"Unresolved reference: implementation" by using subprojects in kotlin-gradle

Question

I want to split my project into subprojects. The default Gradle setting from the IntelliJ IDE is:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
    kotlin("jvm") version "1.3.50"
}

group = "project"
version = "0.0.1-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
    implementation(kotlin("stdlib-jdk8"))
}

tasks.withType<KotlinCompile> {
    kotlinOptions.jvmTarget = "1.8"
}

That setting compiles. ButI don't want repeat that code in every subproject. So I changed the build.gradle.kts to

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

subprojects {
    plugins {
        kotlin("jvm") version "1.3.50"
    }

    group = "project"
    version = "0.0.1-SNAPSHOT"

    repositories {
        mavenCentral()
    }

    dependencies {
        implementation(kotlin("stdlib-jdk8"))
    }

    tasks.withType<KotlinCompile> {
        kotlinOptions.jvmTarget = "1.8"
    }
}

but I get the exception:

e: C:[...]\build.gradle.kts:1:12: Unresolved reference: jetbrains e: C:[...]\build.gradle.kts:16:9: Unresolved reference: implementation e: C:[...]\build.gradle.kts:19:20: Unresolved reference: KotlinCompile e: C:[...]\build.gradle.kts:19:35: Type mismatch: inferred type is () -> Unit but Class<TypeVariable(S)!>! was expected e: C:[...]\build.gradle.kts:20:9: Unresolved reference: kotlinOptions

FAILURE: Build failed with an exception.

• Where: Build file 'C:[...]\build.gradle.kts' line: 1

• What went wrong: Script compilation errors:

  Line 01: import org.jetbrains.kotlin.gradle.tasks.KotlinCompile ^ Unresolved reference: jetbrains

  Line 16: implementation(kotlin("stdlib-jdk8")) ^ Unresolved reference: implementation

  Line 19: tasks.withType { ^ Unresolved reference: KotlinCompile

  Line 19: tasks.withType { ^ Type mismatch: inferred type is () -> Unit but Class<TypeVariable(S)!>! was expected

  Line 20: kotlinOptions.jvmTarget = "1.8" ^ Unresolved reference: kotlinOptions

5 errors

• Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 1s

I think there is an easy syntax error, but I can't find it.

Answer 1

Not sure how you're not also getting an error by nesting the plugins { } block under subprojects { } As stated in Limitations of the plugins DSL:

The plugins {} block must also be a top level statement in the buildscript. It cannot be nested inside another construct (e.g. an if-statement or for-loop).

So to fix your issues, move the plugins {} to the top and imperatively apply the plugins in the subprojects {} block:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
    kotlin("jvm") version "1.3.50" apply false
}

subprojects {
    apply {
        plugin("org.jetbrains.kotlin.jvm")
    }

    group = "project"
    version = "0.0.1-SNAPSHOT"

    repositories {
        mavenCentral()
    }

    val implementation by configurations

    dependencies {
        implementation(kotlin("stdlib-jdk8"))
    }

    tasks.withType<KotlinCompile> {
        kotlinOptions.jvmTarget = "1.8"
    }
}

You can read more about the apply false part in the Method details of PluginDependenciesSpec which is the type/scope of the plugins {} block.

You can read more about the val implementation by configurations part in the Understanding what to do when type-safe model accessors are not available

Answer 2

Is important to define the repositories in settings.gradle.kts (project) so that the dependencies of the subprojects are recognized.

settings.gradle.kts (project)

pluginManagement {
    repositories {
        maven("https://dl.bintray.com/kotlin/kotlin-eap")
        mavenCentral()
        maven("https://plugins.gradle.org/m2/")
    }
}
rootProject.name = "project"

include("app")

---

build.gradle.kts (project)

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

        plugins {
            java
            kotlin("jvm") version "1.4-M3" apply false
        }

subprojects {
    apply {
        plugin("org.jetbrains.kotlin.jvm")
    }

    repositories {
        maven("https://dl.bintray.com/kotlin/kotlin-eap")
        mavenCentral()
    }

    val implementation by configurations

    dependencies {
        implementation(kotlin("stdlib-jdk8"))
    }

    tasks.withType<KotlinCompile> {
        kotlinOptions.jvmTarget = "1.8"
    }
}

---

To define plugins for each submodule separately use the lambda apply { plugin("pluginId") }

build.gradle.kts (:app)

apply {
    plugin("org.jetbrains.kotlin.jvm")
}

dependencies {
    implementation(kotlin("stdlib-jdk8"))
}

GL