NestJS跨仓库模块依赖解析失败问题及解决（npm link相关）

问题场景 #

构建用于私有仓库复用的NestJS模块，经nest build构建后通过npm link关联到主项目时，出现TypeOrm依赖解析错误。模块放在主项目内部时可正常运行，跨仓库引入则触发报错。

错误信息 #

首次报错：

ERROR [ExceptionHandler] Nest can't resolve dependencies of the UserRepository (?). Please make sure that the argument DataSource at index [0] is available in the TypeOrmModule context.

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

尝试在AppModule的providers中添加UsersService后，出现新错误：

ERROR [ExceptionHandler] Nest can't resolve dependencies of the UsersService (?). Please make sure that the argument UserRepository at index [0] is available in the AppModule context.

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

解决方案 #

问题根源是npm link导致数据库连接无法在主项目与私有模块间共享，改用yalc进行包关联后，问题解决。

相关代码 #

AppModule #

import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { UsersModule, User } from '@MY-PACKAGE-LINKED/user';

@Module({
  imports: [
    TypeOrmModule.forRootAsync({
      useFactory: () => ({
        type: 'mysql',
        host: 'localhost',
        port: 3306,
        username: 'root',
        password: 'root',
        database: 'test',
        entities: [User],
        synchronize: true,
      }),
    }),
    UsersModule,
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule { }

UsersModule #

import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { User } from './entities/user.entity';
import { UserRepository } from './users.repository';
@Module({
  imports: [TypeOrmModule.forFeature([User])],
  controllers: [UsersController],
  providers: [UserRepository, UsersService],
})
export class UsersModule { }

UsersService #

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { User } from './entities/user.entity';
import { CreateUserParams } from './utils/types/types';

@Injectable()
export class UsersService {
    constructor(@InjectRepository(User) private userRepository: Repository<User>) { }

    async findOne(username: string): Promise<User | undefined> {
        return this.userRepository.findOne({ where: { username } });
    }

    async findAll(): Promise<User[]> {
        return this.userRepository.find();
    }

    createUser(userDetails: CreateUserParams) {
        const newUser = this.userRepository.create({ ...userDetails, createdAt: new Date() });
        return this.userRepository.save(newUser);
    }
}

内容的提问来源于stack exchange，提问作者ChristmasFighters