New plugin: 'com.palantir.baseline-enable-preview-flag'

[iamdanfox]

Before this PR

I have a PR up internally on template-witchcraft#1414 which demonstrates how verbose it is to opt-in to feature previews, e.g. records. As described in this stackoverflow answer, I had to add:

tasks.withType(JavaCompile) {
    options.compilerArgs += "--enable-preview"
}
tasks.withType(Test) {
    jvmArgs += "--enable-preview"
}
tasks.withType(JavaExec) {
    jvmArgs += "--enable-preview"
}

Which was pretty lame. Additionally, you'd have to add this to every project.

After this PR

==COMMIT_MSG==
Add the new line apply plugin: 'com.palantir.baseline-enable-preview-flag' to your subprojects block to enable the usage of unreleased java features (e.g. records, switch expressions, var keyword etc).

Note, this plugin is a no-op on any project where you have a low sourceCompatibility.
==COMMIT_MSG==

cc @robert3005 who usually likes shiny new things

Possible downsides?

• I think the decision to start using unstable java features should be taken quite cautiously, as I really don't want to find abandoned projects which are deeply coupled to some exotic unstable feature which has since been changed/removed. I think the rule-of-thumb for using this is if you really had to back it out, you could undo it all in a day.
• For a moment, I wondered if actually the verbosity of enabling this stuff is actually desirable, but it occurred to me that people will just copy and paste these snippets everywhere and then we'll be completely screwed. Better to have a one-liner which is easy to excavate

[changelog-app]

Generate changelog in changelog/@unreleased

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Add the apply plugin: 'com.palantir.baseline-enable-preview-flag' to your subprojects block to enable the usage of unreleased java features (e.g. records, switch expressions, var keyword etc).

Note, this plugin is a no-op on any project where you have a low sourceCompatibility.

Check the box to generate changelog(s)

• Generate changelog entry

[fawind]

Looks good!

Need to double check but do we also need to set the preview flag for the javadoc task?

Edit: Tried it and we also need to set preview on javadoc. Something like:

tasks.withType(Javadoc) {
    options.addBooleanOption('-enable-preview', true)
    options.addStringOption("source", SOURCE_COMPAT)
}

[fawind]

Javadoc is just nasty. But looks good!

[svc-autorelease]

Released 3.52.0