Expose statically-typed kotlinOptions and compileKotlinTask in DSL

To simplify configuring a `KotlinCompilation` with Gradle Kotlin DSL, it
is essential to expose statically-known types where possible.

This commit parametrizes `KotlinCompilation` with its Kotlin options
type (a subtype of `KotlinCommonOptions`) and adds `kotlinOptions` and
`compileKotlinTask` to `KotlinCompilation`.

(minor) Also reduce the visibility of `attachClassesDir` and
`setupPlugins` to internal, since this API is not for external use.

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/CinteropSettings.kt

@@ -9,9 +9,9 @@ import groovy.lang.Closure
 import org.gradle.api.Action
 import org.gradle.api.Named
 import org.gradle.api.file.FileCollection
-import org.gradle.api.tasks.SourceSetOutput
+import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 
-interface CInteropSettings: Named {
+interface CInteropSettings : Named {
 
     interface IncludeDirectories {
         fun allHeaders(vararg includeDirs: Any)
@@ -22,7 +22,7 @@ interface CInteropSettings: Named {
     }
 
     // TODO: Provide an interface for native compilations.
-    val compilation: KotlinCompilation
+    val compilation: KotlinCompilation<KotlinCommonOptions>
 
     val dependencyConfigurationName: String
     var dependencyFiles: FileCollection

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinCompilation.kt

@@ -9,6 +9,9 @@ import org.gradle.api.Named
 import org.gradle.api.attributes.HasAttributes
 import org.gradle.api.file.ConfigurableFileCollection
 import org.gradle.api.file.FileCollection
+import org.gradle.util.ConfigureUtil
+import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
+import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
 import java.io.File
 
 interface KotlinCompilationOutput {
@@ -19,7 +22,7 @@ interface KotlinCompilationOutput {
     val allOutputs: FileCollection
 }
 
-interface KotlinCompilation: Named, HasAttributes, HasKotlinDependencies {
+interface KotlinCompilation<out T : KotlinCommonOptions> : Named, HasAttributes, HasKotlinDependencies {
     val target: KotlinTarget
 
     val compilationName: String
@@ -36,6 +39,12 @@ interface KotlinCompilation: Named, HasAttributes, HasKotlinDependencies {
 
     val compileKotlinTaskName: String
 
+    val compileKotlinTask: KotlinCompile<T>
+
+    val kotlinOptions: T
+
+    fun kotlinOptions(configure: T.() -> Unit)
+
     val compileAllTaskName: String
 
     companion object {
@@ -51,7 +60,7 @@ interface KotlinCompilation: Named, HasAttributes, HasKotlinDependencies {
         get() = super.relatedConfigurationNames + compileDependencyConfigurationName
 }
 
-interface KotlinCompilationToRunnableFiles : KotlinCompilation {
+interface KotlinCompilationToRunnableFiles<T : KotlinCommonOptions> : KotlinCompilation<T> {
     val runtimeDependencyConfigurationName: String
 
     var runtimeDependencyFiles: FileCollection
@@ -60,6 +69,6 @@ interface KotlinCompilationToRunnableFiles : KotlinCompilation {
         get() = super.relatedConfigurationNames + runtimeDependencyConfigurationName
 }
 
-interface KotlinCompilationWithResources : KotlinCompilation {
+interface KotlinCompilationWithResources<T : KotlinCommonOptions> : KotlinCompilation<T> {
     val processResourcesTaskName: String
 }

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinGradleSubplugin.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.Project
 import org.gradle.api.tasks.compile.AbstractCompile
+import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 import java.io.File
 
 open class SubpluginOption(val key: String, val value: String)
@@ -56,7 +57,7 @@ interface KotlinGradleSubplugin<in KotlinCompile : AbstractCompile> {
         javaCompile: AbstractCompile?,
         variantData: Any?,
         androidProjectHandler: Any?,
-        kotlinCompilation: KotlinCompilation?
+        kotlinCompilation: KotlinCompilation<KotlinCommonOptions>?
     ): List<SubpluginOption>
 
     fun getSubpluginKotlinTasks(

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinTarget.kt

@@ -14,19 +14,21 @@ import org.gradle.api.attributes.HasAttributes
 import org.gradle.api.component.SoftwareComponent
 import org.gradle.api.internal.component.UsageContext
 import org.gradle.api.publish.maven.MavenPublication
+import org.gradle.util.ConfigureUtil
+import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 
 interface KotlinTargetComponent : SoftwareComponent {
     val target: KotlinTarget
     val publishable: Boolean
 }
 
-interface KotlinTarget: Named, HasAttributes {
+interface KotlinTarget : Named, HasAttributes {
     val targetName: String
     val disambiguationClassifier: String? get() = targetName
 
     val platformType: KotlinPlatformType
 
-    val compilations: NamedDomainObjectContainer<out KotlinCompilation>
+    val compilations: NamedDomainObjectContainer<out KotlinCompilation<KotlinCommonOptions>>
 
     val project: Project