async/await improvements

C. Scott Ananian ecmascript at
Wed Nov 12 08:17:44 PST 2014

On Wed, Nov 12, 2014 at 11:08 AM, Axel Rauschmayer <axel at> wrote:
> Is that true, though? Couldn’t a finalizer or something similar check
> (before a promise is garbage collected) whether all errors have been
> handled?

A finalizer can do this check.  This will flag some uncaught
exceptions, but not promptly.  And as I wrote above, that's only part
of the issue -- promises can also be kept alive for an indefinite
period of time, but never end up either handling their exceptions or
becoming unreachable.  This could also be an error.

That is, liveness is one way to tell that an exception will never be
handled, but it is only an approximation.

And it's not necessarily an error to not handle an exception --
`Promise.race()` is expected to have this behavior as a matter of
course, for example.

We've been through this discussion many times before.  Eventually
there may be a `Promise#done`.  But the consensus was that the first
step was to give the devtools folks time to make good UI for showing
the dynamic "unhandled async exception" state of a program, and see
how well that worked.

ps. some of the discussed language features threaten to release zalgo.
but i'll not open up that can of worms.

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