[FIR] Handle expect declarations in JVM backend

1. Do not generate bytecode for expect declarations

2. Serialize @OptionalExpectation annotations into .kotlin_module file

^KT-62931: Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/ClassFileFactory.java

@@ -116,7 +116,6 @@ public class ClassFileFactory implements OutputFileCollection {
     public void done() {
         if (!isDone) {
             isDone = true;
-            writeModuleMappings();
             for (ClassFileFactoryFinalizerExtension extension : finalizers) {
                 extension.finalizeClassFactory(this);
             }
@@ -127,20 +126,8 @@ public class ClassFileFactory implements OutputFileCollection {
         generators.clear();
     }
 
-    private void writeModuleMappings() {
-        JvmModuleProtoBuf.Module.Builder builder = JvmModuleProtoBuf.Module.newBuilder();
-        String outputFilePath = getMappingFileName(state.getModuleName());
-
-        StringTableImpl stringTable = new StringTableImpl();
-        ClassFileUtilsKt.addDataFromCompiledModule(builder, packagePartRegistry, stringTable, state);
-
-        Pair<ProtoBuf.StringTable, ProtoBuf.QualifiedNameTable> tables = stringTable.buildProto();
-        builder.setStringTable(tables.getFirst());
-        builder.setQualifiedNameTable(tables.getSecond());
-
-        JvmModuleProtoBuf.Module moduleProto = builder.build();
-
-        generators.put(outputFilePath, new OutAndSourceFileList(CollectionsKt.toList(sourceFiles)) {
+    public void setModuleMapping(JvmModuleProtoBuf.Module moduleProto) {
+        generators.put(getMappingFileName(state.getModuleName()), new OutAndSourceFileList(CollectionsKt.toList(sourceFiles)) {
             @Override
             public byte[] asBytes(ClassBuilderFactory factory) {
                 int flags = 0;

compiler/backend/src/org/jetbrains/kotlin/codegen/CodegenFactory.kt

@@ -23,10 +23,12 @@ import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil
+import org.jetbrains.kotlin.metadata.jvm.JvmModuleProtoBuf
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStatus
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.serialization.StringTableImpl
 
 interface CodegenFactory {
     fun convertToIr(input: IrConversionInput): BackendInput
@@ -126,7 +128,20 @@ object DefaultCodegenFactory : CodegenFactory {
     }
 
     override fun invokeCodegen(input: CodegenFactory.CodegenInput) {
-        // Do nothing
+        generateModuleMetadata(input)
+    }
+
+    private fun generateModuleMetadata(result: CodegenFactory.CodegenInput) {
+        val builder = JvmModuleProtoBuf.Module.newBuilder()
+
+        val stringTable = StringTableImpl()
+        builder.addDataFromCompiledModule(stringTable, result.state)
+
+        val (stringTableProto, qualifiedNameTableProto) = stringTable.buildProto()
+        builder.setStringTable(stringTableProto)
+        builder.setQualifiedNameTable(qualifiedNameTableProto)
+
+        result.state.factory.setModuleMapping(builder.build())
     }
 
     private fun generateMultifileClass(state: GenerationState, multifileClassFqName: FqName, files: Collection<KtFile>) {

compiler/backend/src/org/jetbrains/kotlin/codegen/PackagePartRegistry.kt

@@ -22,6 +22,8 @@ import org.jetbrains.kotlin.name.FqName
 
 class PackagePartRegistry {
     val parts = mutableMapOf<FqName, PackageParts>()
+
+    // Drop after old BE removal
     val optionalAnnotations = mutableListOf<ClassDescriptor>()
 
     fun addPart(packageFqName: FqName, partInternalName: String, facadeInternalName: String?) {

compiler/backend/src/org/jetbrains/kotlin/codegen/classFileUtils.kt

@@ -37,9 +37,8 @@ fun List<OutputFile>.filterClassFiles(): List<OutputFile> {
     return filter { it.relativePath.endsWith(".class") }
 }
 
-fun JvmModuleProtoBuf.Module.Builder.addDataFromCompiledModule(
-    registry: PackagePartRegistry, stringTable: StringTableImpl, state: GenerationState
-) {
+fun JvmModuleProtoBuf.Module.Builder.addDataFromCompiledModule(stringTable: StringTableImpl, state: GenerationState) {
+    val registry = state.factory.packagePartRegistry
     for (part in registry.parts.values.addCompiledPartsAndSort(state)) {
         part.addTo(this)
     }
@@ -74,7 +73,7 @@ class JvmOptionalAnnotationSerializerExtension(
     override fun shouldUseTypeTable(): Boolean = true
 }
 
-private fun Iterable<PackageParts>.addCompiledPartsAndSort(state: GenerationState): List<PackageParts> =
+fun Iterable<PackageParts>.addCompiledPartsAndSort(state: GenerationState): List<PackageParts> =
     addCompiledParts(state).sortedBy { it.packageFqName }
 
 private fun Iterable<PackageParts>.addCompiledParts(state: GenerationState): List<PackageParts> {
@@ -94,7 +93,7 @@ private fun Iterable<PackageParts>.addCompiledParts(state: GenerationState): Lis
         }
 }
 
-private fun GenerationState.loadCompiledModule(): ModuleMapping? {
+fun GenerationState.loadCompiledModule(): ModuleMapping? {
     val moduleMappingData = incrementalCacheForThisTarget?.getModuleMappingData() ?: return null
     return ModuleMapping.loadModuleMapping(moduleMappingData, "<incremental>", deserializationConfiguration) { version ->
         throw IllegalStateException("Version of the generated module cannot be incompatible: $version")