NestJS中使用Mongoose连接MongoDB遇undefined错误求助

问题场景 #

开发NestJS应用连接MongoDB时，按照官方文档配置Mongoose并使用mongoose-unique-validator等插件，模块代码及依赖配置如下，但始终报错：'First param to schema.plugin() must be a function, got "undefined"'

模块代码 #

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,
      envFilePath: `.env.${process.env.NODE_ENV}`,
    }),
    MongooseModule.forRootAsync({
      useFactory: async (configService: ConfigService) => ({
        uri: configService.get<string>('MONGO_URI'),
        autoIndex: true,
        useNewUrlParser: true,
        useUnifiedTopology: true,
        connectionFactory: (connection: MongooseConnection) => {
          // Global plugins
          connection.plugin(mongooseUniqueValidator);
          connection.plugin(mongoosePaginate);
          connection.plugin(mongooseToJson);
          return connection;
        },
      }),
      inject: [ConfigService],
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})

package.json依赖 #

"dependencies": {
    "@nestjs/common": "^9.0.0",
    "@nestjs/config": "^2.2.0",
    "@nestjs/core": "^9.0.0",
    "@nestjs/mapped-types": "*",
    "@nestjs/mongoose": "^9.1.1",
    "@nestjs/platform-express": "^9.0.0",
    "@nestjs/platform-socket.io": "^9.2.1",
    "@nestjs/websockets": "^9.2.1",
    "helmet": "^6.0.1",
    "mongoose": "^6.4.3",
    "mongoose-paginate-v2": "^1.7.1",
    "mongoose-unique-validator": "^2.0.3",
    "openai": "^3.1.0",
    "reflect-metadata": "^0.1.13",
    "rimraf": "^3.0.2",
    "rxjs": "^7.2.0"
  },

解决建议 #

1. 检查插件导入是否正确 #

报错核心原因是传入connection.plugin()的插件不是函数（即变量为undefined），大概率是导入方式错误：
确认所有插件的导入语句符合包的导出规则，示例：

// 正确导入mongoose-unique-validator（默认导出）
import mongooseUniqueValidator from 'mongoose-unique-validator';
// 正确导入mongoose-paginate-v2（默认导出）
import mongoosePaginate from 'mongoose-paginate-v2';

2. 补充缺失的插件依赖 #

代码中使用了mongooseToJson但package.json未包含对应依赖，需先安装常用的适配包：

npm install @meanie/mongoose-to-json

然后正确导入：

import mongooseToJson from '@meanie/mongoose-to-json';

3. 验证版本兼容性并重新安装依赖 #

当前mongoose@6.4.3与已安装的插件版本兼容，但如果存在隐性冲突，可尝试重置依赖：

rm -rf node_modules package-lock.json
npm install

4. 切换到Schema级别注册插件（备选方案） #

如果全局注册仍有问题，可改为在具体Schema中单独注册，示例：

import { Schema } from 'mongoose';
import mongooseUniqueValidator from 'mongoose-unique-validator';

const UserSchema = new Schema({
  email: { type: String, unique: true }
});
UserSchema.plugin(mongooseUniqueValidator);

内容的提问来源于stack exchange，提问作者khoi vu