MPP: Force COMMON platform for commonMain/commonTest source sets

Also set isTestModule flag for them according to source set name alone

 #KT-26356 Fixed

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModel.kt

@@ -23,6 +23,11 @@ interface KotlinSourceSet : KotlinModule {
     val sourceDirs: Set<File>
     val resourceDirs: Set<File>
     val dependsOnSourceSets: Set<String>
+
+    companion object {
+        const val COMMON_MAIN_SOURCE_SET_NAME = "commonMain"
+        const val COMMON_TEST_SOURCE_SET_NAME = "commonTest"
+    }
 }
 
 interface KotlinLanguageSettings : Serializable {

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelBuilder.kt

@@ -308,6 +308,18 @@ class KotlinMPPGradleModelBuilder : ModelBuilderService {
             }
         }
         for (sourceSet in sourceSets) {
+            val name = sourceSet.name
+            if (name == KotlinSourceSet.COMMON_MAIN_SOURCE_SET_NAME) {
+                sourceSet.platform = KotlinPlatform.COMMON
+                sourceSet.isTestModule = false
+                continue
+            }
+            if (name == KotlinSourceSet.COMMON_TEST_SOURCE_SET_NAME) {
+                sourceSet.platform = KotlinPlatform.COMMON
+                sourceSet.isTestModule = true
+                continue
+            }
+
             val compilations = sourceSetToCompilations[sourceSet]
             if (compilations != null) {
                 sourceSet.platform = compilations.map { it.platform }.distinct().singleOrNull() ?: KotlinPlatform.COMMON

idea/kotlin-gradle-tooling/src/KotlinMPPGradleModelBuilder.kt.181

@@ -308,6 +308,18 @@ class KotlinMPPGradleModelBuilder : ModelBuilderService {
             }
         }
         for (sourceSet in sourceSets) {
+            val name = sourceSet.name
+            if (name == KotlinSourceSet.COMMON_MAIN_SOURCE_SET_NAME) {
+                sourceSet.platform = KotlinPlatform.COMMON
+                sourceSet.isTestModule = false
+                continue
+            }
+            if (name == KotlinSourceSet.COMMON_TEST_SOURCE_SET_NAME) {
+                sourceSet.platform = KotlinPlatform.COMMON
+                sourceSet.isTestModule = true
+                continue
+            }
+
             val compilations = sourceSetToCompilations[sourceSet]
             if (compilations != null) {
                 sourceSet.platform = compilations.map { it.platform }.distinct().singleOrNull() ?: KotlinPlatform.COMMON