pdubroy / checked-emitter Goto Github PK

When adding a listener that throws an error, the listeners following after the failed listener are not triggered (#1). Moreover, the the error bubbles to the point where emit() was executed and interrupts the outer program flow too (#2).

Test case:

test('failing listeners', t => {
  let e = new CheckedEmitter();
  let x = false;
  let y = false;

  e.registerEvent('trigger');
  e.addListener('trigger', () => { throw new Error(); x = true; });
  e.addListener('trigger', () => { y = true; });
  e.emit('trigger'); // (#2) should continue and not stop here

  t.equal(x, false, 'x was not changed');
  t.equal(y, true, 'y was changed'); // (#1) should reach the second listener

  t.end();
});

test

In the current implementation, this._checkEventType(eventType, callback, 'callback arity'); is checked twice when adding a listener with once(). The first time, it succeeds (in CheckedEmitter.prototype.once) but once the call is forwarded to CheckedEmitter.prototype.addListener with a wrapped callback created in the FB library, it fails when checkin the arity (the wrapper that got created has no arguments whereas the event might have some).

TypeError: Wrong callback arity for 'x': expected 1, got 0
   at CheckedEmitter._checkEventType (./checked-emitter/index.js:60:13)
   at CheckedEmitter.addListener (./checked-emitter/index.js:70:8)
   at CheckedEmitter.once (./checked-emitter/node_modules/fbemitter/lib/BaseEventEmitter.js:81:17)
   at CheckedEmitter.once (./checked-emitter/index.js:76:27)