ViaBackwards/universal/build.gradle.kts

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

plugins {
    id("com.github.johnrengelman.shadow")
}

val platforms = setOf(
        projects.viabackwardsBukkit,
        projects.viabackwardsBungee,
        projects.viabackwardsFabric,
        projects.viabackwardsSponge,
        projects.viabackwardsVelocity
).map { it.dependencyProject }

tasks {
    shadowJar {
        archiveClassifier.set("")
        archiveFileName.set("ViaBackwards-${project.version}.jar")
        destinationDirectory.set(rootProject.projectDir.resolve("build/libs"))
        duplicatesStrategy = DuplicatesStrategy.EXCLUDE
        platforms.forEach { platform ->
            val shadowJarTask = platform.tasks.getByName("shadowJar", ShadowJar::class)
            dependsOn(shadowJarTask)
            dependsOn(platform.tasks.withType<Jar>())
            from(zipTree(shadowJarTask.archiveFile))
        }
    }
    build {
        dependsOn(shadowJar)
    }
    sourcesJar {
        rootProject.subprojects.forEach { subproject ->
            if (subproject == project) return@forEach
            val platformSourcesJarTask = subproject.tasks.findByName("sourcesJar") as? Jar ?: return@forEach
            dependsOn(platformSourcesJarTask)
            from(zipTree(platformSourcesJarTask.archiveFile))
        }
    }
}

publishShadowJar()