[Question] Difference in behavior wrt Chrome native impl

[vicb]

consider this:

      RSVP.Promise.resolve('rsvp').then(function(v) { throw v; });
      Promise.resolve('native').then(function(v) { throw v; });

In Chrome there would be a "Uncaught (in promise) native" exception while rsvp implementation does not throw.

I've labelled this as "Question" because I'm not sure what the ES6 spec says about it (it's cryptic to me).

Should rsvp throw or is the current implementation correct ?

[stefanpenner]

I've labelled this as "Question" because I'm not sure what the ES6 spec says about it (it's cryptic to me).

It's not part of the spec, but it is a "nice thing".

As RSVP is a typically meant to be included in larger projects this functionality is disabled by default. Although I am considering enabling it be default in 4.0.

example:

var rsvp = require('rsvp');
var Promise = rsvp.Promise;
Promise.reject(new Error('OMG'));
// => nothing

but when enabled: https://github.com/tildeio/rsvp.js#error-handling

rsvp.on('error', console.error.bind(console));

no rejection handler:

Promise.reject(new Error('OMG'));
// => [Error: OMG]

with sync error handler

Promise.reject(new Error('OMG')).catch(function(e) { });
// => nothing

with micro-task error handler

var a = Promise.reject(new Error('OMG'));

Promise.ressolve().then(function() {
  return a.catch(function(){ });
});
// => nothing

with macro-task error handler (false positive scenario)

var a = Promise.reject(new Error('OMG'));
setTimeout(function(){
  a.catch(function() { });
}, 0)

// => [Error: OMG]

The false positive and overall visibility problem let me to implement a full instrumentation API: https://github.com/tildeio/rsvp.js#instrumentation

Which lead to us implementing (for ember)

which was part of the inspiration for the chrome promise debugging (currently in canary). Although I am sad, as they did not expose this to user-land libs :(

[vicb]

@stefanpenner thanks for the detailed explanation. Closing as not a bug.

[stefanpenner]

@vicb thanks :). I believe this should be a default in 4.0 though

[stefanpenner]

i added it to the eventual 4.0 todo list #261