problem nestjs - Nest can't resolve dependencies of the AuthenticationService (?)

Question

The application stops immediately at startup, other modules have not been checked yet, so the error is unlikely in them.

authentication.service.ts

import { HttpException, HttpStatus, Inject, Injectable } from '@nestjs/common';
import { CreateUserDto } from 'src/users/dto/createUser.dto';
import { UserService } from 'src/users/user/user.service';
import bcrypt from 'bcrypt';

@Injectable()
export class AuthenticationService {
    constructor(@Inject() private readonly userService: UserService){}
    public async regiser(registartionData:CreateUserDto){
    const hashingPassword = await bcrypt.hash(registartionData.passwordHash, 10);
    try{
        const createUser = await this.userService.create({
            ...registartionData,
            passwordHash: hashingPassword
        })
        createUser.passwordHash = undefined;
        return createUser;
    }
    catch(err){
        throw new HttpException('Something went wrong', HttpStatus.INTERNAL_SERVER_ERROR);
    }
}
public async getAuthenticationUser(email:string, textPassword:string){
    try{
        const user = await this.userService.findByEmail(email);
        await this.verifyPassword(textPassword,user.passwordHash);
        user.passwordHash = undefined;
        return user;
    }
    catch(err){
        throw new HttpException('Wrong credentials provided', HttpStatus.BAD_REQUEST);
    }
}
private async verifyPassword(password:string, hashingPassword:string){
    const isMatching = await bcrypt.compare(password, hashingPassword);
    if(!isMatching) throw new HttpException('Wrong credentials provided', HttpStatus.BAD_REQUEST);
}
}

auth.module.ts

import { Module } from '@nestjs/common';
import { PassportModule } from '@nestjs/passport';
import { UsersModule } from 'src/users/users.module';
import { AuthController } from '../controllers/auth/auth.controller';
import { AuthenticationService } from './authentication/authentication.service';
import { LocalStrategy } from './authentication/local.strategy';

@Module({
  imports:[UsersModule, PassportModule, ],
  providers: [AuthenticationService, LocalStrategy],
  controllers:[AuthController],
  exports: [AuthenticationService]
})
export class AuthModule {}

this error

 Nest can't resolve dependencies of the AuthenticationService (?). Please make sure that the argument dependency at index [0] is available in the AuthModule context.

Potential solutions:
- If dependency is a provider, is it part of the current AuthModule?
- If dependency is exported from a separate @Module, is that module imported within AuthModule?
  @Module({
    imports: [ /* the Module containing dependency */ ]
  })

I don't understand error, export and provide auth service. I don't use auth service in other modules.

Answer 1

All my services use the mongodb model. Therefore, you need to do the following in modules and services.

user.module.ts

@Module({
*imports: [MongooseModule.forFeature([{ name: 'User', schema: UserSchema }])],*
  providers: [UserService],
  exports: [UserService],
})
export class UsersModule {}

user.service.ts

@Injectable()
export class UserService implements IUserService {
  constructor(
*@InjectModel(User.name) private userModel: Model<User>*
) {}

good example https://wanago.io/2021/08/23/api-nestjs-relationships-mongodb/

Answer 2

The code in yours repo cannot be even compiled, so cannot help you almost at all. There are lack of things, ts-errors etc.

but from what i see:

• UsersModule has provider UserService but its not exporting it. Therefore NO OTHER MODULE would have access to it. You need to export the UserService too.
• AuthModule do not imports UserService (and nothing exports it) so its not found at the time of Nest trying to match injects. What you can do is to add imports: [UserModule] in AuthModule (and also export UserService in UserModule).

And read again the documentation of modules and example project to see how imports, exports, controllers and providers works.