Kotlin-multiplatform: ShadowJar gradle plugin creates empty jar

Question

I tried to use ShadowJar gradle pluging to pack my ktor app into fat jar. But as result of shadowJar task i get every time almost empty jar. It contains only manifest (main class is properly set).

Gradle configuration (groovy):

import org.gradle.jvm.tasks.Jar

buildscript {
    ext.kotlin_version = '1.3.72'
    ext.ktor_version = '1.3.2'
    ext.serialization_version = '0.20.0'
    ext.sl4j_version = '1.6.1'
    repositories { jcenter() }

    dependencies {
        classpath 'com.github.jengelman.gradle.plugins:shadow:5.2.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath "org.jetbrains.kotlin:kotlin-serialization:$kotlin_version"
    }
}

plugins {
    id 'org.jetbrains.kotlin.multiplatform' version '1.3.61'
}

apply plugin: 'kotlinx-serialization'
apply plugin: 'application'
apply plugin: 'java'

mainClassName = 'com.example.JvmMainKt'

apply plugin: 'com.github.johnrengelman.shadow'

repositories {
    mavenCentral()
    jcenter()
}
group 'com.example'
version '0.0.1'

apply plugin: 'maven-publish'

kotlin {

    jvm {
    }
    js {
        browser {
        }
        nodejs {
        }
    }
    // For ARM, should be changed to iosArm32 or iosArm64
    // For Linux, should be changed to e.g. linuxX64
    // For MacOS, should be changed to e.g. macosX64
    // For Windows, should be changed to e.g. mingwX64
    mingwX64("mingw") {
        binaries {
            executable {
                // Change to specify fully qualified name of your application's entry point:
                entryPoint = 'main'
                // Specify command-line arguments, if necessary:
                runTask?.args('')
            }
        }
    }
    sourceSets {
        commonMain {
            dependencies {
                implementation kotlin('stdlib-common')
                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-common:$serialization_version"
                implementation "io.ktor:ktor-client-core:$ktor_version"
            }
        }
        commonTest {
            dependencies {
                implementation kotlin('test-common')
                implementation kotlin('test-annotations-common')
            }
        }
        jvmMain {
            dependencies {
                implementation kotlin('stdlib-jdk8')
                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:$serialization_version"
                implementation "io.ktor:ktor-serialization:$ktor_version"
                implementation "io.ktor:ktor-server-netty:$ktor_version"
                implementation "org.slf4j:slf4j-simple:$sl4j_version"

            }
        }
        jvmTest {
            dependencies {
                implementation kotlin('test')
                implementation kotlin('test-junit')
            }
        }
        jsMain {
            dependencies {
                implementation kotlin('stdlib-js')
                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-js:$serialization_version"
            }
        }
        jsTest {
            dependencies {
                implementation kotlin('test-js')
            }
        }
        mingwMain {
            dependencies {
                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-native:$serialization_version"
            }
        }
        mingwTest {
        }
    }
}

shadowJar {
    mainClassName = 'com.example.JvmMainKt'

    mergeServiceFiles()
}

Answer 1

I finally found solution to my problem.

import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar

//...

task shadowJar2(type: ShadowJar) {
    def target = kotlin.targets.jvm
    from target.compilations.main.output
    def runtimeClasspath = target.compilations.main.runtimeDependencyFiles
    manifest {
        attributes 'Main-Class': mainClassName
    }
    configurations = [runtimeClasspath]
}