Gradle (Kotlin DSL): "Unresolved reference: proguard" - gradle

Question

Im trying to get Proguard to work but Im still new to Gradle.
My build gradle.kts haves an error (Unresolved reference: proguard), I cant create a proguard Task:
plugins {
id("com.github.johnrengelman.shadow") version "5.2.0"
java
kotlin("jvm") version "1.3.61"
}
group = "*...*"
version = "*...*"
repositories {
mavenCentral()
jcenter()
}
dependencies {
implementation(kotlin("stdlib-jdk8"))
//*...*
implementation("net.sf.proguard","proguard-gradle","6.2.2") //is this correct?
}
configure<JavaPluginConvention> {
sourceCompatibility = JavaVersion.VERSION_1_8
}
tasks {
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
jar{
manifest {
attributes["Main-Class"] = "*...*"
}
}
shadowJar{
archiveBaseName.set("*...*")
archiveClassifier.set("")
archiveVersion.set("")
}
register<proguard.gradle.ProGuardTask>("myProguardTask") { //Unresolved reference: proguard
}
}
This is not an Android Project
Because Stackoverflow wants me to write more than just code: Im planing to somehow link the proguard output to the shadowjar task. If you know how to do it Im also interested to that (and I could not try it myself because of this problem).

Answer 1

You declared a dependency of proguard in project rather than for Gradle itself.
Move the dependency to the buildscript block:
buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'net.sf.proguard:proguard-gradle:6.2.2'
}
}
Then you should be able to create your task.
Alternatively, you can declare the repository in settings.gradle.kts:
pluginManagement {
repositories {
jcenter()
}
}
which will trim down the buildscript block in build.gradle.kts:
buildscript {
dependencies {
classpath("net.sf.proguard:proguard-gradle:6.2.2")
}
}