Gradle: do not set fragments/fragmentRefines for non-MPP

Otherwise kapt-generated Kotlin sources do not end up in any module,
which causes an error in KT-58301. The error is only happening with K2
because fragments/fragmentRefines arguments are checked more strictly
than commonSources used in K1.

 #KT-58301 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kapt3IT.kt

@@ -1180,4 +1180,44 @@ open class Kapt3IT : Kapt3BaseIT() {
             }
         }
     }
+
+    @DisplayName("Kapt-generated Kotlin sources can be used in Kotlin")
+    @GradleTest
+    internal fun useGeneratedKotlinSource(gradleVersion: GradleVersion) {
+        project("useGeneratedKotlinSource".withPrefix, gradleVersion) {
+            build("build") {
+                assertKaptSuccessful()
+                assertTasksExecuted(":kaptGenerateStubsKotlin", ":kaptKotlin", ":compileKotlin")
+            }
+        }
+    }
+
+    @DisplayName("Kapt-generated Kotlin sources can be used in Kotlin with languageVersion = 2.0")
+    @GradleTest
+    internal fun useGeneratedKotlinSourceK2(gradleVersion: GradleVersion) {
+        project("useGeneratedKotlinSource".withPrefix, gradleVersion) {
+            buildGradle.appendText(
+                """
+                |tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).configureEach {
+                |    compilerOptions {
+                |        freeCompilerArgs.addAll([
+                |            "-Xuse-fir-ic",
+                |            "-Xuse-fir-lt"
+                |        ])
+                |    }
+                |    kotlinOptions {
+                |      languageVersion = "2.0"
+                |    }
+                |}
+                |
+                |compileKotlin.kotlinOptions.allWarningsAsErrors = false
+                """.trimMargin()
+            )
+            build("build") {
+                assertKaptSuccessful()
+                assertTasksExecuted(":kaptGenerateStubsKotlin", ":kaptKotlin", ":compileKotlin")
+                assertOutputContains("Falling back to 1.9.")
+            }
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/build.gradle

@@ -0,0 +1,17 @@
+plugins {
+    id "java"
+    id "org.jetbrains.kotlin.jvm"
+    id "org.jetbrains.kotlin.kapt"
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+dependencies {
+    implementation(project(":processor"))
+    kapt(project(":processor"))
+}
+
+compileKotlin.kotlinOptions.allWarningsAsErrors = true

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/processor/build.gradle

@@ -0,0 +1,11 @@
+plugins {
+    id "java"
+    id "org.jetbrains.kotlin.jvm"
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+compileKotlin.kotlinOptions.allWarningsAsErrors = true

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/processor/src/main/java/GenerateKotlinSourceFile.kt

@@ -0,0 +1,30 @@
+package processor
+
+import javax.annotation.processing.AbstractProcessor
+import javax.annotation.processing.RoundEnvironment
+import javax.lang.model.SourceVersion
+import javax.lang.model.element.TypeElement
+import javax.tools.StandardLocation
+
+class GenerateKotlinSourceFile : AbstractProcessor() {
+    override fun process(annotations: Set<TypeElement>, roundEnv: RoundEnvironment): Boolean {
+        val annotation = annotations.singleOrNull() ?: return true
+        for (type in roundEnv.getElementsAnnotatedWith(annotation)) {
+            if (type !is TypeElement) continue
+            val packageName = processingEnv.elementUtils.getPackageOf(type).qualifiedName.toString()
+            val simpleName = type.simpleName.toString() + "Generated"
+            val file = processingEnv.filer.createResource(StandardLocation.SOURCE_OUTPUT, "example", "$simpleName.kt", type)
+            file.openWriter().use { writer ->
+                writer.write("package $packageName\n\nclass $simpleName")
+            }
+        }
+
+        return true
+    }
+
+    override fun getSupportedSourceVersion(): SourceVersion =
+        SourceVersion.RELEASE_6
+
+    override fun getSupportedAnnotationTypes(): Set<String> =
+        setOf("example.Generate")
+}

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/processor/src/main/resources/META-INF/services/javax.annotation.processing.Processor

@@ -0,0 +1 @@
+processor.GenerateKotlinSourceFile

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/settings.gradle

@@ -0,0 +1 @@
+include "processor"

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/kapt2/useGeneratedKotlinSource/src/main/java/test.kt

@@ -0,0 +1,8 @@
+package example
+
+annotation class Generate
+
+@Generate
+class TestClass
+
+fun testClass(): TestClassGenerated = TestClassGenerated()

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/tasks/KotlinCompile.kt

@@ -230,7 +230,7 @@ abstract class KotlinCompile @Inject constructor(
 
             args.javaPackagePrefix = javaPackagePrefix
 
-            if (compilerOptions.usesK2.get()) {
+            if (compilerOptions.usesK2.get() && multiPlatformEnabled.get()) {
                 args.fragments = multiplatformStructure.fragmentsCompilerArgs
                 args.fragmentRefines = multiplatformStructure.fragmentRefinesCompilerArgs
             }