in a KMM project, how to set java17 on the shared ...

# multiplatform

[brabo-hi]

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.

[Jacob Ras]

Add jvmToolchain(17)

[brabo-hi]

in which block

[Jacob Ras]

Sorry, was adding that 😬 It goes in the kotlin {} block.

[brabo-hi]

you mean having something like

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

[jw]

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)

[brabo-hi]

basically having

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

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

[Jacob Ras]

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 🙂

[brabo-hi]

thank you guys for your support

[eygraber]

@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

[jw]

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

[eygraber]

no reason to use anything but the latest locally

What about on CI?

[jw]

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

[eygraber]

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)?

[SanjayKarki]

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

[Michael Paus]

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

[jw]

I build everything with JDK 20

[Michael Paus]

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.

[jw]

my jvm target is usually set to 8 or 11

[Michael Paus]

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.