Circular Dependencies and forwardRef

OrdersService needs PaymentsService to charge the customer, and PaymentsService needs OrdersService to mark the order paid. NestJS cannot create either first.

npm run start:dev

[Nest] ERROR [ExceptionHandler] Nest cannot create the OrdersModule instance.
A circular dependency between modules. Use forwardRef() to avoid it.
Scope [AppModule -> OrdersModule -> PaymentsModule]

Wrap the reference in forwardRef() on both sides (module imports and constructor injection):

// orders.module.ts
@Module({ imports: [forwardRef(() => PaymentsModule)], providers: [OrdersService], exports: [OrdersService] })
export class OrdersModule {}

// payments.module.ts
@Module({ imports: [forwardRef(() => OrdersModule)], providers: [PaymentsService], exports: [PaymentsService] })
export class PaymentsModule {}

// orders.service.ts
@Injectable()
export class OrdersService {
  constructor(@Inject(forwardRef(() => PaymentsService)) private readonly payments: PaymentsService) {}
}