in a KMM project, how to set java17 on the shared module? i have the following

kotlin {
    androidTarget {
        compilations.all {
            kotlinOptions {
                jvmTarget = "17"
            }
        }
    }

i am getting the following error

'compileDebugJavaWithJavac' task (current target is 1.8) and 'compileDebugKotlinAndroid' task (current target is 17) jvm target compatibility should be set to the same Java version.

Add

jvmToolchain(17)

in which block

Sorry, was adding that 😬 It goes in the

kotlin {}

block.

you mean having something like

kotlin {
    androidTarget {
        compilations.all {
            kotlinOptions {
                jvmTarget = "17"
            }
        }
    }
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(17))
    }
}

A toolchain declaration will force the presence of JDK 17 rather than allowing any JDK 17 or newer to build your project. The Java compiler is designed to cross-compiler older releases. I would not recommend forcing old JDKs as there really should be no reason to use anything but the latest locally (or maybe N-1 while waiting for Gradle support). You can set the Java compiler compatibility with

android {
  compileOptions {
      sourceCompatibility(JavaVersion.VERSION_17)
      targetCompatibility(JavaVersion.VERSION_17)

basically having

android {
    compileOptions {
        sourceCompatibility(JavaVersion.VERSION_17)
        targetCompatibility(JavaVersion.VERSION_17)
    }
}

kotlin {
    androidTarget {
        compilations.all {
            kotlinOptions {
                jvmTarget = "17"
            }
        }
    }
}

I checked, in my projects I have:

android {
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_17
        targetCompatibility = JavaVersion.VERSION_17
    }
    kotlinOptions {
        jvmTarget = "17"
    }

I was very sure I was using the toolchain, forgot I later updated it; removing it in favour of what Jake said 🙂

thank you guys for your support

@jw is there a way to enforce a minimum JDK version for building the project other than toolchains? Another nice thing about them is provisioning, which is helpful when onboarding iOS devs

I suppose you could detect the JDK version invoking Gradle and conditionally set a toolchain if it was too low

no reason to use anything but the latest locally

What about on CI?

The same. Why would you use an old version? You're deliberately using something slower and with fewer features.

So for example in SqlDelight is there a technical reason the toolchain is set to 17, or is that something that can be configured with what you said above (conditionally set a toolchain if the version invoking Gradle is too low)?

just change all 17 to 1.8and it should work fine while changing to 17 i also faced the same issue

What is currently the highest version which is still compatible with Android?

I build everything with JDK 20

How do you do that? I only get

Execution failed for task ':shared:compileKotlinDesktop'.
> Error while evaluating property 'compilerOptions.jvmTarget' of task ':shared:compileKotlinDesktop'.
   > Failed to calculate the value of property 'jvmTarget'.
      > Unknown Kotlin JVM target: 20
when I try.

my jvm target is usually set to 8 or 11

Ahhh, I interpreted “build everything with JDK 20” as meaning really everything, i.e,, including the jvm target. At least I can confirm now that “everything” works with JDK 17, even on Android.