token above is the string dependency, you might have a circular file import.
(gotta admit they could've come up with a clearer error message)
So basically the problem was that PlaceService was getting injected in PlaceVerificationRequestService and PlaceVerificationRequestService was getting injected in PlaceService so the trick is to use forwardRef:
PlaceVerificationRequestService
@Inject(forwardRef(() => PlaceService))
private readonly placeService: PlaceService,
PlaceService
@Inject(forwardRef(() => PlaceVerificationRequestService))
private readonly reqService: PlaceVerificationRequestService,
Nest cannot figure out how to create a copy of the PlaceService because you have not provided all the different dependencies of the PlaceService.
That's why it asks is the <unknown_token> a provider? In other words, does the PlaceService need a copy of this unknown_token? Now that does not make sense to me, so what it probably wants to ask you is does it need a copy of that Place Verification Request Service, but the way you wrote this is giving you a confusing prompt, you know we get out of it what we put into it, so the error is not confusing, we just gave it something that made it give us a confusing prompt.
You can try to write a test for this by doing something like this for example:
import { Test } from '@nestjs/testing';
import { PlaceService } from './place/service';
import { PlaceVerificationRequestService } from './place-verification-request.service';
it('can create an instance of place service', async () => {
// Create a fake copy of the place verification request service
const fakePlaceVerificationRequestService = {
find: () => Promise.resolve([])
// add properties of the service as arguments
create: () => Promise.resolve()
};
const module = await Test.createTestingModule({
providers: [
PlaceService,
{
provide: PlaceVerificationRequestService,
useValue: fakePlaceVerificationRequestService
}
],
}).compile();
const service = module.get(PlaceService);
expect(service).toBeDefined();
});