[lworld] RFR: 8377101: [lworld] Automatically generate value class sources based on source annotations

[David Beaumont]

On Fri, 27 Feb 2026 11:37:12 GMT, David Beaumont <duke at openjdk.org> wrote:

> Adds a new AnnotationProcessor to read the @MigratedValueClass on prospective value classes and generate the equivalent source file with the 'value' keyword at each annotated class declaration.
> 
> This adds new PROCESSOR_PATH variable to the compilation macro and use it for annotation processing.
> This also requires moving the plugin discovery path to the new variable (was in classpath before) because the addition of a '--processor-path' flag disables using the classpath for plugin discovery.
> 
> For now this is all limited to `java.base` but that's expandable later easily. There was an issue just enabling it for all modules however (esp. `jdk.incubator` which might be special).
> 
> While there is currently no specific unit test for this code, if it were to fail to generate the correct value classes, a lot of other downstream tests would fail.

Now I see there are tests in `test/jdk/valhalla/valuetypes`, I'm wondering if the annotation processor should (at least temporarily) be in:

`make/jdk/src/classes/build/tools/valhalla/valuetypes`
rather than:
`make/jdk/src/classes/build/tools/valueclasses`

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PR Comment: https://git.openjdk.org/valhalla/pull/2180#issuecomment-3972811919