Hi there! I'm developing a library and recently I've upgraded: Kotlin from 1.6.10 to

1.9.20

, AGP from 7.2.1 to

7.4.2

and Gradle from 7.6.1 to

8.4

. After publishing the library version with the updates, a client reported that he can no longer build using the library due to:

e: C:/.../.gradle/caches/transforms-3/c84840751d0bf885b57987b97ba24946/transformed/jetified-kotlin-stdlib-1.9.20.jar!/META-INF/kotlin-stdlib-jdk7.kotlin_module: Module was compiled with an incompatible version of Kotlin. The binary version of its metadata is 1.9.0, expected version is 1.7.1.

even after deleting all caches. I have multiple android-only and multiplatform modules that are published, none has explicit declaration of kotlin-stdlib and I'm declaring: Android-only modules `build.gradle`:

android {
    compileOptions {
        targetCompatibility JavaVersion.VERSION_1_8
        sourceCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        languageVersion = '1.7'
        apiVersion = '1.7'
        jvmTarget = "1.8"
    }
}

Multiplaform modules `build.gradle.kts`:

kotlin {
    androidTarget {
        compilations.all {
            kotlinOptions {
                languageVersion = "1.7"
                apiVersion = "1.7"
                jvmTarget = "1.8"
            }
        }
    }

    sourceSets {
        all {
            languageSettings {
                languageVersion = "1.7"
                apiVersion = "1.7"
            }
        }
    }
}

Does any one know what could be causing this? And am I missing something to keep the library compatible with Kotlin 1.7?

Looks like your project depends by default on

kotlin-stdlib:1.9.20

which is not compatible with Kotlin compiler 1.7. I would advice you to configure

kotlin.coreLibrariesVersion = "1.7.0"

and related feature request

😮 I wasn't aware of that

kotlin.coreLibrariesVersion = "1.7.0"

property, and in fact I thought that declaring the languangeVersion/apiVersion would be enough. I'm going to try it, thank you!

hm, yes - it may happen