Apply atomicfu compiler plugin directly in buildscript classpath.

README.md

@@ -107,10 +107,15 @@ operations. They can be also atomically modified via `+=` and `-=` operators.
 
 Gradle configuration is supported for all platforms, minimal version is Gradle 6.8.
 
-In top-level build file:
+To apply kotlinx-atomicfu plugin, you need to add 2 dependencies to the project classpath:
+1. `atomicfu-gradle-plugin`: it provides the necessary library dependencies and manages transformation modes.
+2. `atomicfu` compiler plugin: the compiler plugin is used to perform IR transformations (see [Atomicfu compiler plugin](#atomicfu-compiler-plugin) section).
+
+> Note: kotlinx-atomicfu gradle plugin does not have an id and is not currently published to the Gradle Plugin Portal. 
+> Therefore, the only available method for application is through the buildscript specification.
 
 <details open>
-<summary>Kotlin</summary>
+<summary>Kotlin DSL</summary>
 
 ```kotlin
 buildscript {
@@ -120,6 +125,9 @@ buildscript {
 
     dependencies {
       classpath("org.jetbrains.kotlinx:atomicfu-gradle-plugin:0.23.1")
+      // Please note that the Kotlin version specified for the atomicfu compiler plugin 
+      // should match the Kotlin version used in your project.
+      classpath("org.jetbrains.kotlin:atomicfu:$kotlin_version")
     }
 }
 
@@ -128,7 +136,7 @@ apply(plugin = "kotlinx-atomicfu")
 </details>
 
 <details>
-<summary>Groovy</summary>
+<summary>Groovy DSL</summary>
 
 ```groovy
 buildscript {
@@ -137,6 +145,9 @@ buildscript {
     }
     dependencies {
         classpath 'org.jetbrains.kotlinx:atomicfu-gradle-plugin:0.23.1'
+        // Please note that the Kotlin version specified for the atomicfu compiler plugin 
+        // should match the Kotlin version used in your project.
+        classpath 'org.jetbrains.kotlin:atomicfu:$kotlin_version'
     }
 }
 

atomicfu-gradle-plugin/build.gradle

@@ -23,7 +23,7 @@ dependencies {
     compileOnly "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     // Atomicfu compiler plugin dependency will be loaded to kotlinCompilerPluginClasspath
     // Atomicfu plugin will only be applied if the flag is set kotlinx.atomicfu.enableJsIrTransformation=true
-    implementation "org.jetbrains.kotlin:atomicfu:$kotlin_version"
+    compileOnly "org.jetbrains.kotlin:atomicfu:$kotlin_version"
 
     testImplementation gradleTestKit()
     testImplementation 'org.jetbrains.kotlin:kotlin-test'

atomicfu-gradle-plugin/src/main/kotlin/kotlinx/atomicfu/plugin/gradle/AtomicFUGradlePlugin.kt

@@ -45,12 +45,42 @@ open class AtomicFUGradlePlugin : Plugin<Project> {
         val pluginVersion = rootProject.buildscript.configurations.findByName("classpath")
             ?.allDependencies?.find { it.name == "atomicfu-gradle-plugin" }?.version
         extensions.add(EXTENSION_NAME, AtomicFUPluginExtension(pluginVersion))
+        checkClasspathForAtomicfuCompilerPlugin(pluginVersion)
         applyAtomicfuCompilerPlugin()
         configureDependencies()
         configureTasks()
     }
 }
 
+private fun Project.checkClasspathForAtomicfuCompilerPlugin(pluginVersion: String?) {
+    val kotlinVersion = getKotlinPluginVersion()
+    rootProject.buildscript.configurations.findByName("classpath")
+        ?.allDependencies?.find { it.group == "org.jetbrains.kotlin" && it.name == "atomicfu" }?.let { 
+            require(it.version == kotlinVersion) {
+                "Please ensure that the Kotlin version specified for the atomicfu compiler plugin matches the Kotlin version used in your project. \n" +
+                "You should use this dependency in your classpath: classpath(\"org.jetbrains.kotlin:atomicfu:$kotlinVersion\")\n\n" +
+                "For details about plugin application, please refer to the README section at: https://github.com/Kotlin/kotlinx-atomicfu/blob/master/README.md#apply-plugin"
+            }
+        }
+        ?: error("Please add a dependency to the atomicfu compiler plugin in the buildscript classpath configuration, " + 
+            "in addition to the atomicfu-gradle-plugin dependency:\n" +
+            "```\n" +    
+            "buildscript {\n" +
+            "    repositories {\n" +
+            "        mavenCentral() \n" +
+            "    }\n" +
+            "\n" +
+            "    dependencies {\n" +
+            "        classpath(\"org.jetbrains.kotlinx:atomicfu-gradle-plugin:$pluginVersion\")\n" +
+            "        classpath(\"org.jetbrains.kotlin:atomicfu:$kotlinVersion\")\n" +
+            "    }\n" +
+            "}\n\n" + 
+            "apply(plugin = \"kotlinx-atomicfu\")\n" +
+            "```\n\n" +
+            "For details about plugin application, please refer to the README section at: https://github.com/Kotlin/kotlinx-atomicfu/blob/master/README.md#apply-plugin"            
+        )
+}
+
 private fun Project.checkCompatibility() {
     val currentGradleVersion = GradleVersion.current()
     val kotlinVersion = getKotlinVersion()
@@ -204,8 +234,6 @@ private fun Project.addJsCompilerPluginRuntimeDependency() {
                         if (getKotlinVersion().atLeast(1, 7, 10)) {
                             // since Kotlin 1.7.10 `kotlinx-atomicfu-runtime` is published and should be added directly
                             implementation("org.jetbrains.kotlin:kotlinx-atomicfu-runtime:${getKotlinPluginVersion()}")
-                        } else {
-                            implementation("org.jetbrains.kotlin:atomicfu:${getKotlinPluginVersion()}")
                         }
                     }
                 }