I am trying to use a preview JDK in my Kotlin comp...

# gradle

[Gavin Ray]

I am trying to use a preview JDK in my Kotlin compiler config, but I am getting a strange error. Has anyone seen this before:

val JDK_21_PATH = "/home/user/.sdkman/candidates/java/21.ea.6-open"

tasks.withType<org.jetbrains.kotlin.gradle.tasks.UsesKotlinJavaToolchain>().configureEach {
    kotlinJavaToolchain.jdk.use(JDK_21_PATH, JavaVersion.VERSION_21)
}

Execution failed for task ':app:compileKotlin'.
> Error while evaluating property 'compilerOptions.jvmTarget' of task ':app:compileKotlin'.
   > Failed to calculate the value of property 'jvmTarget'.
      > Unknown Kotlin JVM target: 21

[Gavin Ray]

Specifically, I am trying to build around the changes present in the Foreign Function & Memory API since it's significantly changed since JDK19 LTS

[Gavin Ray]

(Otherwise I would just use JDK19)

[tapchicoma]

JavaVersion.VERSION_21 was added in Gradle 7.6

[Gavin Ray]

I'm using Gradle 8.0

[Gavin Ray]

distributionUrl=https\://services.gradle.org/distributions/gradle-8.0-rc-1-bin.zip

[tapchicoma]

sorry, it is about Kotlin JVM Target...

Kotlin does not yet have jvm target 21 in it. Probably, better for now to use JavaTarget.VERSION_19 as task input but still point to JDK 21 location

[Gavin Ray]

Ohh, I didn't know you could do that 🤦

[Gavin Ray]

Ty, that makes sense, since the bytecode version does not need to be 21, just the JDK API right?

[tapchicoma]

it is only in this specific case - KGP does not check that JDK version is the same as provided one

[Gavin Ray]

This is a great trick to know

[Gavin Ray]

Oh wait hmm, it still seems to fail with that 🤔

val JDK_21_PATH = "/home/user/.sdkman/candidates/java/21.ea.6-open"

tasks.withType<org.jetbrains.kotlin.gradle.tasks.UsesKotlinJavaToolchain>().configureEach {
    kotlinJavaToolchain.jdk.use(JDK_21_PATH, JavaVersion.VERSION_19)
}

[Gavin Ray]

I think maybe you just cannot use preview JDK's with kotlin + gradle?

[Gavin Ray]

(I think Maven too, I remember trying once)

[tapchicoma]

what is the failure?

[Gavin Ray]

Same as before =/

[user@MSI bustub-kotlin]$ ./gradlew compileKotlin                                                                                                            
> Task :app:compileKotlin FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:compileKotlin'.
> Error while evaluating property 'compilerOptions.jvmTarget' of task ':app:compileKotlin'.
   > Failed to calculate the value of property 'jvmTarget'.
      > Unknown Kotlin JVM target: 21

[Gavin Ray]

Caused by: java.lang.IllegalArgumentException: Unknown Kotlin JVM target: 21
        at org.jetbrains.kotlin.gradle.dsl.JvmTarget$Companion.fromTarget(JvmTarget.kt:26)
        at org.jetbrains.kotlin.gradle.tasks.DefaultKotlinJavaToolchain$wireJvmTargetToToolchain$1$1.invoke(DefaultKotlinJavaToolchain.kt:78)
        at org.jetbrains.kotlin.gradle.tasks.DefaultKotlinJavaToolchain$wireJvmTargetToToolchain$1$1.invoke(DefaultKotlinJavaToolchain.kt:70)
        at org.jetbrains.kotlin.gradle.tasks.DefaultKotlinJavaToolchain$sam$org_gradle_api_Transformer$0.transform(DefaultKotlinJavaToolchain.kt)

[tapchicoma]

strange, it should pickup JavaVersion.VERSION_19 for Jvm Target

[tapchicoma]

do you have a repro?

[Gavin Ray]

https://scans.gradle.com/s/ol3nejng5j6lw

[Gavin Ray]

Sure, I can make a repro, one moment

[Gavin Ray]

bustub-kotlin.zip

bustub-kotlin.zip

[Gavin Ray]

(You will have to install Java 21ea build 6 with sdk install java 21.ea.6-open and replace the path constant)

[tapchicoma]

hm, I only see this error:

Execution failed for task ':app:compileKotlin'.
> 'compileJava' task (current target is 11) and 'compileKotlin' task (current target is 19) jvm target compatibility should be set to the same Java version.
  Consider using JVM toolchain: <https://kotl.in/gradle/jvm/toolchain>

but it is possible to disable via kotlin.jvm.target.validation.mode=ignore

[tapchicoma]

after it I see just a normal compilation errors

[Gavin Ray]

That's so strange, something must be up on my system

[Gavin Ray]

Thanks for looking into it

[Gavin Ray]

Out of curiosity, does setting the JDK toolchain to Java 21 also work for you 🤔

[Gavin Ray]

java {
    toolchain{
        languageVersion.set(JavaLanguageVersion.of(21))
    }
}

[tapchicoma]

yes, I've used the same JDK from SDKMAN as in example

[Gavin Ray]

Does it compile with just that as well?

[tapchicoma]

nope:

App.kt:12:26 Unresolved reference: MemorySession

[tapchicoma]

and so on with the same error

[Gavin Ray]

ahh okay, so that means it does work (those were removed)

[Gavin Ray]

since it's not gradle error

[Gavin Ray]

man something is VERY broke with my gradle

[Gavin Ray]

maybe something strange with Gradle Windows/WSL2

[Gavin Ray]

Thank you so much for looking into it, I very much appreciate your time 🙏