Unhandled rejection when joining chains with common rejected parent

[tjconcept]

Maybe I should do this kind of stuff in another way, but I've hit it a couple of times now and it's extremely hard to debug and, at least in my head, seems inconsistent and unintuitive.

var Promise = require('bluebird');

var a = Promise.try(function(){
    throw new Error('Something went wrong');
});

var b = Promise.try(function(){
    throw new Error('Something went wrong here as well');
});

var c = Promise
    .join(a, b)
    .spread(function( a, b ){
        return a+b;
    });

Promise
    .join(a, c)
    .spread(function( a, product ){
        // ...
    })
    .catch(Error, function(e){
        console.log(e);
    });

The workaround is to "silent" the a-chain in the last join with .catch(noop) (#483 in the future), but then c needs to know about the fact that a is part of c which is not always easy.

Does it make sense?

[benjamingr]

Can you check if this happens with the correct .join syntax?

[tjconcept]

It does not happen with join(a, c, fn), if that is what you mean?

I was not aware this was incorrect.. How come?

[benjamingr]

The old join syntax was deprecated and then superseded with the (a, b, fn) one a while ago.

That said, the face of still works (the old syntax) means that either:

• the behavior in terms of unhandled rejection tracking should be fixed
• 3.0 should remove it and give a big fat warning

Either is fine by me - the current behavior isn't good.

[tjconcept]

What were the reasons for deprecating the "old" syntax? I think it aligns nicely with .all, .props and so forth. How is it different?

How would I do something like this with the "new" syntax:

Promise.join(a, b).bind(console).spread(console.log)

[spion]

You can always use Promise.all

Promise.all([a,b]).bind(console).spread(console.log)

though when I proposed the original change for join I didn't really mean to suggest deprecating the old one - its just that it was much easier to model the type signatures in TypeScript for the new syntax

[tjconcept]

Hmm.. I really think of join and spread as two different things, just as resolve and then.
spread is calling the function with .apply or using the spread operator from ES6, regardless of the actual resolved value.
join is combining several values into an array of resolved values - like using rest parameters.

[tjconcept]

You can always use Promise.all

Seems like .all is giving me the same behaviour as .join().spread() with an uncaught exception.

[petkaantonov]

Yea it's a bug that I fixed a while ago in 3.0 with b182d5b . Maybe it could be backported

[petkaantonov]

Fixed in 2.9.28