Kotlin 1.9.20. Disable k2 due to failing tests. Java 21 toolchain.

build.gradle.kts

@@ -1,8 +1,7 @@
 import com.google.cloud.tools.jib.gradle.BuildImageTask
 import com.netflix.graphql.dgs.codegen.gradle.GenerateJavaTask
 import io.gitlab.arturbosch.detekt.Detekt
-import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 plugins {
     alias(libs.plugins.kotlin.jvm)
@@ -58,9 +57,30 @@ dependencies {
 
 kotlin {
     jvmToolchain {
-        languageVersion.set(JavaLanguageVersion.of(20))
+        languageVersion.set(JavaLanguageVersion.of(21))
         vendor.set(JvmVendorSpec.AZUL)
     }
+    compilerOptions {
+        // languageVersion.set(KotlinVersion.KOTLIN_2_0) TODO enable once tests pass with K2
+        freeCompilerArgs.addAll(
+            "-opt-in=kotlin.RequiresOptIn",
+            "-Xjsr305=strict",
+            "-Xcontext-receivers",
+        )
+    }
+}
+
+tasks.withType<Test>().configureEach {
+    useJUnitPlatform()
+    maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).coerceAtLeast(1)
+}
+
+configurations.configureEach {
+    resolutionStrategy.eachDependency {
+        if (this@configureEach.name == "detekt" && requested.group == "org.jetbrains.kotlin") {
+            useVersion("1.9.10")
+        }
+    }
 }
 
 allprojects {
@@ -72,29 +92,13 @@ allprojects {
     }
     tasks.withType<Detekt>().configureEach {
         reports {
+            jvmTarget = JvmTarget.JVM_20.target // TODO remove once detekt supports JVM 21 bytecode
             html.outputLocation.set(file("build/reports/detekt/${project.name}.html"))
         }
     }
     dependencies.add("detektPlugins", libs.detektFormatting)
 }
 
-tasks.withType<KotlinCompile>().configureEach {
-    compilerOptions {
-        languageVersion.set(KotlinVersion.KOTLIN_2_0)
-        freeCompilerArgs.addAll(
-            "-opt-in=kotlin.RequiresOptIn",
-            "-Xjsr305=strict",
-            "-Xcontext-receivers",
-            "-Xbackend-threads=0",
-        )
-    }
-}
-
-tasks.withType<Test>().configureEach {
-    useJUnitPlatform()
-    maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).coerceAtLeast(1)
-}
-
 fun Project.envOrProp(name: String): String {
     return providers.environmentVariable(name).orNull
         ?: providers.gradleProperty(name).orNull

gradle.properties

@@ -7,4 +7,3 @@ org.gradle.configuration-cache-problems=warn
 
 # Kotlin code style
 kotlin.code.style=official
-kotlin.experimental.tryK2=true

gradle/libs.versions.toml

@@ -1,13 +1,11 @@
 [versions]
-kotlin = "1.9.10"
+kotlin = "1.9.20"
 spring-boot = "3.1.5"
 spring-dependencyManagement = "1.1.3"
 jib = "3.4.0"
 ktor = "2.3.6"
 dgsBom = "8.0.1"
 dgsCodegen = "6.0.3"
-kotlinx-coroutines = "1.7.2"
-kotlinx-serialization = "1.5.1"
 detekt = "1.23.3"
 apacheCommonsText = "1.10.0"
 caffeine = "3.1.8"