Implement associate compilations, KT-34009

Partial implementation of the associate compilations proposal. A
compilation can now contain links to other compilation that it compiles
against. This links will replace ad-hoc inter-compilation dependencies.

Issue #KT-34009 Fixed

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

@@ -67,6 +67,10 @@ interface KotlinCompilation<out T : KotlinCommonOptions> : Named, HasAttributes,
 
     fun source(sourceSet: KotlinSourceSet)
 
+    fun associateWith(other: KotlinCompilation<*>)
+
+    val associateWith: Set<KotlinCompilation<*>>
+
     override fun getName(): String = compilationName
 
     override val relatedConfigurationNames: List<String>

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

@@ -476,6 +476,10 @@ internal abstract class AbstractKotlinPlugin(
                 kotlinCompilation.source(kotlinSourceSet)
             }
 
+            kotlinTarget.compilations.run {
+                getByName(KotlinCompilation.TEST_COMPILATION_NAME).associateWith(getByName(KotlinCompilation.MAIN_COMPILATION_NAME))
+            }
+
             // Since the 'java' plugin (as opposed to 'java-library') doesn't known anything about the 'api' configurations,
             // add the API dependencies of the main compilation directly to the 'apiElements' configuration, so that the 'api' dependencies
             // are properly published with the 'compile' scope (KT-28355):
@@ -939,6 +943,12 @@ abstract class AbstractAndroidProjectHandler(private val kotlinConfigurationTool
     ) {
         val javaTask = getJavaTask(variantData) ?: return
 
+        getTestedVariantData(variantData)?.let { testedVariant ->
+            val testedVariantName = getVariantName(testedVariant)
+            val testedCompilation = compilation.target.compilations.getByName(testedVariantName)
+            compilation.associateWith(testedCompilation)
+        }
+
         val kotlinTask = compilation.compileKotlinTask
         configureSources(kotlinTask, variantData, compilation)
         wireKotlinTasks(project, compilation, androidPlugin, androidExt, variantData, javaTask, kotlinTask)

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

@@ -81,10 +81,11 @@ abstract class AbstractKotlinTargetConfigurator<KotlinTargetType : KotlinTarget>
 
         if (createTestCompilation) {
             target.compilations.create(KotlinCompilation.TEST_COMPILATION_NAME).apply {
-                compileDependencyFiles += main.output.allOutputs
+                associateWith(main)
 
                 if (this is KotlinCompilationToRunnableFiles) {
-                    runtimeDependencyFiles += project.files(output.allOutputs, main.output.allOutputs)
+                    // TODO: fix inconsistency? KT-27272
+                    runtimeDependencyFiles += project.files(output.allOutputs)
                 }
             }
         }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/kotlinCompilations.kt

@@ -199,8 +199,50 @@ abstract class AbstractKotlinCompilation<T : KotlinCommonOptions>(
             val suffix = if (compilationName == KotlinCompilation.MAIN_COMPILATION_NAME) "" else "_$compilationName"
             return filterModuleName("$baseName$suffix")
         }
+
+    override fun associateWith(other: KotlinCompilation<*>) {
+        require(other.target == target) { "Only associations between compilations of a single target are supported" }
+        other as AbstractKotlinCompilation<*>
+
+        _associateWith += other
+
+        addAssociateCompilationDependencies(other)
+    }
+
+    protected open fun addAssociateCompilationDependencies(other: KotlinCompilation<*>) {
+        target.project.dependencies.run {
+            val project = target.project
+
+            add(
+                compileDependencyConfigurationName,
+                project.files(Callable { other.output.classesDirs }, Callable { other.compileDependencyFiles })
+            )
+
+            if (this@AbstractKotlinCompilation is KotlinCompilationToRunnableFiles<*>) {
+                add(runtimeDependencyConfigurationName, project.files(Callable { other.output.allOutputs }))
+                if (other is KotlinCompilationToRunnableFiles<*>) {
+                    add(runtimeDependencyConfigurationName, project.files(Callable { other.runtimeDependencyFiles }))
+                }
+            }
+        }
+    }
+
+    private val _associateWith: MutableSet<AbstractKotlinCompilation<*>> = mutableSetOf()
+
+    override val associateWith: Set<KotlinCompilation<*>>
+        get() = Collections.unmodifiableSet(_associateWith)
 }
 
+ internal val KotlinCompilation<*>.associateWithTransitiveClosure: Iterable<KotlinCompilation<*>>
+     get() = mutableSetOf<KotlinCompilation<*>>().apply {
+         fun visit(other: KotlinCompilation<*>) {
+             if (add(other)) {
+                 other.associateWith.forEach(::visit)
+             }
+         }
+         associateWith.forEach(::visit)
+     }
+
 abstract class AbstractKotlinCompilationToRunnableFiles<T : KotlinCommonOptions>(
     target: KotlinTarget,
     name: String

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/jvm/KotlinWithJavaCompilation.kt

@@ -9,6 +9,7 @@ package org.jetbrains.kotlin.gradle.plugin.mpp
 import org.gradle.api.file.FileCollection
 import org.gradle.api.tasks.SourceSet
 import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
+import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilationOutput
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilationWithResources
 import org.jetbrains.kotlin.gradle.tasks.AbstractKotlinCompile
@@ -57,6 +58,12 @@ import org.jetbrains.kotlin.gradle.tasks.AbstractKotlinCompile
             javaSourceSet.compileClasspath = value
         }
 
+     override fun addAssociateCompilationDependencies(other: KotlinCompilation<*>) {
+         if (name != SourceSet.TEST_SOURCE_SET_NAME || other.name != SourceSet.MAIN_SOURCE_SET_NAME) {
+             super.addAssociateCompilationDependencies(other)
+         } // otherwise, do nothing: the Java Gradle plugin adds these dependencies for us, we don't need to add them to the classpath
+     }
+
     fun source(javaSourceSet: SourceSet) {
         with(target.project) {
             afterEvaluate {