events,test: fix TypeError in EventEmitter warning

Allows Symbol to be converted to String so it can be included in the
error.

Fixes: https://github.com/nodejs/node/issues/9003
PR-URL: https://github.com/nodejs/node/pull/9021
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/test/parallel/test-event-emitter-check-listener-leaks.js b/test/parallel/test-event-emitter-check-listener-leaks.js
index 1e357cd027..18d2d065b8 100644
--- a/test/parallel/test-event-emitter-check-listener-leaks.js
+++ b/test/parallel/test-event-emitter-check-listener-leaks.js
@@ -1,7 +1,7 @@
 'use strict';
 require('../common');
-var assert = require('assert');
-var events = require('events');
+const assert = require('assert');
+const events = require('events');
 
 var e = new events.EventEmitter();
 
@@ -13,6 +13,14 @@ assert.ok(!e._events['default'].hasOwnProperty('warned'));
 e.on('default', function() {});
 assert.ok(e._events['default'].warned);
 
+// symbol
+const symbol = Symbol('symbol');
+e.setMaxListeners(1);
+e.on(symbol, function() {});
+assert.ok(!e._events[symbol].hasOwnProperty('warned'));
+e.on(symbol, function() {});
+assert.ok(e._events[symbol].hasOwnProperty('warned'));
+
 // specific
 e.setMaxListeners(5);
 for (let i = 0; i < 5; i++) {