Restful Error Responses

// Standard error response structure
{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "The request body contains invalid fields.",
    "details": [
      {
        "field": "email",
        "message": "Must be a valid email address",
        "code": "INVALID_FORMAT"
      },
      {
        "field": "age",
        "message": "Must be a positive integer",
        "code": "INVALID_VALUE"
      }
    ],
    "request_id": "req-abc123",
    "documentation_url": "https://docs.example.com/errors#VALIDATION_ERROR"
  }
}

class APIException(Exception):
    def __init__(self, status_code, code, message, details=None):
        self.status_code = status_code
        self.code = code
        self.message = message
        self.details = details or []

@app.errorhandler(APIException)
def handle_api_error(error):
    response = jsonify({
        "error": {
            "code": error.code,
            "message": error.message,
            "details": error.details,
            "request_id": getattr(request, 'request_id', ''),
            "documentation_url": f"https://docs.example.com/errors#{error.code}"
        }
    })
    response.status_code = error.status_code
    return response

@app.route('/users', methods=['POST'])
def create_user():
    data = request.json
    errors = []

    if not data.get('name'):
        errors.append({
            "field": "name",
            "message": "Name is required",
            "code": "REQUIRED"
        })

    if data.get('email') and '@' not in data['email']:
        errors.append({
            "field": "email",
            "message": "Must be a valid email address",
            "code": "INVALID_FORMAT"
        })

    if errors:
        raise APIException(422, 'VALIDATION_ERROR',
                          'The request body contains invalid fields.', errors)

    user = db.create_user(data)
    return jsonify(user.to_dict()), 201

// Express error handler
class APIError extends Error {
  constructor(statusCode, code, message, details = []) {
    super(message);
    this.statusCode = statusCode;
    this.code = code;
    this.details = details;
  }
}

function errorHandler(err, req, res, next) {
  const status = err.statusCode || 500;
  const response = {
    error: {
      code: err.code || 'INTERNAL_ERROR',
      message: err.message || 'An unexpected error occurred',
      details: err.details || [],
      request_id: req.requestId
    }
  };

  res.status(status).json(response);
}

app.use(errorHandler);