KnowledgeBase/docs/DEVELOPMENT_STANDARDS.md

Development Standards

Code Language Requirements

1. Comments

• All code comments must be in English
• Includes the following (not limited to):
  • Function/method comments
  • Inline comments
  • Code block explanations
  • TODO/FIXME comments

2. Logging

• All log output must be in English
• Includes the following (not limited to):
  • logger.log() info logs
  • logger.warn() warning logs
  • logger.error() error logs
  • console.log() debug output

3. Error Messages

• Error messages must support internationalization (i18n)
• User-facing error messages: Display in the user's selected language (Japanese/Chinese/English) via i18n system
• Debug/development error messages: Display in the user's selected language via i18n system
• Exception messages: Use i18n for internationalized error messages

Examples

Correct Comments and Logs (English + i18n)

// Get embeddings for texts
async getEmbeddings(texts: string[]): Promise<number[][]> {
  this.logger.log(`Getting embeddings for ${texts.length} texts`);
  
  try {
    // Call API to get embeddings
    const response = await this.callEmbeddingAPI(texts);
    return response.data;
  } catch (error) {
    this.logger.error('Failed to get embeddings', error);
    // Use i18n for user-facing error messages
    throw new Error(this.i18n.t('errors.embeddingGenerationFailed'));
  }
}

Using i18n for Error Messages

import { I18nService } from './i18n.service';

async processDocument(file: Express.Multer.File) {
  try {
    // Process document...
    return result;
  } catch (error) {
    // Error message in user's selected language
    throw new Error(this.i18n.t('errors.documentProcessingFailed', {
      filename: file.originalname
    }));
  }
}

Compliance Standards

1. During code reviews, always check the language of comments and logs
2. New code must follow English comments and logs standards
3. When refactoring existing code, update comments and logs to English simultaneously
4. All error messages must use the i18n system for internationalization

Validation i18n Rules

class-validator Limitation

The @MinLength, @MaxLength, @IsEmail, etc. decorators from class-validator have a static message property that cannot access NestJS's I18nService at runtime. Therefore:

• DO NOT use hardcoded messages in validation decorators like:

  @MinLength(8, { message: 'Password must be at least 8 characters long' })
  

• DO perform validation in the controller layer with i18n support:

  if (password.length < 6) {
  throw new BadRequestException(this.i18nService.getErrorMessage('passwordMinLength'));
  }
  

• OR remove the decorator and rely on controller-level validation only

Adding New Validation Rules

When adding new validation to DTOs, ensure validation messages are internationalized by:

1. Adding the i18n key to server/src/i18n/messages.ts
2. Adding validation logic in the controller or service layer using I18nService