ci: add JDK 25 validation

[rpalcolea]

Add JDK 25 to CI test matrices (sbt and Maven jobs), a minimized25 test project, and version parsing coverage to confirm the compiler plugin works correctly on JDK 25.

Closes #857

Test plan

Environment

Component	Version
JDK	OpenJDK 25.0.2 (Zulu25.32+17-CA)
sbt	1.10.0
scip-java	0.12.3-1-8bf6b420-SNAPSHOT
OS	macOS Darwin 24.6.0

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What was changed

File	Change
build.sbt	Added minimized25 sbt project targeting JDK 25
.github/workflows/ci.yml	Added 25 to Java version matrix in both test and maven CI jobs
tests/unit/src/test/scala/tests/JavaVersionSuite.scala	Added version string parsing test case for "25.0.1"
tests/buildTools/src/test/scala/tests/GradleBuildToolSuite.scala	Added 25 to allJava list

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Test 1: Compiler plugin compiles under JDK 25

The minimized25 sbt project uses javaToolchainVersion := "25" and shares the same Java sources as all other minimized* projects (tests/minimized/src/main/java). It injects semanticdb-javac as a javac plugin via the agent and verifies it can compile real Java sources and emit SemanticDB output under JDK 25.

Command:

sbt minimized25/compile

Result:

[success] Total time: 14 s, completed Apr 3, 2026, 5:18:51 PM

Warnings observed were pre-existing and unrelated to JDK 25:

• sun.misc.Unsafe::arrayBaseOffset deprecation from protobuf (affects all JDK versions)
• source value 8 is obsolete from javac -source 8 flag (affects all JDK versions)

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Test 2: Version string parsing

JavaVersion parses the JVM version string from System.getProperty("java.version") to determine the major version. JDK 25 uses the format "25.0.x" (no 1. prefix), which is the same modern format introduced in JDK 9.

Command:

sbt "unit/testOnly tests.JavaVersionSuite"

Result:

tests.JavaVersionSuite:
  + 1.8.0_272   0.034s   // legacy 1.x format
  + 11.0.9      0.001s   // modern format
  + 25.0.1      0.000s   // new test case for JDK 25
Passed: Total 3, Failed 0, Errors 0, Passed 3

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Test 3: End-to-end indexing pipeline on JDK 25

This is the most comprehensive test. It exercises the full pipeline:

1. Maven compiles real Java sources with semanticdb-javac injected as a javac plugin
2. SemanticDB files are written to target/semanticdb-targetroot/
3. scip-java index-semanticdb reads the SemanticDB files and produces index.scip

Step 1 — Build and publish the CLI locally:

sbt build publishM2 publishLocal dumpScipJavaVersion
export SCIP_JAVA_VERSION=$(cat VERSION)
export SCIP_JAVA_CLI=$PWD/out/bin/scip-java

Step 2 — Compile examples/maven-example with the plugin:

cd examples/maven-example
mvn clean verify -DskipTests \
  -Dscip-java.version=$SCIP_JAVA_VERSION \
  sourcegraph:sourcegraphDependencies

Result:

[INFO] Dependencies were written to target/semanticdb-targetroot/com.sourcegraph_example_jar_1.0.0-SNAPSHOT.dependencies.txt
[INFO] BUILD SUCCESS
[INFO] Total time: 3.627 s

Step 3 — Convert SemanticDB to SCIP:

$SCIP_JAVA_CLI index-semanticdb target/semanticdb-targetroot

Step 4 — Verify output:

du -h index.scip

Result:

info: .../examples/maven-example/index.scip
4.0K	index.scip

index.scip was produced with non-zero size, confirming the full pipeline works on JDK 25.

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CI coverage

The CI matrix in .github/workflows/ci.yml now runs against [8, 11, 17, 21, 25] for both the test job (sbt) and the maven job, ensuring JDK 25 is validated on every future PR automatically.

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Why no code changes were needed in the core

The semanticdb-javac plugin uses only stable, long-lived APIs:

• com.sun.source.util.Plugin — the standard compiler plugin interface, stable since Java 8
• com.sun.source.util.TaskListener / TaskEvent.Kind.ANALYZE — hooks into the javac analysis phase, unchanged across versions
• javax.lang.model.* — the standard Java language model API, stable since Java 6

The --add-exports flags already present for Java 17+ (jdk.compiler/com.sun.tools.javac.*=ALL-UNNAMED) continue to apply and work correctly on JDK 25.

The roundToNearestStableRelease() method in JavaVersion.java already handles versions beyond 17 via a return version fallthrough — no explicit JDK 25 constant is required.