Wrong unhandledRejection event

[waldreiter]

The following program reproduces my problem:

const process = require('process');

process.on('unhandledRejection', function(reason) {
  console.log('unhandledRejection:', reason);
});

Promise
  .resolve('resolve')
  .then(function() {
    return Promise.reject('reject');
  })
  .catch(function(e) {
    console.log('catch:', e);
  });

// Promise.reject().catch(function(){});

This is the output:

catch: reject
unhandledRejection: reject

First the catch handler gets called, which is expected. But after that the unhandledRejection event handler gets called too, which is unexpected to me.

If the // on the last line are removed, then the unhandledRejection event handler gets not called. This line should have no effect on the first promise, but apparently it has.

Tested with v2.2.1 on OSX and linux.

[petkaantonov]

Without checking I would say this is a bug in V8 for not firing kPromiseHandlerAddedAfterReject when a rejected promise is followed.

[benjamingr]

@cody does the rejectionHandled event get called too?

[benjamingr]

I can't reproduce this in my platform - I only get catch: reject - which version of io.js are you running?

Update: Nevermind, this reproduces just fine.

[targos]

@benjamingr what is your platform ?
I can reproduce on win64. Result with rejectionHandled added:

D:\Desktop>node -v
v2.2.1

D:\Desktop>node test
catch: reject
unhandledRejection: reject
rejectionHandled: Promise { <rejected> 'reject' }

[benjamingr]

Who needs to be pinged on the v8 team?

[thefourtheye]

Can we start with @domenic?

[domenic]

Before calling this a V8 bug, we need a repro that is independent of the io.js code and just uses the V8 APIs.

[targos]

FWIW, the bug cannot be reproduced in Chrome's console

[vkurchatkin]

This issue should be fixed by a251657