Why does ResolveLocale drop Unicode extension keys without values?

[anba]

var opt1 = new Intl.Collator("de-u-kn").resolvedOptions();
var opt2 = new Intl.Collator("de-u-kn-true").resolvedOptions();

print(`locale=${opt1.locale}, caseFirst=${opt1.numeric}`);
print(`locale=${opt2.locale}, caseFirst=${opt2.numeric}`);

The test case should print this per the current spec:

locale=de, caseFirst=true
locale=de-u-kn-true, caseFirst=true

I don't understand why the resolved locale of the first collator is not set to either de-u-kn or de-u-kn-true. If the current behaviour is not a spec bug, can we add a comment to clarify why Unicode extensions keys without values are removed from the resolved locale?

[littledan]

Huh, that's interesting.

Would fixing this be a matter of adding a simple step as ResolveLocale 8.h.ii.2.b Let supportedExtensionAddition be the concatenation of "-" and key ? If so, that sort of change sounds right to me.

(Aside: Wow, there's a lot of variation among implementations for how the locale presents these tags.)

[srl295]

caseFirst=${opt1.numeric}

should be numeric=${opt1.numeric}?

[littledan]

Rather than just making this one fix (which, in isolation, would seem good), let's see if we can make this part of a broader change. If that one doesn't seem feasible, we can come back and make this one fix.

[FrankYFTang]

I try to fix a bug in v8 and then my fix broke intl402/Collator/missing-unicode-ext-value-defaults-to-true.js and I reach the same conclusion this looks strange.
I would second we add to ResolveLocale https://tc39.github.io/ecma402/#sec-resolvelocale a step 8.h.ii.2.b as "Let supportedExtensionAddition be the concatenation of "-" and key."

[FrankYFTang]

Huh, that's interesting.

Would fixing this be a matter of adding a simple step as ResolveLocale 8.h.ii.2.b Let supportedExtensionAddition be the concatenation of "-" and key ? If so, that sort of change sounds right to me.

(Aside: Wow, there's a lot of variation among implementations for how the locale presents these tags.)

Yes, I think we should fix the spec this way.