[MCOMPILER-595] Enable parameter metadata by default

[wilx]

Summary

• Enable -parameters by default for both compiler:compile and compiler:testCompile.
• Document that maven.compiler.parameters=false opts out of parameter-name metadata.
• Extend the MCOMPILER-298 integration test to verify both the new default and the explicit opt-out.

Motivation

More frameworks rely on reflection to obtain method parameter names. Generating that metadata by default makes those names available without requiring every project to opt in explicitly, while retaining a configuration switch for projects that do not want the metadata.

Fixes #858

Validation

JAVA_HOME=/opt/jdks/latest-21 /opt/maven/latest-4/bin/mvn -ntp -Prun-its -Dinvoker.test=MCOMPILER-298 clean verify

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[desruisseaux]

In Maven 3, the Maven Compiler Plugin often overwrote the default options of the standard javac command with Maven's own opinion of what these defaults should be. The consequence was, for example, arbitrary and non-obvious default values for the -target option.

In the 4.x line of Maven Compiler Plugin, a design goal so far was to have the same defaults as the standard javac command. A javac option is not added unless explicitly requested, in an attempt to be less surprising for developers who read the Oracle javac man page. This pull request would be a first breach in this attempt to be consistent.

Given that the default value of this parameter can be set by the maven.compiler.parameters property, would it be okay for projects who want such default to specify it in a parent pom.xml?

[wilx]

While I have to enable it all the time for Spring Framework, I can deal with it. I saw the #858 and ran with it. I guess both the PR and the issue should be closed then.

[desruisseaux]

Thanks. I'm closing this pull request on the basis of consistency with default behaviour of standard javac. I re-targeted #858 to 3.x since the 3.x line of the Compiler Plugin already has defaults that diverge from javac defaults. Therefore, maybe the question of whether to provide this default is still open for 3.x.