<i18n dev> RFR: 8289227: Support for BCP 47 Extension T - Transformed Content [v2]

[Joe Wang]

On Mon, 25 Jul 2022 16:10:02 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> This PR is to propose supporting the `T` extension to the BCP 47 to which `java.util.Locale` class conforms. There are two extensions to the BCP 47, one is `Unicode Locale Extension` which has been supported since JDK7, the other is this `Transformed Content` extension. A CSR has also been drafted.
>
> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed unnecessary `contains()` check

Looks good to me. Some minor comments below.

src/java.base/share/classes/java/util/Locale.java line 236:

> 234:  * particular Unicode locale attributes or key/type pairs.
> 235:  *
> 236:  * <h2><a id="t_extension">Transformed Content extension</a></h2>

Both the full name "Transformed Content extension" and the abbreviated forms "T Extension" are used in this document. I see Unicode and the RFC referred to it as "T Extension", " 't' Extension", and "Extension T". If we describe the extension as "T Extension", maybe we can make it clear in the title, e.g.:
     Transformed Content (T) Extension
     
could thus in the doc thereafter use "T Extension". The existing methods look like used full extension name, but for T Extension, the short form, e.g. getTExtensionFields also matches its javadoc ("Returns the map of fields in the T extension"). Your call.

src/java.base/share/classes/java/util/Locale.java line 265:

> 263:  * field separator (one alpha + one digit), followed by one or more subtags of the length 3 to 8,
> 264:  * each delimited by a hyphen.
> 265:  * <p>The transformed content information {@code source} language tag and {@code fields} are returned

"transformed content information" seems not needed as "The {@code source} language tag and {@code fields}" are known from the previous paragraph.

src/java.base/share/classes/sun/util/locale/TransformedContentExtension.java line 40:

> 38: public final class TransformedContentExtension extends Extension {
> 39: 
> 40:     public static final char SINGLETON = 't';

"singleton" as in "The singleton identifier" in the doc, seems to mean the key consists of a single character. But it can be confused with the Singleton pattern. T_EXTENSION_KEY (as methods such as isTransformedContentxxx expect a key) or Locale.TRANSFORMED_CONTENT_EXTENSION might be better.

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PR: https://git.openjdk.org/jdk/pull/9620