fix(socket): Fixes socket.use error packet which drops nodejs due to …

[serhiisol]

This PR fixes #2771

The kind of change this PR does introduce

• a bug fix

Current behaviour

Socket.use middleware drops nodejs process if error thrown in next function

New behaviour

Socket.use middleware sends error packet correctly without dropping nodejs instance.

Other information (e.g. related issues)

Socket cannot emit error event, because default behavior of EventEmitter will drop nodejs instance.
Details: https://nodejs.org/api/events.html#events_error_events

[darrachequesne]

Hi! Thanks for the PR. Actually, there seems to be an issue in the tests:

it('should pass errors', function(done){
  var srv = http();
  var sio = io(srv);

  srv.listen(function(){
    var socket = client(srv, { multiplex: false });

    socket.emit('join', 'woot');

    // + socket.on('error', function(err){
    // +   expect(err).to.be('Authentication error');
    // +  done();
    // + });

    sio.on('connection', function(socket){
      socket.use(function(event, next){
        next(new Error('Authentication error'));
      });
      socket.use(function(event, next){
        done(new Error('nope'));
      });

      socket.on('join', function(){
        done(new Error('nope'));
      });
      // - socket.on('error', function(err){
      // -   expect(err).to.be('Authentication error');
      // -   done();
      // - });
    });
  });
});

According to the docs:

Errors passed to middleware callbacks are sent as special error packets to clients.

Your first commit should be sufficient I think. Could you please update the tests, by renaming the 2nd socket?

[serhiisol]

Hi @darrachequesne, I noticed that after deep debugging, and I've updated PR with fixes. In the test clientSocket should listen to error event, but not server side one