NestJs/Mongoose自增序列因类型检查失败，求解决方案

问题分析 #

报错根源是@types/mongoose-sequence的类型定义存在错误：

1. 错误将AutoIncrementFactory的参数类型限定为Schema，但实际该工厂函数支持传入mongoose实例或Connection对象
2. 错误标记工厂函数返回值为void，但实际应返回mongoose插件函数

以下是三种保留类型检查的解决方案：

方案1：传入mongoose实例（推荐） #

直接导入mongoose模块实例传给工厂函数，完全符合类型预期：

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { UserController } from './user.controller';
import { UserService } from './user.service';
import { User, UserSchema } from './schema/user.schema';
import * as AutoIncrementFactory from 'mongoose-sequence';
import mongoose from 'mongoose';

@Module({
  imports: [
    MongooseModule.forFeatureAsync([
      {
        name: User.name,
        useFactory: async () => {
          const schema = UserSchema;
          const AutoIncrement = AutoIncrementFactory(mongoose);
          schema.plugin(AutoIncrement, { inc_field: 'users' });
          return schema;
        },
      },
    ]),
  ],
  controllers: [UserController],
  providers: [UserService],
  exports: [UserService],
})
export class UserModule {}

方案2：类型断言绕过错误检查 #

如果必须使用注入的Connection，通过类型断言跳过错误的类型校验，同时保留其他代码的类型检查：

import { Module } from '@nestjs/common';
import { MongooseModule, getConnectionToken } from '@nestjs/mongoose';
import { UserController } from './user.controller';
import { UserService } from './user.service';
import { User, UserSchema } from './schema/user.schema';
import * as AutoIncrementFactory from 'mongoose-sequence';
import { Connection, PluginFunction } from 'mongoose';

@Module({
  imports: [
    MongooseModule.forFeatureAsync([
      {
        name: User.name,
        useFactory: async (connection: Connection) => {
          const schema = UserSchema;
          // 用类型断言修正参数和返回值类型
          const AutoIncrement = AutoIncrementFactory(connection as any) as PluginFunction<User>;
          schema.plugin(AutoIncrement, { inc_field: 'users' });
          return schema;
        },
        inject: [getConnectionToken()],
      },
    ]),
  ],
  controllers: [UserController],
  providers: [UserService],
  exports: [UserService],
})
export class UserModule {}

方案3：自定义类型声明修复根源 #

在项目中添加自定义类型声明文件src/types/mongoose-sequence.d.ts，覆盖错误的官方类型定义：

declare module 'mongoose-sequence' {
  import mongoose, { Connection, PluginFunction } from 'mongoose';

  type AutoIncrementFactory = (mongooseOrConnection: typeof mongoose | Connection) => PluginFunction<any>;

  const factory: AutoIncrementFactory;
  export = factory;
}

添加后，你的原代码无需任何修改即可通过TypeScript类型检查。

内容的提问来源于stack exchange，提问作者cityvoice