@osskit/fastify-error-handler

@osskit/fastify-error-handler is a reusable error handler for Fastify. It helps you manage error responses in a consistent and customizable manner, with built-in support for logging and filtering allowed error properties.

Features

Handles various error types and provides appropriate HTTP status codes.
Logs errors with customizable logging function.
Allows specifying which properties of the error object should be included in the response.
Works seamlessly with Fastify's error handling mechanism.

Installation

Install the package via npm:

npm install @osskit/fastify-error-handler

Or via yarn:

yarn add @osskit/fastify-error-handler

Usage

Basic Usage

import fastify from 'fastify';
import { fastifyErrorHandler } from '@osskit/fastify-error-handler';

const server = fastify();

server.setErrorHandler(fastifyErrorHandler());

server.get('/', async () => {
  // Simulate an error
  throw new Error('Test error');
});

server.listen(3000, (err, address) => {
  if (err) {
    console.error(err);
    process.exit(1);
  }
  console.log(`Server listening at ${address}`);
});

Custom Logging and Allowed Properties

You can customize the error handler by providing a logging function and specifying which properties of the error object should be included in the response.

import fastify from 'fastify';
import { fastifyErrorHandler } from '@osskit/fastify-error-handler';

const server = fastify();

const customLogger = ({ error, request, reply }) => {
  console.log('Custom log:', error);
};

const options = {
  log: customLogger,
  allowedProperties: ['detail', 'type']
};

server.setErrorHandler(fastifyErrorHandler(options));

server.get('/', async () => {
  const error = new Error('Test error');
  error.detail = 'Detailed error information';
  error.type = 'CustomError';
  throw error;
});

server.listen(3000, (err, address) => {
  if (err) {
    console.error(err);
    process.exit(1);
  }
  console.log(`Server listening at ${address}`);
});

Handling HTTP Errors

The error handler works well with HTTP errors created using libraries like http-errors.

import fastify from 'fastify';
import createHttpError from 'http-errors';
import { fastifyErrorHandler } from '@osskit/fastify-error-handler';

const server = fastify();

server.setErrorHandler(fastifyErrorHandler());

server.get('/not-found', async () => {
  throw createHttpError(404, 'Resource not found');
});

server.listen(3000, (err, address) => {
  if (err) {
    console.error(err);
    process.exit(1);
  }
  console.log(`Server listening at ${address}`);
});

API

fastifyErrorHandler(options?)

Returns a Fastify error handler function.

options

log (optional): A function to log errors. Receives an object with error, request, and reply properties.
allowedProperties (optional): An iterable of property names that are allowed to be included in the error response.

License

This package is licensed under the MIT License. See the LICENSE file for more details.