Unresolved reference: compileKotlin in build.gradle.kts - gradle

Question

Kotlin project success build by build.gradle:
compileKotlin {
kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8
}
compileTestKotlin {
kotlinOptions.jvmTarget = JavaVersion.VERSION_1_8
}
Nice.
But I need to change to build.gradle.kts:
plugins {
kotlin("jvm") version "1.2.10"
id("application")
}
group = "com.myproject"
version = "1.0-SNAPSHOT"
application {
mainClassName = "MainKt"
}
java.sourceCompatibility = JavaVersion.VERSION_1_8
repositories {
mavenCentral()
jcenter()
}
val kotlinVer = "1.2.10"
dependencies {
compile(kotlin(module = "stdlib-jre8", version = kotlinVer))
implementation("com.google.code.gson:gson:2.7")
implementation("com.squareup.okhttp3:logging-interceptor:3.8.0")
implementation("com.squareup.retrofit2:converter-gson:2.1.0")
implementation("com.squareup.retrofit2:retrofit:2.5.0")
implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
}
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
and now I get error:
Line 32: compileKotlin {
^ Unresolved reference: compileKotlin

Answer 1

There's an issue in the Kotlin Gradle DSL that causes this.
https://github.com/gradle/kotlin-dsl-samples/issues/1368
You will need to use the following workaround until it gets resolved.
tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
kotlinOptions {
jvmTarget = "1.8"
}
}

Answer 2

Following official Kotlin documentation (using Gradle part), I suggest to use such constructions in the build.gradle.kts:
import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
plugins {
java
kotlin("jvm") version ("1.3.21")
}
// repositories, dependencies, etc...
val compileKotlin: KotlinCompile by tasks
val compileTestKotlin: KotlinCompile by tasks
compileKotlin.kotlinOptions {
jvmTarget = "1.8"
}
compileTestKotlin.kotlinOptions {
jvmTarget = "1.8"
}

Answer 3

Use withType keyword:
import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
plugins {
val kotlin = "1.3.61"
kotlin("jvm") version kotlin apply false
}
subprojects {
repositories { mavenCentral(); mavenLocal() }
apply(plugin = "org.jetbrains.kotlin.jvm")
tasks {
val java: String by project
withType<KotlinCompile>{
kotlinOptions { jvmTarget = java }; sourceCompatibility = java; targetCompatibility = java
}
}
}