must-have-errors.js

var EE = require('events').EventEmitter;

EE.prototype.emit = (function(orig) {
  return function() {
    if (this.listeners('error').length === 0) {
      console.error(this.constructor.name, this);
      throw new Error('EE without an error listener');
    }
    return orig.apply(this, arguments);
  };
})(EE.prototype.emit);

var http = require('http');

var server = http.createServer(function(req, res) {
  req.on('error', function(er) {
    console.error('error on server request', er);
  });
  res.on('error', function(er) {
    console.error('error on server response', er);
  });
  res.writeHead(200);
  res.write('ready?\n');
  setTimeout(function() {
    res.end('go!\n');
    server.close();
  }, 100);
});

server.listen(1337, function() {
  var req = http.request({ host: 'localhost',
                           port: 1337,
                           path: '/',
                           method: 'GET' });

  req.on('error', function(er) {
    console.error('error on client request', er);
  });

  req.on('response', function(res) {
    res.on('error', function(er) {
      console.error('error on client response', er);
    });
    res.pipe(process.stdout);
  });

  req.end();
});

/*
$ ./node must-have-errors.js 
Agent { options: {},
  requests: {},
  sockets: {},
  maxSockets: 5,
  _events: { error: [] } }

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: EE without an error listener
    at Agent.emit (/Users/isaacs/dev/js/node-v0.6/must-have-errors.js:7:13)
    at Agent.<anonymous> (events.js:108:8)
    at new Agent (http.js:914:8)
    at http.js:1002:19
    at NativeModule.compile (node.js:546:5)
    at Function.require (node.js:514:18)
    at Function._load (module.js:296:25)
    at Module.require (module.js:354:17)
    at require (module.js:370:17)
    at Object.<anonymous> (/Users/isaacs/dev/js/node-v0.6/must-have-errors.js:13:12)
*/