What's the proper way to pass the

-Xexpect-actual-classes

flag to the compiler in 1.9.20-RC? Previously in 1.9.20-Beta2 I had:

kotlin {
    compilerOptions {
        freeCompilerArgs.add("-Xexpect-actual-classes")
    }
}

But this top-level

compilerOptions

has been removed now. I've tried

tasks.withType<KotlinCompile>().configureEach {
    compilerOptions {
        freeCompilerArgs.add("-Xexpect-actual-classes")
    }
}

and

tasks.withType<KotlinCompile>().configureEach {
    kotlinOptions {
        freeCompilerArgs += "-Xexpect-actual-classes"
    }
}

but still get the warning

'expect'/'actual' classes (including interfaces, objects, annotations, enums, and 'actual' typealiases) are in Beta. You can use -Xexpect-actual-classes flag to suppress this warning. Also see: https://youtrack.jetbrains.com/issue/KT-61573

during compilation.

Indeed, we decided to take more time to polish the top-level

compilerOptions

and it’s now postponed until 2.0 Please try using

kotlin {
    targets.all {
        compilations.all {
            compilerOptions.configure {
                freeCompilerArgs.add("-Xexpect-actual-classes")
            }
        }
    }
}

Thanks, this looks to work. What's the reason the other mechanisms to pass

freeCompilerArgs

don't work?

Did you see compilation errors (from Gradle) or red code in IDEA?

I see both Gradle compilation warnings and warnings in the IDE (not errors or red code, just warnings) using the mechanisms I tried. Both warnings go away with your method.

There is an unexpected reversal at https://youtrack.jetbrains.com/issue/KT-57292/Rework-configuration-of-compiler-settings-in-MPP-Projects

How can I fix it with Groovy Gradle and Kotlin 1.9.20?

kotlin {
    targets.all {
        compilations.all {
            compilerOptions.configure {
                freeCompilerArgs.add("-Xexpect-actual-classes")
            }
        }
    }
}

Gives:

> Ambiguous method overloading for method org.jetbrains.kotlin.gradle.targets.native.NativeCompilerOptions#configure.
  Cannot resolve which method to invoke for [class build_a61yfy2uoq4qbs0ma6w75b74a$_run_closure2$_closure4$_closure7$_closure8] due to overlapping prototypes between:
  	[interface kotlin.jvm.functions.Function1]
  	[interface org.gradle.api.Action]

is this supposed to work in KMP as well? Because for my generated code it doesnt look working..

kotlin {
    targets.all {
        compilations.all {
            compilerOptions.configure {
                freeCompilerArgs.addAll("-opt-in=kotlin.ExperimentalUnsignedTypes,kotlin.RequiresOptIn", "-Xexpect-actual-classes")
            }
        }
    }
}

Yep, the expect/actual flag works for me with KMP. I replaced

all

with

configureEach

, though.

targets.configureEach {
    compilations.configureEach {
        compilerOptions.configure {
            freeCompilerArgs.addAll("-opt-in=kotlin.ExperimentalUnsignedTypes,kotlin.RequiresOptIn", "-Xexpect-actual-classes")
        }
    }
}

same results

The thing with Action was needed for Groovy. For Kts the last code I posted works for me.