RFR: 8307547: Support variant collations [v4]

[Naoto Sato]

On Fri, 12 May 2023 16:41:20 GMT, Steven Loomis <srl at openjdk.org> wrote:

>>> I'm just wondering where a developer might go to get a definitive list, i.e. aside from this API note, how would they know that "-trad" or "-traditional" can be used to configure the ordering. Locale.forLanguageTag supports more than BCP 47 language tag strings so is this considered a private use language tag.
>> 
>> I think those should go into Oracle JDK's `Supported Locales` document. Created a task to include them (https://bugs.openjdk.org/browse/JDK-8308018)
>
>> > I'm just wondering where a developer might go to get a definitive list, i.e. aside from this API note, how would they know that "-trad" or "-traditional" can be used to configure the ordering. Locale.forLanguageTag supports more than BCP 47 language tag strings so is this considered a private use language tag.
>> 
>> I think those should go into Oracle JDK's `Supported Locales` document. Created a task to include them (https://bugs.openjdk.org/browse/JDK-8308018)
> 
> `-u-co` is defined [here](https://www.unicode.org/reports/tr35/#UnicodeCollationIdentifier) (UTS#35) and the keys are in the datafile [here (link to `main` branch!)](https://github.com/unicode-org/cldr/blob/main/common/bcp47/collation.xml) - note the `since=` attribute, these are very stable.
> 
> @AlanBateman 
>> Locale.forLanguageTag supports more than BCP 47 language tag strings
> 
> It should still be all valid BCP47 including extensions and private use (such as x-lvalue). 
> 
>> so is this considered a private use language tag
> 
> Not private use at all. The `-u-` subtag is registered, and the links above are from the registrar, see
> - https://www.rfc-editor.org/info/bcp47
> - https://www.rfc-editor.org/rfc/rfc6067

Thanks @srl295 
I am just curious how CLDR handles the default switch of Swedish collation. Now the `traditional` collation used to be `standard`, and `standard` used to be `reformed`. How do apps specify their desired collation in Swedish, regardless of CLDR versions?

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PR Comment: https://git.openjdk.org/jdk/pull/13917#issuecomment-1546042805