[Gradle][MPP] Replace InternalKotlinSourceSet.addCompilation by exposing mutable .compilations

This requires to make MutableObservableSet public as well, since
public implementations will inherit. The MutableObservableSet
therefore move its implementation to an internal
MutableObservableSetImpl

^KT-52726 Verification Pending

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/AbstractCompilationDetails.kt

@@ -8,19 +8,19 @@ package org.jetbrains.kotlin.gradle.plugin.mpp
 import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.sources.internal
-import org.jetbrains.kotlin.gradle.utils.MutableObservableSet
+import org.jetbrains.kotlin.gradle.utils.MutableObservableSetImpl
 import org.jetbrains.kotlin.gradle.utils.ObservableSet
 
 abstract class AbstractCompilationDetails<T : KotlinCommonOptions> : CompilationDetails<T> {
-    private val directlyIncludedKotlinSourceSetsImpl: MutableObservableSet<KotlinSourceSet> by lazy {
+    private val directlyIncludedKotlinSourceSetsImpl: MutableObservableSetImpl<KotlinSourceSet> by lazy {
-        MutableObservableSet(defaultSourceSet)
+        MutableObservableSetImpl(defaultSourceSet)
     }
 
     final override val directlyIncludedKotlinSourceSets: ObservableSet<KotlinSourceSet>
         get() = directlyIncludedKotlinSourceSetsImpl
 
-    private val allKotlinSourceSetsImpl: MutableObservableSet<KotlinSourceSet> by lazy {
+    private val allKotlinSourceSetsImpl: MutableObservableSetImpl<KotlinSourceSet> by lazy {
-        MutableObservableSet<KotlinSourceSet>().also { set ->
+        MutableObservableSetImpl<KotlinSourceSet>().also { set ->
             defaultSourceSet.internal.withDependsOnClosure.forAll(set::add)
         }
     }
@@ -40,7 +40,7 @@ abstract class AbstractCompilationDetails<T : KotlinCommonOptions> : Compilation
         directlyIncludedKotlinSourceSetsImpl.add(sourceSet)
         sourceSet.internal.withDependsOnClosure.forAll { inDependsOnClosure ->
             allKotlinSourceSetsImpl.add(inDependsOnClosure)
-            inDependsOnClosure.internal.addCompilation(compilation)
+            inDependsOnClosure.internal.compilations.add(compilation)
         }
 
         whenSourceSetAdded(sourceSet)

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/AbstractKotlinSourceSet.kt

@@ -10,13 +10,13 @@ package org.jetbrains.kotlin.gradle.plugin.sources
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.utils.MutableObservableSet
+import org.jetbrains.kotlin.gradle.utils.MutableObservableSetImpl
 import org.jetbrains.kotlin.gradle.utils.ObservableSet
 
 abstract class AbstractKotlinSourceSet : InternalKotlinSourceSet {
-    private val dependsOnImpl = MutableObservableSet<KotlinSourceSet>()
+    private val dependsOnImpl = MutableObservableSetImpl<KotlinSourceSet>()
-    private val dependsOnClosureImpl = MutableObservableSet<KotlinSourceSet>()
+    private val dependsOnClosureImpl = MutableObservableSetImpl<KotlinSourceSet>()
-    private val withDependsOnClosureImpl = MutableObservableSet<KotlinSourceSet>(this)
+    private val withDependsOnClosureImpl = MutableObservableSetImpl<KotlinSourceSet>(this)
-    private val compilationsImpl = MutableObservableSet<KotlinCompilation<*>>()
 
     final override val dependsOn: ObservableSet<KotlinSourceSet>
         get() = dependsOnImpl
@@ -27,8 +27,7 @@ abstract class AbstractKotlinSourceSet : InternalKotlinSourceSet {
     final override val withDependsOnClosure: ObservableSet<KotlinSourceSet>
         get() = withDependsOnClosureImpl
 
-    override val compilations: ObservableSet<KotlinCompilation<*>>
+    override val compilations: MutableObservableSet<KotlinCompilation<*>> = MutableObservableSetImpl()
-        get() = compilationsImpl
 
     final override fun dependsOn(other: KotlinSourceSet) {
         if (other == this) return
@@ -51,9 +50,5 @@ abstract class AbstractKotlinSourceSet : InternalKotlinSourceSet {
     }
 
     protected open fun afterDependsOnAdded(other: KotlinSourceSet) = Unit
-
-    final override fun addCompilation(compilation: KotlinCompilation<*>) {
-        compilationsImpl.add(compilation)
-    }
 }
 

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/InternalKotlinSourceSet.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.gradle.plugin.sources
 
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
+import org.jetbrains.kotlin.gradle.utils.MutableObservableSet
 import org.jetbrains.kotlin.gradle.utils.ObservableSet
 
 internal val KotlinSourceSet.internal: InternalKotlinSourceSet
@@ -18,6 +19,5 @@ internal interface InternalKotlinSourceSet : KotlinSourceSet {
     override val dependsOn: ObservableSet<KotlinSourceSet>
     val dependsOnClosure: ObservableSet<KotlinSourceSet>
     val withDependsOnClosure: ObservableSet<KotlinSourceSet>
-    val compilations: ObservableSet<KotlinCompilation<*>>
+    val compilations: MutableObservableSet<KotlinCompilation<*>>
-    fun addCompilation(compilation: KotlinCompilation<*>)
 }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/utils/ObservableSet.kt

@@ -10,7 +10,9 @@ interface ObservableSet<T> : Set<T> {
     fun forAll(action: (T) -> Unit)
 }
 
-internal class MutableObservableSet<T>(vararg elements: T) : ObservableSet<T>, MutableSet<T> {
+interface MutableObservableSet<T> : ObservableSet<T>, MutableSet<T>
+
+internal class MutableObservableSetImpl<T>(vararg elements: T) : MutableObservableSet<T> {
     private val underlying = mutableSetOf(*elements)
     private val whenObjectAddedActions = mutableListOf<(T) -> Unit>()
     private val forAllActions = mutableListOf<(T) -> Unit>()

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/ObservableSetTest.kt

@@ -7,7 +7,7 @@
 
 package org.jetbrains.kotlin.gradle
 
-import org.jetbrains.kotlin.gradle.utils.MutableObservableSet
+import org.jetbrains.kotlin.gradle.utils.MutableObservableSetImpl
 import org.junit.Test
 import kotlin.test.assertEquals
 
@@ -22,7 +22,7 @@ class ObservableSetTest {
 
     @Test
     fun `test - forAll`() {
-        val set = MutableObservableSet(1)
+        val set = MutableObservableSetImpl(1)
         val testListener1 = TestListener()
         val testListener2 = TestListener()
 
@@ -41,7 +41,7 @@ class ObservableSetTest {
 
     @Test
     fun `test - whenObjectAdded`() {
-        val set = MutableObservableSet(1)
+        val set = MutableObservableSetImpl(1)
         val testListener1 = TestListener()
         val testListener2 = TestListener()