NestJS Error Handling Standards

Priority: P1 (OPERATIONAL)

Global error handling and exception management patterns.

• Requirement: Centralize error formatting.
• Platform Agnostic: Do not import Request/Response from Express/Fastify types directly.
• Use: HttpAdapterHost to access the underlying platform response methods.
• const { httpAdapter } = this.httpAdapterHost;
• Structure:
• Implement strictly typed error responses.
• Refer to API Standards for ApiErrorResponse.

json { "statusCode": 400, "message": "Validation failed", "error": "Bad Request", "timestamp": "ISO...", "path": "/users" }

Error Flow

1. Service: Throws specific or generic errors (e.g., EntityNotFoundError).
2. Interceptor: Maps low-level errors to HTTP Exceptions (e.g., catchError(err => throw new NotFoundException())). - Why: Keeps Exception Filters focused on formatting, not business logic interpretation.
3. Global Filter: Formats the final JSON response.

Built-in Exceptions

• Use: Throw NotFoundException, ForbiddenException, BadRequestException.
• Custom: Extend HttpException only for domain-specific failures that need specific status codes.

Logging

• Context: Always pass MyClass.name to the Logger constructor.
• Levels:
• error: 500s (Stack trace required).
• warn: 400s (Client errors).

Security (Information Leakage)

• Production: NEVER expose stack traces in HTTP responses (process.env.NODE_ENV === 'production').
• Sanitization: Ensure ApiException payloads do not leak internal file paths or raw variable dumps.