[Gradle] Introduce getHostSpecificMainSharedSourceSets

^KT-48839

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/native/KotlinNativeTarget.kt

@@ -186,6 +186,27 @@ internal fun getHostSpecificSourceSets(project: Project): Set<KotlinSourceSet> {
     )
 }
 
+/**
+ * Returns all host-specific source sets that will be compiled to two or more targets
+ */
+internal fun getHostSpecificMainSharedSourceSets(project: Project): Set<KotlinSourceSet> {
+    fun KotlinSourceSet.testOnly(): Boolean = internal.compilations.all { it.isTest() }
+
+    fun KotlinSourceSet.isCompiledToSingleTarget(): Boolean {
+        return internal
+            .compilations
+            // if for some reason [it.target] is not a [KotlinNativeTarget] then assume that it is not a host-specific source set
+            .distinctBy { (it.target as? KotlinNativeTarget)?.konanTarget ?: return false }
+            .size == 1
+    }
+
+    return getHostSpecificSourceSets(project)
+        .filterNot { it.testOnly() }
+        .filterNot { it.isCompiledToSingleTarget() }
+        .toSet()
+}
+
+
 abstract class KotlinNativeTargetWithTests<T : KotlinNativeBinaryTestRun>(
     project: Project,
     konanTarget: KonanTarget

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

@@ -10,10 +10,12 @@ package org.jetbrains.kotlin.gradle.sources
 import org.jetbrains.kotlin.gradle.assertAllImplementationsAlsoImplement
 import org.jetbrains.kotlin.gradle.buildProjectWithMPP
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
+import org.jetbrains.kotlin.gradle.kotlin
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
 import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.sources.InternalKotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.sources.internal
+import org.jetbrains.kotlin.gradle.plugin.mpp.getHostSpecificMainSharedSourceSets
 import org.jetbrains.kotlin.gradle.reflections
 import org.junit.jupiter.api.assertAll
 import kotlin.reflect.full.isSubclassOf
@@ -106,4 +108,64 @@ class InternalKotlinSourceSetTest {
             linuxX64Main.internal.withDependsOnClosure
         )
     }
+
+    @Test
+    fun `test getHostSpecificMainSharedSourceSets`() {
+        val project = buildProjectWithMPP {
+            kotlin {
+                jvm()
+                linuxX64()
+                linuxArm64()
+                ios() // host specific from preset
+            }
+        }
+
+        val kotlin = project.multiplatformExtension
+        
+        with(kotlin.sourceSets) {
+            val commonMain = getByName("commonMain")
+            val commonTest = getByName("commonTest")
+            val iosMain = getByName("iosMain")
+            val iosTest = getByName("iosTest")
+
+            val iosX64Main = getByName("iosX64Main")
+            val iosArm64Main = getByName("iosArm64Main")
+            val iosX64Test = getByName("iosX64Test")
+            val iosArm64Test = getByName("iosArm64Test")
+
+            val linuxX64Main = getByName("linuxX64Main")
+            val linuxArm64Main = getByName("linuxArm64Main")
+            val linuxX64Test = getByName("linuxX64Test")
+            val linuxArm64Test = getByName("linuxArm64Test")
+
+            // common -> ios2 -> ios
+            create("ios2Main") { it.dependsOn(commonMain); iosMain.dependsOn(it) }
+            create("ios2Test") { it.dependsOn(commonTest); iosTest.dependsOn(it) }
+
+            // ... -> ios -> ios2{X64,Arm64} -> ios{X64,Arm64}
+            create("ios2X64Main") { it.dependsOn(iosMain); iosX64Main.dependsOn(it) }
+            create("ios2X64Test") { it.dependsOn(iosTest); iosX64Test.dependsOn(it) }
+            create("ios2Arm64Main") { it.dependsOn(iosMain); iosArm64Main.dependsOn(it) }
+            create("ios2Arm64Test") { it.dependsOn(iosTest); iosArm64Test.dependsOn(it) }
+
+            // common -> linux
+            create("linuxMain") {
+                it.dependsOn(commonMain)
+                linuxX64Main.dependsOn(it)
+                linuxArm64Main.dependsOn(it)
+            }
+            create("linuxTest") {
+                it.dependsOn(commonTest)
+                linuxX64Test.dependsOn(it)
+                linuxArm64Test.dependsOn(it)
+            }
+        }
+
+        project.evaluate()
+
+        val expected = listOf("iosMain", "ios2Main").sorted()
+        val actual = getHostSpecificMainSharedSourceSets(project).map { it.name }.sorted()
+
+        assertEquals(expected, actual)
+    }
 }