@khoativi/nestjs-class-validator-i18n

@khoativi/nestjs-class-validator-i18n is a lightweight NestJS extension to provide localized error messages for class-validator without needing to customize each decorator. It supports multi-language validation errors via standard JSON files and integrates with ValidationPipe and ExceptionFilter.

✨ Key Features

• 🌍 Supports multiple languages (e.g., en, vi)
• 📥 Reads Accept-Language header to determine language dynamically
• 📦 Plug-and-play integration with NestJS's ValidationPipe
• 🧩 Customizable message files for each locale
• ⚡ Zero config needed per-decorator

📦 Installation

npm:

npm install @khoativi/nestjs-class-validator-i18n

yarn:

yarn add @khoativi/nestjs-class-validator-i18n

pnpm:

pnpm add @khoativi/nestjs-class-validator-i18n

🚀 Usage

1. Register Global Pipes and Filter

Use the provided exception and filter classes to apply localized validation globally.

// main.ts
import {
  I18nValidationException,
  I18nValidationFilter,
} from '@khoativi/nestjs-class-validator-i18n';
import { ValidationPipe } from '@nestjs/common';
import { HttpAdapterHost, NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  app.useGlobalPipes(
    new ValidationPipe({
      whitelist: true,
      transform: true,
      forbidNonWhitelisted: true,
      exceptionFactory: (errors) => new I18nValidationException(errors),
    }),
  );

  const adapterHost = app.get(HttpAdapterHost);
  app.useGlobalFilters(
    new I18nValidationFilter(adapterHost, { fallbackLanguage: 'vi' }),
  );

  await app.listen(3000);
}

bootstrap();

2. Create DTO with class-validator

import { IsEmail, IsNotEmpty } from 'class-validator';

export class CreateUserDto {
  @IsEmail()
  email: string;

  @IsNotEmpty()
  name: string;
}

3. Send a request with Accept-Language header

POST /users
Accept-Language: vi
Content-Type: application/json

{
  "email": "not-an-email"
}

Response:

{
  "statusCode": 400,
  "message": "email phải là email hợp lệ",
  "error": "Bad Request"
}

🛠️ Issues and Contributing

Feel free to open issues or submit pull requests for improvements, bug fixes, or additional language support.

📄 License

MIT License © Khoa Trần