console.error is not a function #4467

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1. jasnell

   added

   eventsIssues and PRs related to EventEmitter and the events module.Issues and PRs related to EventEmitter and the events module.

   consoleIssues and PRs related to the console subsystem.Issues and PRs related to the console subsystem.

   on Dec 29, 2015
2. jasnell commented on Dec 29, 2015

   

   jasnell

   on Dec 29, 2015

   MemberAuthor

   More actions

   Same error does not occur using the repl:

   bash-3.2$ node
   > const EventEmitter = require('events');
   undefined
   > EventEmitter.defaultMaxListeners = 1
   1
   > class MyEmitter extends EventEmitter {}
   [Function: MyEmitter]
   > const myEmitter = new MyEmitter();
   undefined
   > myEmitter.on('event', ()=>{});
   MyEmitter {
     domain: 
      Domain {
        domain: null,
        _events: { error: [Function] },
        _eventsCount: 1,
        _maxListeners: undefined,
        members: [] },
     _events: { event: [Function] },
     _eventsCount: 1,
     _maxListeners: undefined }
   > myEmitter.on('event', ()=>{});
   (node) warning: possible EventEmitter memory leak detected. 2 event listeners added. Use emitter.setMaxListeners() to increase limit.
   Trace
       at MyEmitter.addListener (events.js:239:17)
       at repl:1:11
       at REPLServer.defaultEval (repl.js:248:27)
       at bound (domain.js:287:14)
       at REPLServer.runBound [as eval] (domain.js:300:12)
       at REPLServer.<anonymous> (repl.js:412:12)
       at emitOne (events.js:82:20)
       at REPLServer.emit (events.js:169:7)
       at REPLServer.Interface._onLine (readline.js:210:10)
       at REPLServer.Interface._line (readline.js:549:8)
   MyEmitter {
     domain: 
      Domain {
        domain: null,
        _events: { error: [Function] },
        _eventsCount: 1,
        _maxListeners: undefined,
        members: [] },
     _events: { event: [ [Function], [Function], warned: true ] },
     _eventsCount: 1,
     _maxListeners: undefined }
   > 
   
3. vkurchatkin commented on Dec 29, 2015

   

   vkurchatkin

   on Dec 29, 2015

   Contributor

   More actions

   Reproduces with:

   const EventEmitter = require('events');
   EventEmitter.defaultMaxListeners = 1;
   console.error('');

   console.error triggers some events. Documentation states:

   This class property lets you set it for all EventEmitter instances, current and future, effective immediately. Use with care.

   So this seems kind of expected.
4. davidvgalbraith

   added a commit that references this issue on Dec 30, 2015

   events: make sure console functions exist

   ...

   362d832
5. davidvgalbraith commented on Dec 30, 2015

   

   davidvgalbraith

   on Dec 30, 2015

   More actions

   So, node sets up the global objects e.g. console lazily to make startup really fast. The second call to myEmitter.on('event', ()=>{}); in your test.js wants to trigger console.error with that big message about max listeners detected. So it has to initialize the global console.
   The way these initializations work is they store an empty object as the global object, then eval the relevant file which fills in the properties of this object when it modifies module.exports. This is to prevent an infinite loop if you have a circular dependency.
   But console.js does module.exports = new Console(process.stdout, process.stderr);, which references process.stdout and process.stderr, causing a call to the stdout and stderr getters on lines 660 and 675 of src/node.js, which both call

         if ((stdout / stderr).isTTY) {
           process.on('SIGWINCH', function() {
   

   . The second one of these wants to trigger another warning about max listeners detected, so it has to initialize the global console. But there's already such an initialization in progress, which has cached an empty object in the global console, so this empty object is returned as the global console. An empty object doesn't have an error method, so you get this stack trace.

   There's no problem in the REPL because stdout and stderr aren't TTY, so these SIGWINCH events aren't added to process.

   I propose a fix at #4479.
6. jasnell

   closed this as completedin f9a59c1on Jan 15, 2016
7. evanlucas

   added a commit that references this issue on Jan 18, 2016

   events: make sure console functions exist

   ...

   a8330f7
8. scovetta

   added a commit that references this issue on Apr 2, 2016

   events: make sure console functions exist

   ...

   8cd93bf
9. sjarmak

   added a commit that references this issue on Jul 27, 2026

   events: make sure console functions exist

   ...

   f9a59c1