slack-error.js

const ErrorStackParser = require('error-stack-parser')
const Slack = require('slack-node')

const config = require('../config')
const packageJson = require('../../package.json')

const slack = new Slack()
slack.setWebhook(config.slackHookUrl)

module.exports = (err, req, res, next) => {
  // I don't want to send notifications for catched errors
  // such as HTTP 400, 401, 404 errors. These errors
  // created with npm http-errors have a `statusCode` attribute.
  if (err.statusCode) return next(err)

  // I don't want to raise errors on slack when I am
  // working on my local environment
  if (!config.slackHookUrl) return next(err)
  
  // This is optionnal but convenient to get a
  // github link to the code line that raised the error
  const sourceLink = getSourceLink(err)

  slack.webhook({
    channel: config.errorChannel,
    username: 'lalibot',
    attachments: [
      {
        fallback: 'An uncaught error occured',
        color: '#f67258',
        title: 'An uncaught error occured on the Express API',
        text: err.message + (sourceLink ? ` ${sourceLink}` : '')
      }
    ]
  }, (err) => {
    // an error occurred when sending an error 🙄
    logger.error(err.message)
  })

  return next(err)
}

const getSourceLink = (error) => {
  if (!packageJson.repository || !packageJson.repository.url) return null
  const branch = process.env.NODE_ENV === 'production' ? 'master' : 'staging'

  const stack = ErrorStackParser.parse(error)

  if (Array.isArray(stack)) {
    // I can provide a link to source code only if it
    // comes from our code. Not from node modules.
    const stackItemsFromSrc = stack.filter((item) => item.fileName.match(/(src\/.*)$/))
    if (stackItemsFromSrc.length > 0) {
      const match = stackItemsFromSrc[0].fileName.match(/(src\/.*)$/)
      if (match) {
        return `<${packageJson.repository.url}/blob/${branch}/${match[1]}#L${stack[0].lineNumber}|See on Github>`
      }
    }
  }
  return null
}