fix: support import module in removeUnusedImports (GJF 1.30.0)

[arimu1]

Problem

java { removeUnusedImports() } / <removeUnusedImports/> fails on sources that use Java's import module (JEP 511), e.g.:

import module java.base;

class ModuleImportTest {
  void test() {
    UUID.randomUUID();
  }
}

with:

LINE_UNDEFINED removeUnusedImports(java.lang.IllegalArgumentException)
object of type com.sun.tools.javac.tree.JCTree$JCModuleImport is not an instance of com.sun.tools.javac.tree.JCTree$JCImport

Root cause: default google-java-format was still 1.28.0. Module-import support landed in google-java-format 1.30.0 (google/google-java-format#1213 / #1297), which skips JCModuleImport in RemoveUnusedImports instead of casting every import tree to JCImport.

Fixes #2890

Solution

• Default google-java-format remains 1.28.0 on JVM 17 (1.30.0 references JCAnyPattern, which only exists in JDK 21+ javac)
• Default bumps to 1.30.0 on JVM 21+
• Require at least 1.30.0 on JVM 25+ (Jvm.Support.addMin) for import module support
• Align gradle/libs.versions.toml compile coordinate with 1.30.0 (compile-only adapter)
• Regression tests for module imports (JDK 25+) and the new JVM 25 minimum

Users who pin an older GJF version on JVM 25 get a clear lint instead of a ClassCastException mid-format.

Testing

# JDK 17 — default stays 1.28.0 (1.30.0 would NoClassDefFoundError on JCAnyPattern)
JAVA_HOME=…/jbr-17 ./gradlew :testlib:test \
  --tests 'com.diffplug.spotless.java.RemoveUnusedImportsStep_withGoogleJavaFormatTest' \
  --tests 'com.diffplug.spotless.java.GoogleJavaFormatStepTest'
# 16 tests, 4 skipped — all green

# JDK 21 — default is 1.30.0
JAVA_HOME=…/jdk-21 ./gradlew :testlib:test \
  --tests 'com.diffplug.spotless.java.RemoveUnusedImportsStep_withGoogleJavaFormatTest' \
  --tests 'com.diffplug.spotless.java.GoogleJavaFormatStepTest'
# 16 tests, 4 skipped — all green

# JDK 25
JAVA_HOME=…/jdk-25 ./gradlew :testlib:test \
  --tests 'com.diffplug.spotless.java.RemoveUnusedImportsStep_withGoogleJavaFormatTest' \
  --tests 'com.diffplug.spotless.java.GoogleJavaFormatStepTest'
# moduleImports + versionBelowMinOnJava25IsNotAllowed green

Platform: macOS aarch64, JBR 17.0.14 + Temurin 21.0.12 + Temurin 25.0.4

Checklist

• summary under [Unreleased] in CHANGES.md, plugin-gradle/CHANGES.md, and plugin-maven/CHANGES.md
• link to issue java.removeUnusedImports does not handle import module correctly #2890
• allow edits from maintainers

[nedtwigg]

Seems like we're good on Java 21+ but this introduces a problem for Java 17. Not sure if it's a code problem or a tests problem.

[arimu1]

@nedtwigg This was a code problem, not a test problem.

The JDK 17 CI failures (NoClassDefFoundError: com/sun/tools/javac/tree/JCTree$JCAnyPattern) came from making google-java-format 1.30.0 the default on JVM 17. GJF 1.30.0 references JCAnyPattern, which only exists in JDK 21+ javac — so loading it on JDK 17 fails before any test assertion runs.

Fixed in 7bd31e1 by restoring the JVM-split defaults:

• JVM 17: default stays 1.28.0 (last GJF version that runs on JDK 17)
• JVM 21+: default 1.30.0
• JVM 25+: still requires ≥ 1.30.0 via addMin(25, "1.30.0") for import module support

Verified locally on JBR 17 and Temurin 21 — GoogleJavaFormatStepTest and RemoveUnusedImportsStep_withGoogleJavaFormatTest pass on both.