Fix Gradle 9 compatibility: upgrade nexus plugin, fix deprecated APIs

- Upgrade io.github.gradle-nexus.publish-plugin from 1.3.0 to 2.0.0
  (fixes ClassNotFoundException for DefaultDecoratedConvention removed in Gradle 9)
- Rename closeAndReleaseStagingRepository to closeAndReleaseStagingRepositories
  (breaking change in nexus plugin 2.0.0)
- Replace deprecated KotlinCompilerVersion with version-less kotlin() dependency
- Migrate kotlinOptions DSL to compilerOptions DSL (deprecated in Kotlin 2.3.10)
- Replace -Xopt-in with -opt-in compiler flag
- Replace deprecated String.toLowerCase() with lowercase()
- Replace deprecated buildDir with layout.buildDirectory
- Add junit-platform-launcher dependency (required by Gradle 9)

Co-authored-by: jGleitz <4305652+jGleitz@users.noreply.github.com>

Author: Copilot

base/build.gradle.kts

@@ -1,6 +1,5 @@
 import org.gradle.api.JavaVersion.VERSION_17
-import org.jetbrains.kotlin.config.KotlinCompilerVersion
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
 	kotlin("jvm")
@@ -16,9 +15,10 @@ dependencies {
 	testImplementation(name = "spek-dsl-jvm", version = spekVersion, group = "org.spekframework.spek2")
 	testImplementation(name = "atrium-fluent-en_GB", version = "0.16.0", group = "ch.tutteli.atrium")
 	testRuntimeOnly(name = "spek-runner-junit5", version = spekVersion, group = "org.spekframework.spek2")
+	testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 
 	constraints {
-		testImplementation(kotlin("reflect", version = KotlinCompilerVersion.VERSION))
+		testImplementation(kotlin("reflect"))
 	}
 }
 
@@ -29,23 +29,20 @@ java {
 
 kotlin {
 	explicitApi()
-}
-
-tasks.withType<KotlinCompile> {
-	kotlinOptions {
-		jvmTarget = "17"
-		freeCompilerArgs += "-Xopt-in=kotlin.io.path.ExperimentalPathApi"
+	compilerOptions {
+		jvmTarget = JvmTarget.JVM_17
+		freeCompilerArgs.add("-opt-in=kotlin.io.path.ExperimentalPathApi")
 	}
 }
 
 tasks.withType<Test> {
 	useJUnitPlatform()
 
-	val testPwd = buildDir.resolve("test-pwd")
+	val testPwd = layout.buildDirectory.dir("test-pwd")
 	doFirst {
-		testPwd.mkdirs()
+		testPwd.get().asFile.mkdirs()
 	}
-	workingDir = testPwd
+	workingDir = testPwd.get().asFile
 }
 
 

base/src/main/kotlin/DefaultTestFiles.kt

@@ -159,7 +159,7 @@ public class DefaultTestFiles: TestFiles {
 		private val unixInvalidCharacters get() = Regex("[/\u0000]")
 		private val windowsInvalidCharacters get() = Regex("[/\\\\<>:\"|?*\u0000]")
 		private val invalidFileNameCharacters by lazy(PUBLICATION) {
-			val osName = System.getProperty("os.name").toLowerCase()
+			val osName = System.getProperty("os.name").lowercase()
 			if (setOf("nix", "nux", "aix", "mac").any { osName.contains(it) }) unixInvalidCharacters
 			else windowsInvalidCharacters // default to windows because it is the most restrictive
 		}

build.gradle.kts

@@ -6,7 +6,7 @@ plugins {
 	id("org.jetbrains.dokka-javadoc") version "2.1.0" apply false
 	`maven-publish`
 	signing
-	id("io.github.gradle-nexus.publish-plugin") version "1.3.0"
+	id("io.github.gradle-nexus.publish-plugin") version "2.0.0"
 	idea
 }
 
@@ -150,10 +150,10 @@ subprojects {
 		tasks.register("release") {
 			group = "release"
 			description = "Releases the project to all remote repositories"
-			dependsOn(publishToGithub, publishToMavenCentral, rootProject.tasks.closeAndReleaseStagingRepository)
+			dependsOn(publishToGithub, publishToMavenCentral, rootProject.tasks.closeAndReleaseStagingRepositories)
 		}
 
-		rootProject.tasks.closeAndReleaseStagingRepository { mustRunAfter(publishToMavenCentral) }
+		rootProject.tasks.closeAndReleaseStagingRepositories { mustRunAfter(publishToMavenCentral) }
 	}
 }
 

kotest/build.gradle.kts

@@ -1,6 +1,5 @@
 import org.gradle.api.JavaVersion.VERSION_17
-import org.jetbrains.kotlin.config.KotlinCompilerVersion
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
 	kotlin("jvm")
@@ -19,9 +18,10 @@ dependencies {
 
 	testImplementation(name = "kotest-runner-junit5", version = kotestVersion, group = "io.kotest")
 	testImplementation(name = "atrium-fluent-en_GB", version = "0.16.0", group = "ch.tutteli.atrium")
+	testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 
 	constraints {
-		testImplementation(kotlin("reflect", version = KotlinCompilerVersion.VERSION))
+		testImplementation(kotlin("reflect"))
 	}
 }
 
@@ -32,17 +32,14 @@ java {
 
 kotlin {
 	explicitApi()
-}
-
-tasks.withType<KotlinCompile> {
-	kotlinOptions {
-		jvmTarget = "17"
+	compilerOptions {
+		jvmTarget = JvmTarget.JVM_17
 	}
 }
 
 tasks.compileTestKotlin {
-	kotlinOptions {
-		freeCompilerArgs += "-Xopt-in=kotlin.io.path.ExperimentalPathApi"
+	compilerOptions {
+		freeCompilerArgs.add("-opt-in=kotlin.io.path.ExperimentalPathApi")
 	}
 }
 

spek/build.gradle.kts

@@ -1,6 +1,5 @@
 import org.gradle.api.JavaVersion.VERSION_17
-import org.jetbrains.kotlin.config.KotlinCompilerVersion
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
 	kotlin("jvm")
@@ -21,9 +20,10 @@ dependencies {
 	testImplementation(name = "spek-dsl-jvm", version = spekVersion, group = "org.spekframework.spek2")
 	testImplementation(name = "atrium-fluent-en_GB", version = "0.16.0", group = "ch.tutteli.atrium")
 	testRuntimeOnly(name = "spek-runner-junit5", version = spekVersion, group = "org.spekframework.spek2")
+	testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 
 	constraints {
-		testImplementation(kotlin("reflect", version = KotlinCompilerVersion.VERSION))
+		testImplementation(kotlin("reflect"))
 	}
 }
 
@@ -34,17 +34,14 @@ java {
 
 kotlin {
 	explicitApi()
-}
-
-tasks.withType<KotlinCompile> {
-	kotlinOptions {
-		jvmTarget = "17"
+	compilerOptions {
+		jvmTarget = JvmTarget.JVM_17
 	}
 }
 
 tasks.compileTestKotlin {
-	kotlinOptions {
-		freeCompilerArgs += "-Xopt-in=kotlin.io.path.ExperimentalPathApi"
+	compilerOptions {
+		freeCompilerArgs.add("-opt-in=kotlin.io.path.ExperimentalPathApi")
 	}
 }