Use `gradle-buildconfig-plugin` to generate dependency versions

[Goooler]

Generate build config for the versions like

spotless/lib/build.gradle

Line 99 in a0ac600

googleJavaFormatCompileOnly 'com.google.googlejavaformat:google-java-format:1.28.0'

And refer to the generated config for

spotless/lib/src/main/java/com/diffplug/spotless/java/GoogleJavaFormatStep.java

Line 124 in 8d4cd28

.add(17, "1.28.0"); // default version

There is an example like https://github.com/vanniktech/gradle-maven-publish-plugin/blob/d0e50fec7a07ef91fde62ae5cb0e4b4b4769d797/plugin/build.gradle.kts#L35-L110

This should be stacked on #2704.

[nedtwigg]

I'm not familiar with this, but I'm open to it. What is the problem that it solves?

[Goooler]

@renovate-bot send the updates like #2345, we have to update GoogleJavaFormatStep.java manually to reflect the latest version string. If we apply the build config stuff, the latest version in the lib will always be refed by

.add(17, BuildConfig.VERSION_GJF); // default version 

and BuildConfig.VERSION_GJF always reflects the latest version bumped by @renovate-bot.

[nedtwigg]

Wow! Great idea, I like it!

[builtbyjuls]

Hi, I would like to work on this. I reviewed current main now that #2704 has been merged, and the google-java-format defaults are now split by JVM compatibility.

Is the intended scope now to generate BuildConfig.VERSION_GJF from the version in libs.google.java.format and use it for the JVM 21+ recommended default, while keeping the JVM 17 default at 1.28.0 and the JVM 25 minimum at 1.30.0?

I would keep the dependency bump in #2706 outside this PR so the change remains focused on wiring the version catalog value into the generated build config.

[Goooler]

addMin(25, BuildConfig.VERSION_GJF) for

spotless/lib/src/main/java/com/diffplug/spotless/java/GoogleJavaFormatStep.java

Line 124 in 7bd31e1

.addMin(25, "1.30.0") // import module (JEP 511) requires google-java-format >= 1.30.0 (https://github.com/google/google-java-format/issues/1213)

Always ref the latest dependency version in the buildconfig

[builtbyjuls]

Thanks! One concern: if only the Java 25 minimum uses BuildConfig.VERSION_GJF, while the Java 21+ default remains hardcoded to 1.30.0, a future Renovate update would make Spotless select 1.30.0 and then reject it for being below the new minimum.

Should both the Java 21+ default and the Java 25 minimum use BuildConfig.VERSION_GJF, while Java 17 remains on 1.28.0?

[Goooler]

Good question! I was wrong. We should only replace

spotless/lib/src/main/java/com/diffplug/spotless/java/GoogleJavaFormatStep.java

Line 126 in 7bd31e1

.add(21, "1.30.0"); // default on JVM 21+ (1.30.0+ handles `import module` in RemoveUnusedImports on JVM 25+)

instead of addMin. That's the default one when users use googleJavaFormat.

I filed this FR a long time ago and haven't contributed to this codebase for a while, so I missed some context!