events: removeListener event should be passed the user's listener function when using once() #5551

'use strict';

const assert = require('assert');
const EventEmitter = require('events');

const ee = new EventEmitter();

function myListener () {};

let addedType = null;
let addedListener = null;
let removedType = null;
let removedListener = null;

ee.on('removeListener', (type, listener) => {
  removedType = type;
  removedListener = listener;
});
ee.on('newListener', (type, listener) => {
  addedType = type;
  addedListener = listener;
});

ee.once('foo', myListener);

ee.emit('foo');

process.on('exit', () => {
  assert.equal('foo', addedType);
  assert.equal(addedListener, myListener);
  assert.equal('foo', removedType);
  process._rawDebug('next assertion will fail');
  assert.equal(removedListener, myListener);
});