[strawman] Symbol.thenable proposal

[Isiah Meadows]

Not sure how this is relevant, since this is about types rather than
identity, and I'd say typing values is *far* from a solved problem
beyond the basic concept of "all values have a type"...\* ;-)

\* https://en.wikipedia.org/wiki/Type_system

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Isiah Meadows
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On Sat, Apr 14, 2018 at 5:59 PM, Claude Petit <petc at webmail.us> wrote:
> I don't want to be annoying, but object identity is something solved since a long long time by classical OOP   ¯\_(ツ)_/ ¯   But I might by "wrong" as usual...
>
> -----Original Message-----
> From: Isiah Meadows <isiahmeadows at gmail.com>
> Sent: Friday, April 13, 2018 9:01 PM
> To: Jordan Harband <ljharb at gmail.com>
> Cc: es-discuss <es-discuss at mozilla.org>
> Subject: Re: [strawman] Symbol.thenable proposal
>
> I can't remember where, but I recall seeing this discussed elsewhere (maybe in the TC39 meeting notes?) and the conclusion was basically
> ¯\_(ツ)_/¯. I'm not convinced myself it's actually worth the extra symbol just to make something not considered a thenable - all these Promise libraries have been able to get away with it for this long; what makes ES promises any different here? (Dynamic import is probably the only possible case I can think of short certain proxies in terms of things that could be considered thenables but shouldn't always.)
>
> Worst case, you can just return a value that happens to have a promise in a property, like in `{value: somePromise}` - nobody resolves that except `co` IIRC.
> -----
>
> Isiah Meadows
> me at isiahmeadows.com
>
> Looking for web consulting? Or a new website?
> Send me an email and we can get started.
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> On Fri, Apr 13, 2018 at 4:20 PM, Jordan Harband <ljharb at gmail.com> wrote:
>> `await import(path)` wouldn't ever be able to do anything besides
>> Promise.resolve; I'm pretty confident that this proposal, or something
>> like it, is the only possibility to make ModuleRecords (for modules
>> that export a `then` function) not be considered thenable.
>>
>> On Fri, Apr 13, 2018 at 8:02 AM, Guy Bedford <guybedford at gmail.com> wrote:
>>>
>>> It's worth noting that the driving use case here is coming from
>>> NodeJS development hitting issues where the guaranteed result for
>>> dynamic import resolution can't be assumed to be a module namespace,
>>> although please correct me if I'm wrong here Gus.
>>>
>>> Alternatively could this mitigation be handled by creating a
>>> `Promise.resolveStrict` primitive that explicitly opts-out of
>>> thenable resolution in the promise chain?
>>>
>>> I'd think we are getting further and further away now from
>>> third-party promise implementation interops, that such approaches
>>> might make sense to consider at this point, in the name of returning
>>> to more well-defined semantics.
>>>
>>> On Fri, Apr 13, 2018 at 3:33 AM Gus Caplan <me at gus.host> wrote:
>>>>
>>>> Hello all,
>>>>
>>>> In an effort to curtail the interesting behavior of Promise.resolve
>>>> (especially with regard to dynamic import), I have created a
>>>> proposal for a well-known symbol which will allow an object to not
>>>> be treated as a "thenable."
>>>>
>>>> I am privy to the current protocol proposal which might be a better
>>>> fit for this, but due to dynamic import already being stage 3, I
>>>> don't feel we should wait for it to come to fruition.
>>>>
>>>> Comments and suggestions are of course quite welcome at the repo [1].
>>>>
>>>> Thanks,
>>>> -Gus
>>>>
>>>> [1]: https://github.com/devsnek/proposal-symbol-thenable
>>>>
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