Multi-Release for Class-File API

Author: Goooler

build.gradle.kts

@@ -7,6 +7,7 @@ import org.gradle.api.plugins.JavaPlugin.SOURCES_ELEMENTS_CONFIGURATION_NAME
 import org.gradle.plugin.compatibility.compatibility
 import org.jetbrains.kotlin.gradle.dsl.JvmDefaultMode
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.dsl.KotlinJvmCompilerOptions
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.dsl.abi.ExperimentalAbiValidation
 
@@ -30,7 +31,7 @@ dokka { dokkaPublications.html { outputDirectory = rootDir.resolve("docs/api") }
 kotlin {
   explicitApi()
   @OptIn(ExperimentalAbiValidation::class) abiValidation { enabled = true }
-  val jdkRelease = "24"
+  val jdkRelease = "17"
   compilerOptions {
     allWarningsAsErrors = true
     // https://docs.gradle.org/current/userguide/compatibility.html#kotlin
@@ -45,6 +46,8 @@ kotlin {
   }
 }
 
+addMultiReleaseSourceSet(24)
+
 lint {
   baseline = file("gradle/lint-baseline.xml")
   ignoreTestFixturesSources = true
@@ -222,6 +225,8 @@ kotlin.target.compilations {
   }
 }
 
+tasks.jar { manifest.attributes("Multi-Release" to true) }
+
 tasks.pluginUnderTestMetadata { pluginClasspath.from(testPluginClasspath) }
 
 tasks.check { dependsOn(tasks.withType<Test>()) }
@@ -236,3 +241,21 @@ tasks.clean {
       rootDir.resolve("site"),
     )
 }
+
+fun addMultiReleaseSourceSet(version: Int) {
+  kotlin.target.compilations.create("java${version}") {
+    associateWith(kotlin.target.compilations.getByName("main"))
+    compileTaskProvider {
+      compilerOptions {
+        this@compilerOptions as KotlinJvmCompilerOptions
+        jvmTarget = JvmTarget.fromTarget(version.toString())
+        freeCompilerArgs.add("-Xjdk-release=$version")
+      }
+    }
+    compileJavaTaskProvider { options.release = version }
+
+    tasks.jar { from(output.allOutputs) { into("META-INF/versions/$version") } }
+
+    tasks.withType<Test>().configureEach { inputs.files(output.allOutputs) }
+  }
+}

gradle.properties

@@ -2,6 +2,11 @@
 # https://kotlinlang.org/docs/gradle-configure-project.html#dependency-on-the-standard-library
 kotlin.stdlib.default.dependency=false
 
+# Keep associated Kotlin compilations from depending on archive tasks (e.g., jar), which can create circular task graphs in multi-release setups.
+# https://kotlinlang.org/docs/gradle-configure-project.html//disable-use-of-artifact-in-compilation-task
+# https://kotlinlang.org/docs/whatsnew2020.html#added-task-dependency-for-rare-cases-when-the-compile-task-lacks-one-on-an-artifact
+kotlin.build.archivesTaskOutputAsFriendModule=false
+
 org.gradle.caching=true
 org.gradle.configuration-cache=true
 org.gradle.configuration-cache.parallel=true