Publish multiplatform lib to Maven Central, Invalid publication 'js': multiple artifacts with the identical extension and classifier

Multiplatform
1

As Jcenter will be shutdown soon I’m trying to migrate my libs to Maven Central. I have searched a lot to find any working script but with no luck. There is official docs, but they like a joke, there just told to put “maven-publish” plugin to gradle script and voila that’s it.
Currently I’m getting error:

Caused by: org.gradle.api.publish.maven.InvalidMavenPublicationException: Invalid publication 'js': multiple artifacts with the identical extension and classifier ('jar', 'sources').

My script looks like this:

plugins {
    id("kotlin-multiplatform")
    id("org.jetbrains.dokka") version "1.4.0-rc"
    `maven-publish`
    signing
}

kotlin {
    sourceSets {
        jvm()
        js() {
            nodejs()
            browser()
        }
        linuxX64()
        linuxArm64()
        mingwX64()
        macosX64()
        iosArm64()
        iosX64()

        val commonMain by getting {
            dependencies {
            }
        }
        val commonTest by getting {
            dependencies {
                implementation(kotlin("test-common"))
                implementation(kotlin("test-annotations-common"))
            }
        }

        val jsMain by getting {
            dependencies {
            }
        }
        val jsTest by getting {
            dependencies {
                implementation(kotlin("test-js"))
            }
        }

        val jvmMain by getting {
            dependencies {
            }
        }
        val jvmTest by getting {
            dependencies {
                implementation(kotlin("test"))
                implementation(kotlin("test-junit"))
            }
        }

        val nativeMain by creating {
            dependsOn(commonMain)
            dependencies {
            }
        }

        val linuxX64Main by getting {
            dependsOn(nativeMain)
        }
        val linuxArm64Main by getting {
            dependsOn(nativeMain)
        }
        val mingwX64Main by getting {
            dependsOn(nativeMain)
        }
        val macosX64Main by getting {
            dependsOn(nativeMain)
        }
        val iosArm64Main by getting {
            dependsOn(nativeMain)
        }
        val iosX64Main by getting {
            dependsOn(nativeMain)
        }
    }
}

tasks {
    create<Jar>("javadocJar") {
        dependsOn(dokkaJavadoc)
        archiveClassifier.set("javadoc")
        from(dokkaJavadoc.get().outputDirectory)
    }

    dokkaJavadoc {
        println("Dokka !")
        dokkaSourceSets {
            create("commonMain") {
                displayName = "common"
                platform = "common"
            }
        }
    }
}

//  Publishing

val fis = FileInputStream("local.properties")
val properties = Properties().apply {
    load(fis)
}
val ossUser = properties.getProperty("oss.user")
val ossPassword = properties.getProperty("oss.password")
extra["signing.keyId"] = properties.getProperty("signing.keyId")
extra["signing.password"] = properties.getProperty("signing.password")
extra["signing.secretKeyRingFile"] = properties.getProperty("signing.secretKeyRingFile")

val libraryVersion: String by project
val publishedGroupId: String by project
val artifactName: String by project
val libraryName: String by project
val libraryDescription: String by project
val siteUrl: String by project
val gitUrl: String by project
val licenseName: String by project
val licenseUrl: String by project
val developerOrg: String by project
val developerName: String by project
val developerEmail: String by project
val developerId: String by project

project.group = publishedGroupId
project.version = libraryVersion

signing {
    sign(publishing.publications)
}

publishing {
    publications.withType(MavenPublication::class) {
        groupId = publishedGroupId
        artifactId = artifactName
        version = libraryVersion

        artifact(tasks["javadocJar"])
        artifact(tasks["sourcesJar"])

        pom {
            name.set(libraryName)
            description.set(libraryDescription)
            url.set(siteUrl)

            licenses {
                license {
                    name.set(licenseName)
                    url.set(licenseUrl)
                }
            }
            developers {
                developer {
                    id.set(developerId)
                    name.set(developerName)
                    email.set(developerEmail)
                }
            }
            organization {
                name.set(developerOrg)
            }
            scm {
                connection.set(gitUrl)
                developerConnection.set(gitUrl)
                url.set(siteUrl)
            }
        }
    }

    repositories {
        maven("https://oss.sonatype.org/service/local/staging/deploy/maven2/") {
            name = "sonatype"
            credentials {
                username = ossUser
                password = ossPassword
            }
        }
    }
}
2

I figured out. I leave here a link to my answer on stackoverflow