Fat Jar expands dependencies with Gradle Kotlin DSL - gradle

Question

I am trying to build a fat jar using the following in my Kotlin based gradle file.
val fatJar = task("fatJar", type = Jar::class) {
baseName = "safescape-lib-${project.name}"
// manifest Main-Class attribute is optional.
// (Used only to provide default main class for executable jar)
from(configurations.runtimeClasspath.map({ if (it.isDirectory) it else zipTree(it) }))
with(tasks["jar"] as CopySpec)
}
tasks {
"build" {
dependsOn(fatJar)
}
}
However, the fat jar has all the dependencies expanded out. I would like to have the jars included as is in a /lib directory but I cannot work out how to achieve this.
Can anyone give any pointers as to how I can achieve this?
Thanks

Answer 1

Well you are using zipTree in that map part of the spec, and it behaves according to the documentation: it unzips the files that are not a directory.
If you want the jars in /lib, replace your from with:
from(configurations.runtimeClasspath) {
into("lib")
}

Answer 2

In case anyone is using kotlin-multiplatform plugin, the configuration is a bit different. Here's a fatJar task configuration assuming JVM application with embedded JS frontend from JS module:
afterEvaluate {
tasks {
create("jar", Jar::class).apply {
dependsOn("jvmMainClasses", "jsJar")
group = "jar"
manifest {
attributes(
mapOf(
"Implementation-Title" to rootProject.name,
"Implementation-Version" to rootProject.version,
"Timestamp" to System.currentTimeMillis(),
"Main-Class" to mainClassName
)
)
}
val dependencies = configurations["jvmRuntimeClasspath"].filter { it.name.endsWith(".jar") } +
project.tasks["jvmJar"].outputs.files +
project.tasks["jsJar"].outputs.files
dependencies.forEach { from(zipTree(it)) }
into("/lib")
}
}
}