index.js

/*!
 * errorhandler
 * Copyright(c) 2010 Sencha Inc.
 * Copyright(c) 2011 TJ Holowaychuk
 * Copyright(c) 2014 Jonathan Ong
 * MIT Licensed
 */

/**
 * Module dependencies.
 */

var accepts = require('accepts')
var escapeHtml = require('escape-html');
var fs = require('fs');
var util = require('util')

/**
 * Module variables.
 */

var inspect = util.inspect
var toString = Object.prototype.toString

/**
 * Error handler:
 *
 * Development error handler, providing stack traces
 * and error message responses for requests accepting text, html,
 * or json.
 *
 * Text:
 *
 *   By default, and when _text/plain_ is accepted a simple stack trace
 *   or error message will be returned.
 *
 * JSON:
 *
 *   When _application/json_ is accepted, connect will respond with
 *   an object in the form of `{ "error": error }`.
 *
 * HTML:
 *
 *   When accepted connect will output a nice html stack trace.
 *
 * @return {Function}
 * @api public
 */

exports = module.exports = function errorHandler(){
  // get environment
  var env = process.env.NODE_ENV || 'development'

  return function errorHandler(err, req, res, next){
    // respect err.status
    if (err.status) {
      res.statusCode = err.status
    }

    // default status code to 500
    if (res.statusCode < 400) {
      res.statusCode = 500
    }

    // write error to console
    if (env !== 'test') {
      console.error(stringify(err))
    }

    // cannot actually respond
    if (res._header) {
      return req.socket.destroy()
    }

    // negotiate
    var accept = accepts(req)
    var type = accept.types('html', 'json', 'text')

    // Security header for content sniffing
    res.setHeader('X-Content-Type-Options', 'nosniff')

    // html
    if (type === 'html') {
      fs.readFile(__dirname + '/public/style.css', 'utf8', function(e, style){
        if (e) return next(e);
        fs.readFile(__dirname + '/public/error.html', 'utf8', function(e, html){
          if (e) return next(e);
          var stack = String(err.stack || '')
            .split('\n').slice(1)
            .map(function(v){ return '<li>' + escapeHtml(v).replace(/  /g, ' &nbsp;') + '</li>'; }).join('');
            html = html
              .replace('{style}', style)
              .replace('{stack}', stack)
              .replace('{title}', escapeHtml(exports.title))
              .replace('{statusCode}', res.statusCode)
              .replace(/\{error\}/g, escapeHtml(stringify(err)).replace(/  /g, ' &nbsp;').replace(/\n/g, '<br>'));
            res.setHeader('Content-Type', 'text/html; charset=utf-8');
            res.end(html);
        });
      });
    // json
    } else if (type === 'json') {
      var error = { message: err.message, stack: err.stack };
      for (var prop in err) error[prop] = err[prop];
      var json = JSON.stringify({ error: error });
      res.setHeader('Content-Type', 'application/json');
      res.end(json);
    // plain text
    } else {
      res.setHeader('Content-Type', 'text/plain');
      res.end(stringify(err));
    }
  };
};

/**
 * Template title, framework authors may override this value.
 */

exports.title = 'Connect';

/**
 * Stringify a value.
 * @api private
 */

function stringify(val) {
  var stack = val.stack

  if (stack) {
    return String(stack)
  }

  var str = String(val)

  return str === toString.call(val)
    ? inspect(val)
    : str
}