HTTP Problem Details for express

Based on http-problem-details (repository | npm) and http-problem-details-mapper (repository | npm), this library allows you to map your Node.js errors to HTTP Problem details according to RFC7807 by convention.

Installation

npm install express express-http-problem-details

or

yarn add express express-http-problem-details

Usage

express-http-problem-details provides a middleware which allows you to map custom Error instances to HTTP Problem Details documents according to RFC7807.

The details of the mapping itself are described in http-problem-details-mapper (repository | npm)

Example

The typical workflow in JavaScript/ES2015 with http-problem-details-mapper is this:

First, you implement an Error

class NotFoundError extends Error {
  constructor (options) {
    const { type, id } = options
    super()
    Error.captureStackTrace(this, this.constructor)

    this.message = `${type} with id ${id} could not be found.`
  }
}

Next, you extend the ErrorMapper class:

import { ProblemDocument } from 'http-problem-details'
import { ErrorMapper } from 'http-problem-details-mapper'

class NotFoundErrorMapper extends ErrorMapper {
  constructor() {
    super(NotFoundError)
  }

  mapError (error) {
    return new ProblemDocument({
      status: 404,
      title: error.message,
      type: 'http://tempuri.org/NotFoundError'
    })
  }
}

Finally, create an instance of ExpressMappingStrategy to hold the mappers and register everything in your app. Notice that the HttpProblemResponse must come last. A global error logger would precede it and forward the error to the next function.

import { HttpProblemResponse } from 'express-http-problem-details'
import { DefaultMappingStrategy, MapperRegistry } from 'http-problem-details-mapper'

const strategy = new DefaultMappingStrategy(
    new MapperRegistry()
      .registerMapper(new NotFoundErrorMapper()))


const server = express()

server.get('/', async (req, res) => {
  return res.send(new NotFoundError({type: 'customer', id: '123' }))
})
server.use(function logErrors (err, req, res, next) {
  console.error(err.stack)
  next(err)
})
server.use(HttpProblemResponse({strategy}))

server.listen(3000)

When GETting localhost:3000, the result will be like this:

HTTP/1.1 404 Not Found
Connection: keep-alive
Content-Length: 107
Content-Type: application/problem+json; charset=utf-8
Date: Wed, 24 Apr 2019 23:48:27 GMT
ETag: W/"6b-dSoRnzOA0Ls+QaHyomC8H+uv7GQ"
X-Powered-By: Express

{
    "status": 404,
    "title": "customer with id 123 could not be found.",
    "type": "http://tempuri.org/NotFoundError"
}

When just returning a return res.status(500).send();, you'll get a response like this:

HTTP/1.1 500 Internal Server Error
Connection: keep-alive
Content-Length: 67
Content-Type: application/problem+json; charset=utf-8
Date: Thu, 25 Apr 2019 00:01:48 GMT
ETag: W/"43-U3E8vFCP1+XTg1JqRHkrjQWiN60"
X-Powered-By: Express

{
    "status": 500,
    "title": "Internal Server Error",
    "type": "about:blank"
}

Running the tests

npm test

or

yarn test

Want to help?

This project is just getting off the ground and could use some help with cleaning things up and refactoring.

If you want to contribute - we'd love it! Just open an issue to work against so you get full credit for your fork. You can open the issue first so we can discuss and you can work your fork as we go along.

If you see a bug, please be so kind as to show how it's failing, and we'll do our best to get it fixed quickly.

Before sending a PR, please create an issue to introduce your idea and have a reference for your PR.

We're using conventional commits, so please use it for your commits as well.

Also please add tests and make sure to run npm run lint-ts or yarn lint-ts.

License

MIT License

Copyright (c) 2019 PDMLab

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.