Reimplement friend task/friend paths using associated compilations

Replace the old ad-hoc task matching mechanism used for connecting the
compilation tasks that need to share internal visibility with an
implementation based on the associate compilations and compilation
outputs rather than `destinationDir`s of the tasks.

The only place that still requires ad-hoc friend paths is the Android
instrumented tests compiling against the JAR of the main variant, not
its classes dirs. Support that with `friendArtifacts`.

Issue #KT-17630 Fixed
Issue #KT-20760 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/NewMultiplatformIT.kt

@@ -2041,4 +2041,31 @@ class NewMultiplatformIT : BaseGradleIT() {
             assertNotContains(DISABLED_NATIVE_TARGETS_REPORTER_WARNING_PREFIX)
         }
     }
+
+    @Test
+    fun testAssociateCompilations() = with(Project("new-mpp-associate-compilations")) {
+        setupWorkingDir()
+        gradleBuildScript().modify(::transformBuildScriptWithPluginsDsl)
+
+        val tasks = listOf("jvm", "js", nativeHostTargetName).map { ":compileIntegrationTestKotlin${it.capitalize()}" }
+
+        build(*tasks.toTypedArray()) {
+            assertSuccessful()
+            assertTasksExecuted(*tasks.toTypedArray())
+
+            // JVM:
+            checkBytecodeContains(
+                projectDir.resolve("build/classes/kotlin/jvm/integrationTest/com/example/HelloIntegrationTest.class"),
+                "Hello.internalFun\$new_mpp_associate_compilations",
+                "HelloTest.internalTestFun\$new_mpp_associate_compilations"
+            )
+            assertFileExists("build/classes/kotlin/jvm/integrationTest/META-INF/new-mpp-associate-compilations.kotlin_module")
+
+            // JS:
+            assertFileExists("build/classes/kotlin/js/integrationTest/new-mpp-associate-compilations_integrationTest.js")
+
+            // Native:
+            assertFileExists("build/classes/kotlin/$nativeHostTargetName/integrationTest/integrationTest.klib")
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/build.gradle.kts

@@ -34,9 +34,7 @@ kotlin.target.compilations {
 
     val benchmark by creating {
         defaultSourceSet.dependencies {
-            implementation(main.compileDependencyFiles + main.output.allOutputs)
-            runtimeOnly(main.runtimeDependencyFiles)
-
+            associateWith(main)
             implementation(kotlin("reflect"))
         }
     }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/src/benchmark/kotlin/ABenchmark.kt

@@ -3,6 +3,7 @@ package com.example
 fun main() {
     val a = A()
     val f = a::f
+    internalFun()
     f()
     println("${a::f.name} ran at the speed of light")
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-model-in-old-plugin/src/main/kotlin/A.kt

@@ -2,4 +2,6 @@ package com.example
 
 class A {
     fun f(): String = "hello".also(::println)
-}
+}
+
+fun internalFun() = 1

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-associate-compilations/build.gradle

@@ -0,0 +1,56 @@
+plugins {
+    id("org.jetbrains.kotlin.multiplatform").version("<pluginMarkerVersion>")
+}
+
+repositories {
+    mavenLocal()
+    jcenter()
+}
+
+kotlin {
+    sourceSets {
+        getByName("commonMain") {
+            dependencies {
+                implementation(kotlin("stdlib-common"))
+            }
+        }
+
+        getByName("commonTest") {
+            dependencies {
+                implementation(kotlin("test-common"))
+                implementation(kotlin("test-annotations-common"))
+            }
+        }
+
+        create("commonIntegrationTest")
+    }
+
+    jvm {
+        compilations["main"].defaultSourceSet.dependencies {
+            implementation(kotlin("stdlib"))
+        }
+        compilations["test"].defaultSourceSet.dependencies {
+            implementation(kotlin("test-junit"))
+        }
+    }
+
+    js {
+        compilations["main"].defaultSourceSet.dependencies {
+            implementation(kotlin("stdlib-js"))
+        }
+        compilations["test"].defaultSourceSet.dependencies {
+            implementation(kotlin("test-js"))
+        }
+    }
+
+    mingwX64("mingw64") {}
+    linuxX64("linux64") {}
+    macosX64("macos64") {}
+
+    targets.matching { it.name != "metadata" }.all {
+        compilations.create("integrationTest") {
+            associateWith(compilations["test"])
+            defaultSourceSet.dependsOn(sourceSets["commonIntegrationTest"])
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-associate-compilations/settings.gradle.kts

@@ -0,0 +1,8 @@
+pluginManagement {
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+    }
+}
+
+rootProject.name = "new-mpp-associate-compilations"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-associate-compilations/src/commonIntegrationTest/kotlin/HelloIntegrationTest.kt

@@ -0,0 +1,24 @@
+package com.example
+
+import kotlin.test.Test
+
+class HelloIntegrationTest {
+    @Test
+    fun test(): Unit = Hello().run {
+        hello()
+        internalFun()
+
+        HelloTest().run {
+            test()
+            internalTestFun()
+        }
+    }
+
+    @Test
+    fun secondTest() = Unit
+
+    @Test
+    fun thirdTest() = Unit
+}
+
+fun topLevelMemberToMakeTheCompilerGenerateTheModuleFile() = 1

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-associate-compilations/src/commonMain/kotlin/Hello.kt

@@ -0,0 +1,6 @@
+package com.example
+
+class Hello {
+    fun hello() = 0
+    internal fun internalFun() = 1
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-associate-compilations/src/commonTest/kotlin/HelloTest.kt

@@ -0,0 +1,19 @@
+package com.example
+
+import kotlin.test.Test
+
+class HelloTest {
+    @Test
+    fun test(): Unit = Hello().run {
+        hello()
+        internalFun()
+    }
+
+    @Test
+    fun secondTest() = Unit
+
+    @Test
+    fun thirdTest() = Unit
+
+    internal fun internalTestFun() = 1
+}