Given a Gradle 8.6 build that applies `kotlin-dsl`...

# getting-started

[Vampire]

Given a Gradle 8.6 build that applies kotlin-dsl plugin and contains a pre-compiled script plugin (also had this with plain-old .kt file under same circumstances).

If I have simplified this code in the plugin:

val artifactsGetter: Provider<Configuration>.(Action<AttributeContainer>) -> Provider<ArtifactView> =
    { attributesAction -> map { it.incoming.artifactView { attributes(attributesAction) } } }

configurations
    .runtimeClasspath
    .artifactsGetter {
        attribute(ArtifactTypeDefinition.ARTIFACT_TYPE_ATTRIBUTE, ArtifactTypeDefinition.JAR_TYPE)
    }

It compiles perfectly fine.

But if I try to apply that plugin, I get

class Bar_gradle$$$result$1 cannot be cast to class org.gradle.api.Action (Bar_gradle$$$result$1 is in unnamed module of loader org.gradle.internal.classloader.VisitableURLClassLoader$InstrumentingVisitableURLClassLoader @649f4a9; org.gradle.api.Action is in unnamed module of loader org.gradle.internal.classloader.VisitableURLClassLoader @5f9d02cb)

If I look at the bytecode with javap what is generated is

final class Bar_gradle$$$result$1 extends kotlin.jvm.internal.Lambda implements kotlin.jvm.functions.Function1<org.gradle.api.attributes.AttributeContainer, kotlin.Unit> {

Does anyone have an idea why this is happening and whose "fault" it is?
Should I report this to Kotlin or Gradle?
Is there a generic work-around besides changing every case that fails at runtime to .artifactsGetter(Action { ... }) instead of .artifactsGetter { ... }?

(With Gradle 7.6.4 and thus KGP 1.7.10 it worked fine as long as the language version stayed at 1.4, but started to fail when I set it to 1.7, with Gradle 8.6 and thus KGP 1.9.20 it even fails with language version 1.4)

[edrd]

Looks like a Kotlin compilation issue. The lambda should have been compiled to a class that implements Action, shouldn’t it? At least is that how I thought SAM conversions worked.

[Vampire]

Me too, just wanted some reassurance before I create an issue 🙂

[Vampire]

https://youtrack.jetbrains.com/issue/KT-66621