I have a problem importing my kmp lib to my sample project.

Project

I have the following code structure :

├── app/ (KMP App module containing my samples apps)
│   ├── commonMain/
│   ├── androidMain/
│   └── jsMain/
├── myLib/ (KMP module for my library)
│   └── commonMain/
└── libs/ (myLib compiled as files)
    ├── myLib-release.aar
    ├── myLib-metadata.jar
    └── myLib-js.klib

Steps

What I try to do is building myLib to files and importing it in the commonMain folder of my samples app (to access it from commonMain, jsMain & androidMain).

1. I build myLib. Here is my myLib/build.gradle file :

plugins {
    alias(libs.plugins.kotlinMultiplatform)
    alias(libs.plugins.android.library)
}

val sdkVersion = "1.2.0"

kotlin {
    androidTarget {
        version = sdkVersion

        @OptIn(ExperimentalKotlinGradlePluginApi::class)
        compilerOptions {
            jvmTarget.set(JvmTarget.JVM_21)
        }
    }
    js {
        browser {
            version = sdkVersion
            binaries.executable()
        }
    }
    withSourcesJar()

    sourceSets {
        commonMain {
            dependencies {
                ...
            }
        }
    }
}

android {...}
dependencies {...}

tasks.withType<Jar> {
    manifest {
        attributes["Implementation-Title"] = "myLib-${sdkVersion}"
        attributes["Implementation-Version"] = sdkVersion
    }
}

2. I retrieve the generated files in the ./myLib/build/ folder and extract them to ./libs/

3. I import them in my sample module. Here is the app/build.gradle :

kotlin {
    androidTarget {...}

    js {...}

    sourceSets {
        androidMain.dependencies {
            ...
            implementation(files("../libs/myLib-release.aar"))
        }
        commonMain.dependencies {
            ...
            //implementation(project(":myLib"))
            implementation(files("../libs/myLib-metadata.jar"))
        }
        jsMain.dependencies {
            ...
            implementation(files("../libs/myLib-js.klib"))
        }
    }
}

Problem

I successfully retrieve and import my lib on androidMain and jsMain. However, I can't import it in my commonMain code. My lib namespace is found, but I can't use the defined class in it.

I checked the generated .jar, and it seems everything is here. (Also, when I import it from the module project as implementation(project(":myLib")), everything works fine)

Is there a thing I'm missing here ? Anyone as an idea why I can't do that ?

I have a problem importing my kmp lib to my sample project.

Project

I have the following code structure :

├── app/ (KMP App module containing my samples apps)
│   ├── commonMain/
│   ├── androidMain/
│   └── jsMain/
├── myLib/ (KMP module for my library)
│   └── commonMain/
└── libs/ (myLib compiled as files)
    ├── myLib-release.aar
    ├── myLib-metadata.jar
    └── myLib-js.klib

Steps

What I try to do is building myLib to files and importing it in the commonMain folder of my samples app (to access it from commonMain, jsMain & androidMain).

1. I build myLib. Here is my myLib/build.gradle file :

plugins {
    alias(libs.plugins.kotlinMultiplatform)
    alias(libs.plugins.android.library)
}

val sdkVersion = "1.2.0"

kotlin {
    androidTarget {
        version = sdkVersion

        @OptIn(ExperimentalKotlinGradlePluginApi::class)
        compilerOptions {
            jvmTarget.set(JvmTarget.JVM_21)
        }
    }
    js {
        browser {
            version = sdkVersion
            binaries.executable()
        }
    }
    withSourcesJar()

    sourceSets {
        commonMain {
            dependencies {
                ...
            }
        }
    }
}

android {...}
dependencies {...}

tasks.withType<Jar> {
    manifest {
        attributes["Implementation-Title"] = "myLib-${sdkVersion}"
        attributes["Implementation-Version"] = sdkVersion
    }
}

2. I retrieve the generated files in the ./myLib/build/ folder and extract them to ./libs/

3. I import them in my sample module. Here is the app/build.gradle :

kotlin {
    androidTarget {...}

    js {...}

    sourceSets {
        androidMain.dependencies {
            ...
            implementation(files("../libs/myLib-release.aar"))
        }
        commonMain.dependencies {
            ...
            //implementation(project(":myLib"))
            implementation(files("../libs/myLib-metadata.jar"))
        }
        jsMain.dependencies {
            ...
            implementation(files("../libs/myLib-js.klib"))
        }
    }
}

Problem

I successfully retrieve and import my lib on androidMain and jsMain. However, I can't import it in my commonMain code. My lib namespace is found, but I can't use the defined class in it.

I checked the generated .jar, and it seems everything is here. (Also, when I import it from the module project as implementation(project(":myLib")), everything works fine)

Is there a thing I'm missing here ? Anyone as an idea why I can't do that ?

• kotlin
• kotlin-multiplatform
• gradle-kotlin-dsl
• kmp

1 Answer 1

Your common code needs more than just the common metadata to work. There is not yet¹ a common format which you can pass around in one simple file like that.

The way to pass multiplatform libraries around is as published "components", which is your compiled code artifacts together with metadata which tells the multiplatform compilation where to find the platform-specific artifacts that it needs.

To do this, you should publish your library, at first either to your Maven local repository or even just a local directory acting as a repository. Your consuming build can then obtain your publication from your repository using its coordinates, just like a regular third-party library. Kotlin have written a guide on multiplatform publishing to get you started.

Alternatively, depending on what you are doing you may consider working with the library as a subproject within your app, making it a Gradle multi-module project. This allows you to easily pass around subprojects as libraries without the configuration publishing involves.

¹ See Kotlin issue KT-52666