<i18n dev> RFR: 8174269: Remove COMPAT locale data provider from JDK

[Alan Bateman]

On Fri, 23 Feb 2024 21:24:10 GMT, Naoto Sato <naoto at openjdk.org> wrote:

> This PR intends to remove the legacy `COMPAT` locale data from the JDK. The `COMPAT` locale data was introduced for applications' migratory purposes transitioning to `CLDR`. It is becoming a technical debt and now is the time to remove it (we've been emitting a warning at JVM startup since JDK21, if the app is using `COMPAT`). A corresponding CSR has also been drafted.

>From a stewardship perspective I think we've done the right steps. To summarize:

- JDK 8 added the option to use CLDR locale data (JEP 127).
- JDK 9 switched to using CLDR locale data by default (JEP 252) with the option to run with -Djava.locale.providers=COMPAT and use the legacy/unmaintained locale data.
- JDK 21 added a warning when you run with -Djava.locale.providers=COMPAT announcing that this provider will be removed in a future release.
- With the proposal here, running with -Djava.locale.providers=COMPAT will print a warning to say that the configuration is ignored.

The reduction of 10Mb will be welcomed. There are likely projects that run their tests with the COMPAT provider. There may be some application deployments too. I've seen a few projects do changes in response to the run-time warning introduced in JDK 21 but there are likely projects/applications that will be "surprised" when they upgrade to JDK 23+ and tests fail. So I think one will need a bit of socialization and a loud release note.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17991#issuecomment-1962299087