newListener event

[smart--petea]

In http://nodejs.org/api/events.html is written:

Event: 'newListener'#
event String The event name
listener Function The event handler function
This event is emitted any time someone adds a new listener. It is unspecified if listener is in the list returned by emitter.listeners(event).

From this snippet I learnt that if listener is in listeners the newListener event is not fired.

I did

var EE = require('events');
var ee = new EE;

var fnOk = function(){}

ee.on('newListener', function(){
  console.log('NEW LISTENER', arguments);
})

ee.on('ok' , fnOk); //fnOk is in ee.listeners('ok')
ee.on('ok', fnOk);

event newListener is fired twice in spite of fact that listener is just in listeners array.

May be I am wrong.

[skenqbx]

This is either a bug in the EE or in the docs.
There are no checks in addListener() if the listener is already registered for the specific event. Additionally, removeListener() has to be called twice to remove both listeners.

[jasnell]

Well, to be fair, the docs say that the behavior is "unspecified" if the listener is already added. It does not actually say that the event won't be fired multiple times. Still, this behavior feels a bit wonky and ought to be looked at.

[sam-github]

You misread the admittedly poorly worded docs: https://github.com/joyent/node/pull/8883/files#r21945241

[jasnell]

Hmm.. hard to misread something so poorly written in the first place ;-). To be certain, the docs say nothing about the listener being added multiple times. I'll admit, it tends towards a "doctor, it hurts when I do this" kind of situation, but the docs are obviously lacking here.

[jasnell]

Resolved in the io.js docs. Will pick up the change from there in the converged repo