com.sun.tools.javac.util.Context class can't be found

[mars885]

Greetings.

I'm in a process of migrating my lib to the Kotlin 2.0 version and I've stumbled upon a blocker where my Java annotation processor's tests fail (both locally and on CI) with the following message:

e: [kapt] 'com.sun.tools.javac.util.Context' class can't be found ('tools.jar' is absent in the plugin classpath). Kapt won't work.

The following env & dependencies are used for tests:

• Kotlin: 2.0.0
• KSP: 2.0.0-1.0.24
• dev.zacsweers.kctfork:ksp:0.5.1
• JDK: corretto-1.8.0_412
• kapt4: false

The testing lib is set up like this:

private fun setupCompilation(
    sourceFiles: List<SourceFile>,
    processorType: ProcessorType,
): KotlinCompilation {
    val compilation = KotlinCompilation().apply {
        sources = sourceFiles
        verbose = false
        inheritClassPath = true
        languageVersion = "1.9"

        when (processorType) {
            ProcessorType.JAVAC -> annotationProcessors = listOf(HiltBinderJavacProcessor())
            ProcessorType.KSP -> configureKsp {
                symbolProcessorProviders.add(HiltBinderKspProcessor.Provider())
            }
        }
    }

    return compilation
}

The jdkHome and toolsJar properties from the KotlinCompilation class resolve to the correct paths when debugging:

• jdkHome -> /Users/paul/Library/Java/JavaVirtualMachines/corretto-1.8.0_412/Contents/Home
• toolsJar -> /Users/paul/Library/Java/JavaVirtualMachines/corretto-1.8.0_412/Contents/Home/lib/tools.jar

I've also verified that tools.jar does in fact exists in the path /Users/paul/Library/Java/JavaVirtualMachines/corretto-1.8.0_412/Contents/Home/lib/tools.jar.

Do you have an idea what's causing this? I've searched the Internet for answers, but nothing worked in my case.

[ZacSweers]

This is documented in the readme: https://github.com/ZacSweers/kotlin-compile-testing?tab=readme-ov-file#java-16-compatibility