在NestJS/TypeORM中检测重复值异常时code属性的TS类型

场景背景 #

我使用NestJS搭配TypeORM和Postgres数据库，已经为实体的username字段设置了唯一约束，实体代码如下：

@Entity()
export class DataEntity {
  @PrimaryGeneratedColumn('uuid')
  id: string;

  @Column({ unique: true })
  username: string;
  
  // 其他属性...
}

当前实现问题 #

向数据库添加数据时，需要在检测到重复username时返回错误提示。目前将catch中的ex设为any类型时代码可正常运行，但希望使用正确的TypeScript强类型。ex.code属性确实存在，但找不到包含该属性的对应类型。理想写法是if (ex instanceof WhateverError && ex.code === '23505')，但不清楚对应的错误类型。当前服务代码如下：

async createThing(data: dataDto): Promise<DataEntity> {

  try {
    // 数据库操作...
  } catch (ex) {
    console.log(ex);
    if (ex.code === '23505') {
      // 23505是Postgres检测到唯一约束冲突的错误码
      this.logger.error(`Username '${username}' already exists!`);
      throw new ConflictException(`Username '${username}' already exists!`);
    } else {
      this.logger.error(`Failed to create data! Data: ${JSON.stringify(createOrgDto)}`);
      throw new InternalServerErrorException();
    }
  }
}

错误日志详情 #

控制台输出的错误信息（已修改部分敏感内容）：

QueryFailedError: duplicate key value violates unique constraint "UQ_e288cba8a890c81abc9dbac6b33"
    at PostgresQueryRunner.query (C:\Users\chris\myproj\src\driver\postgres\PostgresQueryRunner.ts:299:19)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at InsertQueryBuilder.execute (C:\Users\chris\myproj\src\query-builder\InsertQueryBuilder.ts:163:33)
    at SubjectExecutor.executeInsertOperations (C:\Users\chris\myproj\src\persistence\SubjectExecutor.ts:434:42)
    at SubjectExecutor.execute (C:\Users\chris\myproj\src\persistence\SubjectExecutor.ts:137:9)
    at EntityPersistExecutor.execute (C:\Users\chris\myproj\src\persistence\EntityPersistExecutor.ts:182:21)
    at DataService.createData (C:\Users\chris\myproj\src\data\data.service.ts:43:7) {
  query: 'INSERT INTO "Data"("id", "username", "password", "name", "logoUrl", "type", "superAdmin") VALUES (DEFAULT, $1, $2, $3, DEFAULT, DEFAULT, DEFAULT) RETURNING "id", "logoUrl", "type", "superAdmin"',
  parameters: [
    'foo',
    '<REDACTED_PASSWORD>',
    'FooCorp'
  ],
  driverError: error: duplicate key value violates unique constraint "UQ_e288cba8a890c81abc9dbac6b33"
      at C:\Users\chris\myproj\node_modules\pg\lib\client.js:526:17
      at processTicksAndRejections (node:internal/process/task_queues:95:5)
      at PostgresQueryRunner.query (C:\Users\chris\myproj\src\driver\postgres\PostgresQueryRunner.ts:249:25)
      at InsertQueryBuilder.execute (C:\Users\chris\myproj\src\query-builder\InsertQueryBuilder.ts:163:33)
      at SubjectExecutor.executeInsertOperations (C:\Users\chris\myproj\src\persistence\SubjectExecutor.ts:434:42)
      at SubjectExecutor.execute (C:\Users\chris\myproj\src\persistence\SubjectExecutor.ts:137:9)
      at EntityPersistExecutor.execute (C:\Users\chris\myproj\src\persistence\EntityPersistExecutor.ts:182:21)
      at DataService.createData (C:\Users\chris\myproj\src\data\data.service.ts:43:7) {
    length: 249,
    severity: 'ERROR',
    code: '23505',
    detail: 'Key (username)=(foo) already exists.',
    hint: undefined,
    position: undefined,
    internalPosition: undefined,
    internalQuery: undefined,
    where: undefined,
    schema: 'public',
    table: 'Data',
    column: undefined,
    dataType: undefined,
    constraint: 'UQ_e288cba8a890c81abc9dbac6b33',
    file: 'nbtinsert.c',
    line: '666',
    routine: '_bt_check_unique'
  },
  length: 249,
  severity: 'ERROR',
  code: '23505',
  detail: 'Key (username)=(foo) already exists.',
  hint: undefined,
  position: undefined,
  internalPosition: undefined,
  internalQuery: undefined,
  where: undefined,
  schema: 'public',
  table: 'Data',
  column: undefined,
  dataType: undefined,
  constraint: 'UQ_e288cba8a890c81abc9dbac6b33',
  file: 'nbtinsert.c',
  line: '666',
  routine: '_bt_check_unique'
}

疑问 #

我已经尝试使用QueryFailedError类型，但它并没有code属性。难道只能强制使用any类型吗？

解决方案 #

1. 自定义类型守卫实现强类型判断 #

TypeORM的QueryFailedError本身未暴露code属性，但它包含的driverError字段是Postgres驱动抛出的错误对象，自带code属性。可以通过自定义类型守卫来实现强类型校验：

import { QueryFailedError } from 'typeorm';
import { PostgresError } from 'pg';

// 判断是否为Postgres唯一约束冲突错误
function isUniqueConstraintError(error: unknown): error is QueryFailedError & { driverError: PostgresError } {
  return (
    error instanceof QueryFailedError &&
    typeof (error as any).driverError === 'object' &&
    (error as any).driverError.code === '23505'
  );
}

在catch块中使用该守卫：

async createThing(data: dataDto): Promise<DataEntity> {
  try {
    // 执行数据库操作
    return await this.dataRepository.save(data);
  } catch (ex) {
    if (isUniqueConstraintError(ex)) {
      this.logger.error(`Username '${data.username}' already exists!`);
      throw new ConflictException(`Username '${data.username}' already exists!`);
    } else {
      this.logger.error(`Failed to create data! Data: ${JSON.stringify(data)}`);
      throw new InternalServerErrorException();
    }
  }
}

2. 扩展TypeORM的QueryFailedError类型声明 #

如果不想写类型守卫，可以通过扩展模块类型的方式，给QueryFailedError添加code属性的类型定义。在项目中新建typeorm.d.ts文件：

import { QueryFailedError } from 'typeorm';

declare module 'typeorm' {
  interface QueryFailedError {
    code: string;
    driverError: {
      code: string;
      detail: string;
      // 可按需添加其他需要的属性
    };
  }
}

添加后TypeScript会自动识别QueryFailedError上的code属性，无需额外类型转换。

3. 直接结合pg库的错误类型判断 #

Postgres驱动的错误类型在pg包的PostgresError中，可以直接结合它进行判断：

import { QueryFailedError } from 'typeorm';
import { PostgresError } from 'pg';

// 在catch块中
async createThing(data: dataDto): Promise<DataEntity> {
  try {
    // 数据库操作
  } catch (ex) {
    if (ex instanceof QueryFailedError && (ex.driverError as PostgresError).code === '23505') {
      this.logger.error(`Username '${data.username}' already exists!`);
      throw new ConflictException(`Username '${data.username}' already exists!`);
    } else {
      // 其他错误处理
      throw new InternalServerErrorException();
    }
  }
}

内容的提问来源于stack exchange，提问作者Chris Barr