Function handleError

middleware/handle-errors.js:31–96

(error, req, res, next)

}

export default async function handleError(error, req, res, next) {
  const responseDone = res.headersSent || req.aborted

  if (req.path.startsWith('/assets') || req.path.startsWith('/_next/static')) {
    if (!responseDone) {
      // By default, Fastly will cache 404 responses unless otherwise
      // told not to.
      // See https://docs.fastly.com/en/guides/how-caching-and-cdns-work#http-status-codes-cached-by-default
      // Let's cache our 404'ing assets conservatively.
      // The Cache-Control is short, and let's use the default surrogate
      // key just in case it was a mistake.
      errorCacheControl(res)
      // Makes sure the surrogate key is NOT the manual one if it failed.
      // This basically unsets what was assumed in the beginning of
      // loading all the middlewares.
      setFastlySurrogateKey(res, SURROGATE_ENUMS.DEFAULT)
    }
  } else if (DEBUG_MIDDLEWARE_TESTS) {
    console.warn('An error occurrred in some middleware handler', error)
  }

  try {
    // If the headers have already been sent or the request was aborted...
    if (responseDone) {
      // Report to Failbot
      await logException(error, req)

      // We MUST delegate to the default Express error handler
      return next(error)
    }

    if (!req.context) {
      req.context = {}
    }
    // display error on the page in development and staging, but not in production
    if (process.env.HEROKU_PRODUCTION_APP !== 'true') {
      req.context.error = error
    }

    // Special handling for when a middleware calls `next(404)`
    if (error === 404) {
      // Note that if this fails, it will swallow that error.
      return nextApp.render404(req, res)
    }

    // If the error contains a status code, just send that back. This is usually
    // from a middleware like `express.json()`.
    if (error.statusCode || error.status) {
      return res.sendStatus(error.statusCode || error.status)
    }

    if (process.env.NODE_ENV !== 'test') {
      console.error('500 error!', req.path)
      console.error(error)
    }

    res.statusCode = 500
    nextApp.renderError(error, req, res, req.path)