RFR: CODETOOLS-7903008: JMH: Support incremental annotation processing for Gradle Java plugin

[Taylor Wicksell]

On Thu, 10 Jun 2021 17:53:42 GMT, Taylor Wicksell <github.com+301239+twicksell at openjdk.org> wrote:

> This change adds support for Gradle's [incremental annotation processing](https://docs.gradle.org/current/userguide/java_plugin.html#sec:incremental_annotation_processing). Without this support, developers using the JMH annotation processor in their Gradle projects will see their compilation time increased due to Gradle invalidating its incremental compilation cache.

Unfortunately I had to test this manually by performing a `mvn install` of my branch and using that with a couple of my own gradle projects.  If you run gradle with `--info` and you will see:

Full recompilation is required because org.openjdk.jmh.generators.BenchmarkProcessor is not incremental. Analysis took 0.085 secs.


After applying this change, you will see:

Created classpath snapshot for incremental compilation in 0.391 secs. 1153 duplicate classes found in classpath (see all with --debug).


I don't have a great way to add a test case to JMH for this, as I suspect you wouldn't want all of those gradle specifics as part of your build. But open to suggestions here.

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PR: https://git.openjdk.java.net/jmh/pull/43