express-async-errors.js

// Original work Copyright (c) 2016, Nikolay Nemshilov <nemshilov@gmail.com>
// Modified work Copyright (c) 2016, David Banham <david@banham.id.au>
//
// Permission to use, copy, modify, and/or distribute this software for any purpose
// with or without fee is hereby granted, provided that the above copyright notice
// and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
// OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
// TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
// THIS SOFTWARE.

// Originally taken from https://raw.githubusercontent.com/davidbanham/express-async-errors/master/index.js
// Express versions before v5 does not support promises and as such do not properly handle the errors in
// async routes. This code patches Express to fix that.

const Layer = require('express/lib/router/layer');
const Router = require('express/lib/router');

const last = (arr = []) => arr[arr.length - 1];
const noop = Function.prototype;

function copyFnProps(oldFn, newFn) {
  Object.keys(oldFn).forEach((key) => {
    newFn[key] = oldFn[key];
  });
  return newFn;
}

function wrap(fn) {
  const newFn = function newFn(...args) {
    const ret = fn.apply(this, args);
    const next = (args.length === 5 ? args[2] : last(args)) || noop;
    if (ret && ret.catch) ret.catch(err => next(err));
    return ret;
  };
  Object.defineProperty(newFn, 'length', {
    value: fn.length,
    writable: false,
  });
  return copyFnProps(fn, newFn);
}

function patchRouterParam() {
  const originalParam = Router.prototype.constructor.param;
  Router.prototype.constructor.param = function param(name, fn) {
    fn = wrap(fn);
    return originalParam.call(this, name, fn);
  };
}

Object.defineProperty(Layer.prototype, 'handle', {
  enumerable: true,
  get() {
    return this.__handle;
  },
  set(fn) {
    fn = wrap(fn);
    this.__handle = fn;
  },
});

patchRouterParam();