Integrate with Intl.DurationFormat

[ryzokuken]

#129 (comment) never really took Duration into account from what it seems, we should discuss this in a meeting.

[sffc]

We have an open proposal to add Intl.DurationFormat:

https://github.com/younies/proposal-intl-duration-format

[ptomato]

Discussed in the March 19 meeting: We'll update the Intl.DurationFormat in our polyfill to match the one in the proposal as needed.

@ryzokuken Should this issue remain open to implement that, or is it more something that will be done on an ongoing basis as other issues are fixed?

[littledan]

I'm leaving out the Stage 3 milestone; I think the integration at both the spec and polyfill levels are more milestones for Intl.DurationFormat, and don't block Stage 3 or polyfill distribution for Temporal.

[anba]

Should implementers go ahead and provide locale-sensitive Duration.prototype.toLocaleString even without an official spec (PR)? We've already received two reports about why Duration.prototype.toLocaleString just returns the same result as Duration.prototype.toString (https://bugzilla.mozilla.org/show_bug.cgi?id=1839694#c4, https://bugzilla.mozilla.org/show_bug.cgi?id=1942850).

Maybe there's confusion because the Temporal polyfill already provides locale-sensitive Duration.prototype.toLocaleString (when Intl.DurationFormat is available)?

[dminor]

Alternatively, maybe the polyfill should remove this behaviour until it has been specified, to avoid causing confusion.

@ptomato This is a potential blocker for us to be able to ship Temporal. Would it be possible for the champions to have a look at this and give us some guidance on the best way to proceed?

[sffc]

Intl.DurationFormat is Stage 4 (although the PR hasn't been merged yet).

So it should be safe to add toLocaleString to the Stage 3 Temporal proposal.

CC @ryzokuken

[ptomato]

I'll take a look at this next week.

[ptomato]

@dminor @anba This is done in #3088, which is based on the current stage 4 state of Intl.DurationFormat in tc39/ecma402#943. Hopefully this is what you need!

I'd be interested in your opinion on whether it needs to wait for tc39/ecma402#943 before merging or you'd be happy with merging it now.

[anba]

I'd be interested in your opinion on whether it needs to wait for tc39/ecma402#943 before merging or you'd be happy with merging it now.

I don't think this needs to wait for tc39/ecma402#943.