[Gradle] Project.getCommonizerTarget(sourceSet: KotlinSourceSet): Ignore orphan source sets

Orphan source set's (source sets without compilation) can't break any
compilation. The decision to ignore those source sets for determining
the platform was already done for the IDE import.
In order to stay consistent, this function also ignores orphans.

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

@@ -177,4 +177,32 @@ class SourceSetCommonizerTargetTest {
 
         assertNull(project.getCommonizerTarget(nativeMain), "Expected no commonizer target, since no real source set hierarchy is given")
     }
+
+    @Test
+    fun `orphan source sets are ignored`() {
+        val linux1 = kotlin.linuxX64("linux1")
+        val linux2 = kotlin.linuxArm64("linux2")
+        val nativeMain = kotlin.sourceSets.create("nativeMain")
+        val linux1Main = kotlin.sourceSets.getByName("linux1Main")
+        val linux2Main = kotlin.sourceSets.getByName("linux2Main")
+        val orphan = kotlin.sourceSets.create("orphan")
+
+        linux1Main.dependsOn(nativeMain)
+        linux2Main.dependsOn(nativeMain)
+        orphan.dependsOn(nativeMain)
+
+        assertEquals(CommonizerTarget(linux1.konanTarget, linux2.konanTarget), project.getCommonizerTarget(nativeMain))
+    }
+
+    @Test
+    fun `orphan source sets only`() {
+        val nativeMain = kotlin.sourceSets.create("nativeMain")
+        val orphan1 = kotlin.sourceSets.create("orphan1")
+        val orphan2 = kotlin.sourceSets.create("orphan2")
+
+        orphan1.dependsOn(nativeMain)
+        orphan2.dependsOn(nativeMain)
+
+        assertEquals(null, project.getCommonizerTarget(nativeMain))
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/native/internal/GetCommonizerTargetOfSourceSet.kt

@@ -13,15 +13,17 @@ import org.jetbrains.kotlin.commonizer.allLeaves
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtensionOrNull
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
-import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSetContainer
 import org.jetbrains.kotlin.gradle.plugin.mpp.CompilationSourceSetUtil.compilationsBySourceSets
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinNativeCompilation
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinSharedNativeCompilation
+import org.jetbrains.kotlin.gradle.plugin.sources.resolveAllSourceSetsDependingOn
 import org.jetbrains.kotlin.konan.target.KonanTarget
 
 internal fun Project.getCommonizerTarget(sourceSet: KotlinSourceSet): CommonizerTarget? {
     val kotlin = multiplatformExtensionOrNull ?: return null
-    val sourceSetsDependingOnThisSourceSet = kotlin.resolveSourceSetsDirectlyDependingOn(sourceSet)
+    val sourceSetsDependingOnThisSourceSet = kotlin.resolveAllSourceSetsDependingOn(sourceSet)
+        .filterNot(::isOrphanSourceSet)
+
     if (sourceSetsDependingOnThisSourceSet.isEmpty()) {
         return getLeafCommonizerTarget(sourceSet)
     }
@@ -50,16 +52,8 @@ private fun Project.getLeafCommonizerTarget(sourceSet: KotlinSourceSet): LeafCom
     else null
 }
 
-private fun KotlinSourceSetContainer.resolveSourceSetsDirectlyDependingOn(sourceSet: KotlinSourceSet): Set<KotlinSourceSet> {
-    val dependeeSourceSets = sourceSets
-        .filter { candidateSourceSet -> candidateSourceSet != sourceSet }
-        .filter { candidateSourceSet -> sourceSet in candidateSourceSet.dependsOn }
-
-    fun isTransitiveDependee(sourceSet: KotlinSourceSet): Boolean {
-        return sourceSet.dependsOn.any { it in dependeeSourceSets || isTransitiveDependee(it) }
-    }
-
-    return dependeeSourceSets.filterNot(::isTransitiveDependee).toSet()
+private fun Project.isOrphanSourceSet(sourceSet: KotlinSourceSet): Boolean {
+    return compilationsBySourceSets(this)[sourceSet].orEmpty().isEmpty()
 }
 
 private val KotlinCompilation<*>.konanTargets: Set<KonanTarget>
@@ -70,3 +64,4 @@ private val KotlinCompilation<*>.konanTargets: Set<KonanTarget>
             else -> emptySet()
         }
     }
+