JDepsGeneratorKt.majorJavaVersion throws IndexOutOfBoundsException on OpenJDK 15

[eiiches]

Hi, I'm trying to use https://github.com/graknlabs/bazel-distribution, which internally uses rules_kotlin, and got the following exception. The version of rules_kotlin is v1.5.0-alpha-3.

java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
        at java.base/java.util.Collections$SingletonList.get(Collections.java:4926)
        at io.bazel.kotlin.builder.tasks.jvm.JDepsGeneratorKt.majorJavaVersion(JDepsGenerator.kt:95)
        at io.bazel.kotlin.builder.tasks.jvm.JDepsGeneratorKt.access$majorJavaVersion(JDepsGenerator.kt:1)
        at io.bazel.kotlin.builder.tasks.jvm.JDepsGenerator.generateJDeps(JDepsGenerator.kt:55)
        at io.bazel.kotlin.builder.tasks.jvm.KotlinJvmTaskExecutor$execute$1$$special$$inlined$apply$lambda$3.invoke(KotlinJvmTaskExecutor.kt:123)
        at io.bazel.kotlin.builder.tasks.jvm.KotlinJvmTaskExecutor$execute$1$$special$$inlined$apply$lambda$3.invoke(KotlinJvmTaskExecutor.kt:33)
        at io.bazel.kotlin.builder.toolchain.CompilationTaskContext.execute(CompilationTaskContext.kt:148)
        at io.bazel.kotlin.builder.toolchain.CompilationTaskContext.execute(CompilationTaskContext.kt:140)
        at io.bazel.kotlin.builder.tasks.jvm.KotlinJvmTaskExecutor$execute$1.invoke(KotlinJvmTaskExecutor.kt:123)
        at io.bazel.kotlin.builder.tasks.jvm.KotlinJvmTaskExecutor$execute$1.invoke(KotlinJvmTaskExecutor.kt:33)
        at io.bazel.kotlin.builder.toolchain.CompilationTaskContext.execute(CompilationTaskContext.kt:148)
        at io.bazel.kotlin.builder.toolchain.CompilationTaskContext.execute(CompilationTaskContext.kt:140)
        at io.bazel.kotlin.builder.tasks.jvm.KotlinJvmTaskExecutor.execute(KotlinJvmTaskExecutor.kt:56)
        at io.bazel.kotlin.builder.tasks.KotlinBuilder.executeJvmTask(KotlinBuilder.kt:226)
        at io.bazel.kotlin.builder.tasks.KotlinBuilder.apply(KotlinBuilder.kt:129)
        at io.bazel.kotlin.builder.tasks.PersistentWorker.run(BazelWorker.kt:168)
        at io.bazel.kotlin.builder.tasks.BazelWorker.apply(BazelWorker.kt:74)
        at io.bazel.kotlin.builder.KotlinBuilderMain.main(KotlinBuilderMain.java:28)

It seems that we are failing to parse java.version property because the JVM is reporting 15 instead of 15.0 or 15.0.0.

rules_kotlin/src/main/kotlin/io/bazel/kotlin/builder/tasks/jvm/JDepsGenerator.kt

Lines 104 to 108 in 89a082c

	private fun String.majorJavaVersion(): Int {
	val (major, minor) = this.trim().split('.')
	val parsedMajor = Integer.parseInt(major)
	return if (parsedMajor == 1) Integer.parseInt(minor) else parsedMajor
	}

According to JEP 223: New Version-String Scheme,

The version number does not include trailing zero elements; i.e., $SECURITY is omitted if it has the value zero, and $MINOR is omitted if both $MINOR and $SECURITY have the value zero.

See Also: JDK-8231384: java.version system property doesn't contain minor/patch version anymore

Additional Info

$ bazel version
Build label: 4.0.0
Build target: bazel-out/k8-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Thu Jan 21 14:04:24 2021 (1611237864)
Build timestamp: 1611237864
Build timestamp as int: 1611237864

$ cat .bazelrc | grep build
build --java_runtime_version=remote_jdk15
build --java_language_version=15
build --javabase=@openjdk15_linux_archive//:runtime
build --host_javabase=@openjdk15_linux_archive//:runtime
build --java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla
build --host_java_toolchain=@bazel_tools//tools/jdk:toolchain_vanilla

http_archive(
    name = "openjdk15_linux_archive",
    build_file_content = """
java_runtime(name = 'runtime', srcs =  glob(['**']), visibility = ['//visibility:public'])
exports_files(["WORKSPACE"], visibility = ["//visibility:public"])
""",
    sha256 = "0a38f1138c15a4f243b75eb82f8ef40855afcc402e3c2a6de97ce8235011b1ad",
    strip_prefix = "zulu15.27.17-ca-jdk15.0.0-linux_x64",
    urls = [
        "https://mirror.bazel.build/cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-linux_x64.tar.gz",
        "https://cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-linux_x64.tar.gz",
    ],
)

http_archive(
    name = "io_bazel_rules_kotlin",
    urls = ["https://github.com/bazelbuild/rules_kotlin/releases/download/v1.5.0-alpha-3/rules_kotlin_release.tgz"],
    sha256 = "eeae65f973b70896e474c57aa7681e444d7a5446d9ec0a59bb88c59fc263ff62",
)

[eiiches]

I just upgraded the JDK to 15.0.2 and the issue is gone.

http_archive(
    name = "openjdk15_linux_archive",
    build_file_content = """
java_runtime(name = 'runtime', srcs =  glob(['**']), visibility = ['//visibility:public'])
exports_files(["WORKSPACE"], visibility = ["//visibility:public"])
""",
    sha256 = "be8ce1322bc8ded00374bd6ae1b9127d9b3547ccf526b7609bd63cdc49ac58bd",
    strip_prefix = "zulu15.29.15-ca-jdk15.0.2-linux_x64",
    urls = [
        "https://cdn.azul.com/zulu/bin/zulu15.29.15-ca-jdk15.0.2-linux_x64.tar.gz"
    ],
)