Gradle Kotlin DSL multi project build with Java Modules - gradle

Question

I'm creating a new project (using IntelliJ IDEA) that will be using:
Gradle as the build system
Kotlin DSL for build scripts
Java 9 modules for "organisation"
Kotlin as the primary language
I'm having problems setting up Gradle to properly build my project. Most examples I've found are for Groovy and not Kotlin DSL, and most only cover some of the features I want, but not all.
Right now I have two modules, core and lib, where the core module requires the lib module. My gradle build scripts are:
build.gradle.kts
plugins {
base
kotlin("jvm") version "1.3.41" apply false
}
subprojects {
afterEvaluate {
tasks.withType<JavaCompile> {
inputs.property("moduleName", extra["moduleName"])
options.compilerArgs.addAll(arrayOf("--module-path", classpath.asPath))
classpath = files()
}
}
repositories {
mavenCentral()
jcenter()
}
}
core/build.gradle.kts
extra.set("moduleName", "myproject.core")
plugins {
kotlin("jvm")
}
dependencies {
compile(kotlin("stdlib"))
compile(project(":networking"))
}
lib/build.gradle.kts
extra.set("moduleName", "myproject.lib")
plugins {
kotlin("jvm")
}
dependencies {
compile(kotlin("stdlib"))
}
Doing this, configuration fails with:
A problem occurred configuring project ':core'.
Cannot get property 'moduleName' on extra properties extension as it does not exist
If I remove the inputs.property() line the configuration succeeds, but the core compilation fails (lib compiles successfully) with :
Task :core:compileKotlin
e: Module myproject.lib cannot be found in the module graph
I assume the issue is is my root build.gradle.kts, but I cannot figure out how to make it work. Googling around, Kotlin DSL for Gradle is somewhat new and not as widely used, and documentation is pretty scarce.
Any advice would be appreciated!

Answer 1

Naturally after posting the question I found the solution. There exists a Gradle plugin that does exactly what's needed in this situation, with a KotlinDSL example: https://github.com/java9-modularity/gradle-modules-plugin/tree/master/test-project-kotlin
Using the plugin, all I needed to do is change the root build.gradle.kts file:
plugins {
base
kotlin("jvm") version "1.3.41" apply false
id("org.javamodularity.moduleplugin") version "1.5.0" apply false
}
subprojects {
apply(plugin = "org.javamodularity.moduleplugin")
repositories {
mavenCentral()
jcenter()
}
}
Note: Make sure that your module-info.java file is in the java src folder, and not in the kotlin src folder, otherwise the plugin will not detect the module.