872267 - EventEmitter stops on errors

Status: RESOLVED WONTFIX

(L20n :: JS Library, defect, P3)

Description

[Zibi Braniecki [:zbraniecki][:gandalf]]

If EventEmitter's callback throws, EE breaks.

Example code:

var ctx = L20n.getContext();
ctx.addResource('<browser "foo">');
ctx.addEventListener('ready', function() {
  console.log(1);
  console.log(y); // error
});
ctx.addEventListener('ready', function() {
  console.log(2); // never fired
});
ctx.freeze();

Two possible solutions:
 - wrap each listener execution in setTimeout
 - or try...catch

Comment 1

[Staś Małolepszy :stas]

How does node get away without any of these solutions?

https://github.com/joyent/node/blob/master/lib/events.js#L119

Comment 2

[Zibi Braniecki [:zbraniecki][:gandalf]]

it does not.

Code like:

var events = require("events");
var ee = new events.EventEmitter();


ee.addListener('ready', function() {
  console.log(1);
  console.log(y); // throws
});

ee.addListener('ready', function() {
  console.log(2);
});
ee.emit('ready');
console.log('a');


will throw and never reach 2

Comment 3

[Zibi Braniecki [:zbraniecki][:gandalf]]

is it a wontfix?

If other libraries do that, maybe we should just accept that it's the expected behavior?

Comment 4

[Axel Hecht [:Pike]]

Yeah, I think it's common behavior. Same happens in twisted in python land, too. If your callback errors, the event loop hangs.