Cannot use application plugin in Gradle with Kotlin

Question

I am trying to configure ktor server using gradle, but I am having issues with the application config and I cannot understand what is going on as I am doing nothing wrong according to the docs and other examples I found online.

Here is my build.gradle.kts:

plugins {
    kotlin("jvm") version "1.7.0"
    kotlin("plugin.serialization") version "1.7.0"
    application {
        mainClass.set("ApplicationKt")
    }
}

repositories {
    mavenCentral()
}

tasks.withType<KotlinCompile> {
    kotlinOptions.jvmTarget = "17"
}

The error I get is:

Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: 
public inline operator fun <T : Any, C : NamedDomainObjectContainer<TypeVariable(T)>> TypeVariable(C).invoke(configuration: Action<NamedDomainObjectContainerScope<TypeVariable(T)>>): TypeVariable(C) defined in org.gradle.kotlin.dsl
public operator fun <T> Closure<TypeVariable(T)>.invoke(): TypeVariable(T) defined in org.gradle.kotlin.dsl
public operator fun <T> Closure<TypeVariable(T)>.invoke(x: Any?): TypeVariable(T) defined in org.gradle.kotlin.dsl
public operator fun <T> Closure<TypeVariable(T)>.invoke(vararg xs: Any?): TypeVariable(T) defined in org.gradle.kotlin.dsl
public operator fun <V> Callable<TypeVariable(V)>.invoke(): TypeVariable(V) defined in org.gradle.kotlin.dsl
public operator fun <T, R> DeepRecursiveFunction<TypeVariable(T), TypeVariable(R)>.invoke(value: TypeVariable(T)): TypeVariable(R) defined in kotlin
public operator fun <T> Action<in TypeVariable(T)>.invoke(target: TypeVariable(T)): Unit defined in org.gradle.kotlin.dsl
public operator fun <T> NamedDomainObjectProvider<TypeVariable(T)>.invoke(action: TypeVariable(T).() -> Unit): Unit defined in org.gradle.kotlin.dsl
public operator fun ArtifactHandler.invoke(configuration: ArtifactHandlerScope.() -> Unit): Unit defined in org.gradle.kotlin.dsl
public operator fun DependencyConstraintHandler.invoke(configuration: DependencyConstraintHandlerScope.() -> Unit): Unit defined in org.gradle.kotlin.dsl
public inline operator fun <T> ExtraPropertiesExtension.invoke(initialValueProvider: () -> TypeVariable(T)): InitialValueExtraPropertyDelegateProvider<TypeVariable(T)> defined in org.gradle.kotlin.dsl
public operator fun <T> ExtraPropertiesExtension.invoke(initialValue: TypeVariable(T)): InitialValueExtraPropertyDelegateProvider<TypeVariable(T)> defined in org.gradle.kotlin.dsl
public operator fun <T> Spec<TypeVariable(T)>.invoke(arg: TypeVariable(T)): Boolean defined in org.gradle.kotlin.dsl
public inline operator fun TaskContainer.invoke(configuration: TaskContainerScope.() -> Unit): TaskContainer defined in org.gradle.kotlin.dsl

Also, if I specify the application plugin without any body it is all okay. But with the configuration body IntelliJ fails to import the plugin... not sure if this is some issue with IntelliJ or not, but I guess it was worth mentioning.

Any help is appreciated.

Answer 1

You should write the application plugin configuration outside of plugins block:

plugins {
    ...
    application
}

...

application {
    mainClass.set("com.example.MainKt")
}

See examples in the official documentation .

Answer 2

You're trying to configure the plugin at the same point you declare/apply it. You should have:

plugins {
    kotlin("jvm") version "1.7.0"
    kotlin("plugin.serialization") version "1.7.0"
    application // apply plugin
}

// configure plugin
application {
    mainClass.set("ApplicationKt")
}

repositories {
    mavenCentral()
}

tasks.withType<KotlinCompile> {
    kotlinOptions.jvmTarget = "17"
}

IntelliJ may not recognize (re: syntax highlighting, types, etc.) the "configure plugin" part until you refresh the Gradle project.