Structure exception handling patterns

Implement consistent exception handling using framework-provided mechanisms rather than ad-hoc try-catch blocks or manual error propagation. Use appropriate exception classes and interceptors to handle errors at the right architectural level.

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Prompt

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Implement consistent exception handling using framework-provided mechanisms rather than ad-hoc try-catch blocks or manual error propagation. Use appropriate exception classes and interceptors to handle errors at the right architectural level.

Key guidelines:

  1. Use built-in exception classes with proper status codes
  2. Leverage exception interceptors for cross-cutting error handling
  3. Avoid mixing different error handling approaches

Example - INCORRECT approach:

@Controller('cats')
export class CatsController {
  @Post()
  async create(@Body() createCatDto: CreateCatDto) {
    try {
      await this.catsService.create(createCatDto);
    } catch(error) {
      console.error(error);
      return []; // Swallowing error, returning empty result
    }
  }
}

CORRECT approach:

@Controller('cats')
export class CatsController {
  @Post()
  async create(@Body() createCatDto: CreateCatDto) {
    // Let exception filter handle errors
    return await this.catsService.create(createCatDto);
  }
}

// In a custom exception filter
@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) {
    // Proper error handling with status codes and logging
    const status = exception instanceof HttpException 
      ? exception.getStatus()
      : HttpStatus.INTERNAL_SERVER_ERROR;
    // Handle error appropriately...
  }
}

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