Introduce GeneratedSerializer and childSerializers

Descriptors passing on JVM

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/common/SerializerCodegen.kt

@@ -42,6 +42,7 @@ abstract class SerializerCodegen(
         val prop = generateSerializableClassPropertyIfNeeded()
         val save = generateSaveIfNeeded()
         val load = generateLoadIfNeeded()
+        generateDescriptorGetterIfNeeded()
 //        if (save || load || prop)
 //            generateSerialDesc()
         if (serializableDescriptor.declaredTypeParameters.isNotEmpty() && typedSerializerConstructorNotDeclared()) {
@@ -49,6 +50,19 @@ abstract class SerializerCodegen(
         }
     }
 
+    private fun generateDescriptorGetterIfNeeded(): Boolean {
+        val function = getMemberToGenerate(
+            serializerDescriptor, SerialEntityNames.GENERATED_DESCRIPTOR_GETTER.identifier,
+            { true }, { true }
+        ) ?: return false
+        generateChildSerializersGetter(function)
+        return true
+    }
+
+    protected open fun generateChildSerializersGetter(function: FunctionDescriptor) {
+        // TODO()
+    }
+
     // checks if user didn't declared constructor (KSerializer<T0>, KSerializer<T1>...) on a KSerializer<T<T0, T1...>>
     private fun typedSerializerConstructorNotDeclared(): Boolean {
         val serializableImplementationTypeArguments = extractKSerializerArgumentFromImplementation(serializerDescriptor)?.arguments

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/JVMCodegenUtil.kt

@@ -55,6 +55,7 @@ import org.jetbrains.org.objectweb.asm.commons.InstructionAdapter
 // todo: extract packages constants too?
 internal val descType = Type.getObjectType("kotlinx/serialization/$SERIAL_DESCRIPTOR_CLASS")
 internal val descImplType = Type.getObjectType("kotlinx/serialization/internal/$SERIAL_DESCRIPTOR_CLASS_IMPL")
+internal val generatedSerializerType = Type.getObjectType("kotlinx/serialization/internal/${SerialEntityNames.GENERATED_SERIALIZER_CLASS}")
 internal val kOutputType = Type.getObjectType("kotlinx/serialization/$STRUCTURE_ENCODER_CLASS")
 internal val encoderType = Type.getObjectType("kotlinx/serialization/$ENCODER_CLASS")
 internal val decoderType = Type.getObjectType("kotlinx/serialization/$DECODER_CLASS")
@@ -168,6 +169,32 @@ internal fun InstructionAdapter.stackValueSerializerInstanceFromClass(
     }
 }
 
+internal fun InstructionAdapter.stackValueSerializerInstanceFromSerializerWithoutSti(
+    codegen: ClassBodyCodegen,
+    property: SerializableProperty,
+    serializerCodegen: AbstractSerialGenerator
+): Boolean {
+    val serializer =
+        property.serializableWith?.toClassDescriptor
+            ?: if (!property.type.isTypeParameter()) serializerCodegen.findTypeSerializerOrContext(
+                property.module,
+                property.type,
+                property.descriptor.annotations,
+                property.descriptor.findPsi()
+            ) else null
+    return serializerCodegen.stackValueSerializerInstance(
+        codegen,
+        property.module,
+        property.type,
+        serializer,
+        this,
+        property.genericIndex
+    ) { idx ->
+        load(0, kSerializerType)
+        getfield(codegen.typeMapper.mapClass(codegen.descriptor).internalName, "$typeArgPrefix$idx", kSerializerType.descriptor)
+    }.also { if (it && property.type.isMarkedNullable) wrapStackValueIntoNullableSerializer() }
+}
+
 internal fun InstructionAdapter.stackValueSerializerInstanceFromSerializer(codegen: ClassBodyCodegen, sti: JVMSerialTypeInfo, serializerCodegen: AbstractSerialGenerator): Boolean {
     return serializerCodegen.stackValueSerializerInstance(
         codegen, sti.property.module, sti.property.type,
@@ -240,13 +267,19 @@ internal fun AbstractSerialGenerator.stackValueSerializerInstance(codegen: Class
         }
         // all serializers get arguments with serializers of their generic types
         argSerializers.forEach { (argType, argSerializer) ->
-            assert(stackValueSerializerInstance(codegen, module, argType, argSerializer, this, argType.genericIndex, genericSerializerFieldGetter))
+            assert(
+                stackValueSerializerInstance(
+                    codegen,
+                    module,
+                    argType,
+                    argSerializer,
+                    this,
+                    argType.genericIndex,
+                    genericSerializerFieldGetter
+                )
+            )
             // wrap into nullable serializer if argType is nullable
-            if (argType.isMarkedNullable) {
-                invokestatic("kotlinx/serialization/internal/NullableSerializerKt", "makeNullable", // todo: extract?
-                             "(" + kSerializerType.descriptor + ")" + kSerializerType.descriptor, false)
-
-            }
+            if (argType.isMarkedNullable) wrapStackValueIntoNullableSerializer()
             signature.append(kSerializerType.descriptor)
         }
         signature.append(")V")
@@ -256,6 +289,12 @@ internal fun AbstractSerialGenerator.stackValueSerializerInstance(codegen: Class
     return true
 }
 
+fun InstructionAdapter.wrapStackValueIntoNullableSerializer() =
+    invokestatic(
+        "kotlinx/serialization/internal/NullableSerializerKt", "makeNullable",
+        "(" + kSerializerType.descriptor + ")" + kSerializerType.descriptor, false
+    )
+
 //
 // ======= Serializers Resolving =======
 //
@@ -291,11 +330,13 @@ fun AbstractSerialGenerator.getSerialTypeInfo(property: SerializableProperty, ty
                         // reference elements
                         serializer = property.module.findClassAcrossModuleDependencies(referenceArraySerializerId)
                     }
-                // primitive elements are not supported yet
+                    // primitive elements are not supported yet
                 }
             }
-            return JVMSerialTypeInfo(property, Type.getType("Ljava/lang/Object;"),
-                                     if (property.type.isMarkedNullable) "Nullable" else "", serializer)
+            return JVMSerialTypeInfo(
+                property, Type.getType("Ljava/lang/Object;"),
+                if (property.type.isMarkedNullable) "Nullable" else "", serializer
+            )
         }
         OBJECT -> {
             // no explicit serializer for this property. Check other built in types
@@ -312,8 +353,10 @@ fun AbstractSerialGenerator.getSerialTypeInfo(property: SerializableProperty, ty
                     property.descriptor.annotations,
                     property.descriptor.findPsi()
                 )
-            return JVMSerialTypeInfo(property, Type.getType("Ljava/lang/Object;"),
-                                     if (property.type.isMarkedNullable) "Nullable" else "", serializer)
+            return JVMSerialTypeInfo(
+                property, Type.getType("Ljava/lang/Object;"),
+                if (property.type.isMarkedNullable) "Nullable" else "", serializer
+            )
         }
         else -> throw AssertionError("Unexpected sort  for $type") // should not happen
     }

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/SerializerCodegenImpl.kt

@@ -40,6 +40,9 @@ class SerializerCodegenImpl(
     private val serializerAsmType = codegen.typeMapper.mapClass(codegen.descriptor)
     private val serializableAsmType = codegen.typeMapper.mapClass(serializableClass)
 
+    // if we have type parameters, descriptor initializing must be performed in constructor
+    private val staticDescriptor = serializableDescriptor.declaredTypeParameters.isEmpty()
+
     companion object {
         fun generateSerializerExtensions(codegen: ImplementationBodyCodegen) {
             val serializableClass = getSerializableClassDescriptorBySerializer(codegen.descriptor) ?: return
@@ -55,64 +58,86 @@ class SerializerCodegenImpl(
             )
         }
 
-        codegen.generateMethod(typedConstructorDescriptor) { _, _ ->
+        var locals: Int = 0
+        codegen.generateMethod(typedConstructorDescriptor) { _, exprGen ->
             load(0, serializerAsmType)
             invokespecial("java/lang/Object", "<init>", "()V", false)
             serializableDescriptor.declaredTypeParameters.forEachIndexed { i, _ ->
                 load(0, serializerAsmType)
-                load(i+1, kSerializerType)
+                load(++locals, kSerializerType)
                 putfield(serializerAsmType.internalName, "$typeArgPrefix$i", kSerializerType.descriptor)
             }
+            if (!staticDescriptor) exprGen.generateSerialDescriptor(++locals, false)
             areturn(Type.VOID_TYPE)
         }
 
     }
 
-    override fun generateSerialDesc() {
-        codegen.v.newField(OtherOrigin(codegen.myClass.psiOrParent), ACC_PRIVATE or ACC_STATIC or ACC_FINAL or ACC_SYNTHETIC,
-                           serialDescField, descType.descriptor, null, null)
-        // todo: lazy initialization of $$serialDesc that is performed only when save/load is invoked first time
-        val expr = codegen.createOrGetClInitCodegen()
-        with(expr.v) {
-            val classDescVar = 0
-            anew(descImplType)
-            dup()
-            aconst(serialName)
-            invokespecial(descImplType.internalName, "<init>", "(Ljava/lang/String;)V", false)
-            store(classDescVar, descImplType)
-            for (property in orderedProperties) {
-                if (property.transient) continue
-                load(classDescVar, descImplType)
-                aconst(property.name)
-                invokevirtual(descImplType.internalName, CallingConventions.addElement, "(Ljava/lang/String;)V", false)
-                // pushing annotations
-                for ((annotationClass, args, consParams) in property.annotationsWithArguments) {
-                    if (args.size != consParams.size) throw IllegalArgumentException("Can't use arguments with defaults for serializable annotations yet")
-                    load(classDescVar, descImplType)
-                    expr.generateSyntheticAnnotationOnStack(annotationClass, args, consParams)
-                    invokevirtual(
-                        descImplType.internalName,
-                        CallingConventions.addAnnotation,
-                        "(Ljava/lang/annotation/Annotation;)V",
-                        false
-                    )
-                }
-            }
-            // add annotations on class itself
-            for ((annotationClass, args, consParams) in serializableDescriptor.annotationsWithArguments()) {
+    private fun ExpressionCodegen.generateSerialDescriptor(descriptorVar: Int, isStatic: Boolean) = with(v) {
+        anew(descImplType)
+        dup()
+        aconst(serialName)
+        if (isStatic) {
+            assert(serializerDescriptor.kind == ClassKind.OBJECT) { "Serializer for type without type parameters must be an object" }
+            // static descriptor means serializer is an object. it is safer to get it from correct field
+            StackValue.singleton(serializerDescriptor, codegen.typeMapper).put(generatedSerializerType, this)
+        } else {
+            load(0, serializerAsmType)
+        }
+        invokespecial(descImplType.internalName, "<init>", "(Ljava/lang/String;${generatedSerializerType.descriptor})V", false)
+        store(descriptorVar, descImplType)
+        for (property in orderedProperties) {
+            if (property.transient) continue
+            load(descriptorVar, descImplType)
+            aconst(property.name)
+            iconst(if (property.optional) 1 else 0)
+            invokevirtual(descImplType.internalName, CallingConventions.addElement, "(Ljava/lang/String;Z)V", false)
+            // pushing annotations
+            for ((annotationClass, args, consParams) in property.annotationsWithArguments) {
                 if (args.size != consParams.size) throw IllegalArgumentException("Can't use arguments with defaults for serializable annotations yet")
-                load(classDescVar, descImplType)
-                expr.generateSyntheticAnnotationOnStack(annotationClass, args, consParams)
+                load(descriptorVar, descImplType)
+                generateSyntheticAnnotationOnStack(annotationClass, args, consParams)
                 invokevirtual(
                     descImplType.internalName,
-                    CallingConventions.addClassAnnotation,
+                    CallingConventions.addAnnotation,
                     "(Ljava/lang/annotation/Annotation;)V",
                     false
                 )
             }
-            load(classDescVar, descImplType)
-            putstatic(serializerAsmType.internalName, serialDescField, descType.descriptor)
         }
+        // add annotations on class itself
+        for ((annotationClass, args, consParams) in serializableDescriptor.annotationsWithArguments()) {
+            if (args.size != consParams.size) throw IllegalArgumentException("Can't use arguments with defaults for serializable annotations yet")
+            load(descriptorVar, descImplType)
+            generateSyntheticAnnotationOnStack(annotationClass, args, consParams)
+            invokevirtual(
+                descImplType.internalName,
+                CallingConventions.addClassAnnotation,
+                "(Ljava/lang/annotation/Annotation;)V",
+                false
+            )
+        }
+        if (isStatic) {
+            load(descriptorVar, descImplType)
+            putstatic(serializerAsmType.internalName, serialDescField, descType.descriptor)
+        } else {
+            load(0, serializerAsmType)
+            load(descriptorVar, descImplType)
+            putfield(serializerAsmType.internalName, serialDescField, descType.descriptor)
+        }
+    }
+
+    override fun generateSerialDesc() {
+        var flags = ACC_PRIVATE or ACC_FINAL or ACC_SYNTHETIC
+        if (staticDescriptor) flags = flags or ACC_STATIC
+        codegen.v.newField(
+            OtherOrigin(codegen.myClass.psiOrParent), flags,
+            serialDescField, descType.descriptor, null, null
+        )
+        // todo: lazy initialization of $$serialDesc ?
+        if (!staticDescriptor) return
+        val expr = codegen.createOrGetClInitCodegen()
+        expr.generateSerialDescriptor(0, true)
     }
 
     private fun ExpressionCodegen.generateSyntheticAnnotationOnStack(
@@ -139,18 +164,44 @@ class SerializerCodegenImpl(
         }
     }
 
-    private fun InstructionAdapter.serialCLassDescToLocalVar(classDescVar: Int) {
-        getstatic(serializerAsmType.internalName, serialDescField, descType.descriptor)
-        store(classDescVar, descType)
+    // use null to put value on stack, use number to store it to var
+    private fun InstructionAdapter.stackSerialClassDesc(classDescVar: Int?) {
+        if (staticDescriptor)
+            getstatic(serializerAsmType.internalName, serialDescField, descType.descriptor)
+        else {
+            load(0, serializerAsmType)
+            getfield(serializerAsmType.internalName, serialDescField, descType.descriptor)
+        }
+        classDescVar?.let { store(it, descType) }
     }
 
     override fun generateSerializableClassProperty(property: PropertyDescriptor) {
         codegen.generateMethod(property.getter!!) { _, _ ->
-            getstatic(serializerAsmType.internalName, serialDescField, descType.descriptor)
+            stackSerialClassDesc(null)
             areturn(descType)
         }
     }
 
+    override fun generateChildSerializersGetter(function: FunctionDescriptor) {
+        codegen.generateMethod(function) { _, _ ->
+            val size = orderedProperties.size
+            iconst(size)
+            newarray(kSerializerType)
+            for (i in 0 until size) {
+                dup() // array
+                iconst(i) // index
+                val prop = orderedProperties[i]
+                stackValueSerializerInstanceFromSerializerWithoutSti(
+                    codegen,
+                    prop,
+                    this@SerializerCodegenImpl
+                )
+                astore(kSerializerType)
+            }
+            areturn(kSerializerArrayType)
+        }
+    }
+
     override fun generateSave(
             function: FunctionDescriptor
     ) {
@@ -159,7 +210,7 @@ class SerializerCodegenImpl(
             val outputVar = 1
             val objVar = 2
             val descVar = 3
-            serialCLassDescToLocalVar(descVar)
+            stackSerialClassDesc(descVar)
             val objType = signature.valueParameters[1].asmType
             // output = output.writeBegin(classDesc, new KSerializer[0])
             load(outputVar, encoderType)
@@ -236,7 +287,7 @@ class SerializerCodegenImpl(
             val blocksCnt = orderedProperties.size / OPT_MASK_BITS + 1
             fun bitMaskOff(i: Int) = bitMaskBase + (i / OPT_MASK_BITS) * OPT_MASK_TYPE.size
             val propsStartVar = bitMaskBase + OPT_MASK_TYPE.size * blocksCnt
-            serialCLassDescToLocalVar(descVar)
+            stackSerialClassDesc(descVar)
             // boolean readAll = false
             iconst(0)
             store(readAllVar, Type.BOOLEAN_TYPE)

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/KSerializationUtil.kt

@@ -35,21 +35,26 @@ import org.jetbrains.kotlinx.serialization.compiler.resolve.SerializationPackage
 
 
 fun isKSerializer(type: KotlinType?): Boolean =
-        type != null && KotlinBuiltIns.isConstructedFromGivenClass(type, SerialEntityNames.KSERIALIZER_NAME_FQ)
+    type != null && KotlinBuiltIns.isConstructedFromGivenClass(type, SerialEntityNames.KSERIALIZER_NAME_FQ)
+
+fun isGeneratedKSerializer(type: KotlinType?): Boolean =
+    type != null && KotlinBuiltIns.isConstructedFromGivenClass(type, SerialEntityNames.GENERATED_SERIALIZER_FQ)
 
 fun ClassDescriptor.getKSerializerDescriptor(): ClassDescriptor =
-        module.findClassAcrossModuleDependencies(ClassId(packageFqName, SerialEntityNames.KSERIALIZER_NAME))!!
+    module.getClassFromInternalSerializationPackage(SerialEntityNames.GENERATED_SERIALIZER_CLASS.identifier)
 
 
-fun ClassDescriptor.getKSerializerType(argument: SimpleType): SimpleType {
+fun ClassDescriptor.createGeneratedSerializerTypeFor(argument: SimpleType): SimpleType {
     val projectionType = Variance.INVARIANT
     val types = listOf(TypeProjectionImpl(projectionType, argument))
     return KotlinTypeFactory.simpleNotNullType(Annotations.EMPTY, getKSerializerDescriptor(), types)
 }
 
 internal fun extractKSerializerArgumentFromImplementation(implementationClass: ClassDescriptor): KotlinType? {
-    val kSerializerSupertype = implementationClass.typeConstructor.supertypes
-        .find { isKSerializer(it) } ?: return null
+    val supertypes = implementationClass.typeConstructor.supertypes
+    val kSerializerSupertype = supertypes.find { isGeneratedKSerializer(it) }
+        ?: supertypes.find { isKSerializer(it) }
+        ?: return null
     return kSerializerSupertype.arguments.first().type
 }
 
@@ -140,7 +145,11 @@ fun getSerializableClassDescriptorByCompanion(thisDescriptor: ClassDescriptor):
 fun getSerializableClassDescriptorBySerializer(serializerDescriptor: ClassDescriptor): ClassDescriptor? {
     val serializerForClass = serializerDescriptor.annotations.serializerForClass
     if (serializerForClass != null) return serializerForClass.toClassDescriptor
-    if (serializerDescriptor.name != SerialEntityNames.SERIALIZER_CLASS_NAME) return null
+    if (serializerDescriptor.name !in setOf(
+            SerialEntityNames.SERIALIZER_CLASS_NAME,
+            SerialEntityNames.GENERATED_SERIALIZER_CLASS
+        )
+    ) return null
     val classDescriptor = (serializerDescriptor.containingDeclaration as? ClassDescriptor) ?: return null
     if (!classDescriptor.isInternalSerializable) return null
     return classDescriptor
@@ -187,7 +196,7 @@ private fun ModuleDescriptor.getFromPackage(packageFqName: FqName, classSimpleNa
             Name.identifier(classSimpleName)
         )
     )
-) { "Can't locate class $classSimpleName" }
+) { "Can't locate class $classSimpleName from package $packageFqName" }
 
 fun ClassDescriptor.getClassFromSerializationPackage(classSimpleName: String) =
         requireNotNull(module.findClassAcrossModuleDependencies(ClassId(packageFqName, Name.identifier(classSimpleName)))) {"Can't locate class $classSimpleName"}

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/KSerializerDescriptorResolver.kt

@@ -57,7 +57,7 @@ object KSerializerDescriptorResolver {
     fun addSerializerSupertypes(classDescriptor: ClassDescriptor, supertypes: MutableList<KotlinType>) {
         val serializableClassDescriptor = getSerializableClassDescriptorBySerializer(classDescriptor) ?: return
         if (supertypes.none(::isKSerializer)) {
-            supertypes.add(classDescriptor.getKSerializerType(serializableClassDescriptor.defaultType))
+            supertypes.add(classDescriptor.createGeneratedSerializerTypeFor(serializableClassDescriptor.defaultType))
         }
     }
 
@@ -157,16 +157,15 @@ object KSerializerDescriptorResolver {
                     fromSupertypes.none { checkParameters(it) && it.modality == Modality.FINAL }
         }
 
-        if (name == SerialEntityNames.SAVE_NAME &&
-            shouldAddSerializerFunction { classDescriptor.checkSaveMethodParameters(it.valueParameters) }
-        ) {
-            result.add(createSaveFunctionDescriptor(thisDescriptor))
-        }
+        val isSave = name == SerialEntityNames.SAVE_NAME &&
+                shouldAddSerializerFunction { classDescriptor.checkSaveMethodParameters(it.valueParameters) }
+        val isLoad = name == SerialEntityNames.LOAD_NAME &&
+                shouldAddSerializerFunction { classDescriptor.checkLoadMethodParameters(it.valueParameters) }
+        val isDescriptorGetter = name == SerialEntityNames.GENERATED_DESCRIPTOR_GETTER &&
+                shouldAddSerializerFunction { true /* TODO? */ }
 
-        if (name == SerialEntityNames.LOAD_NAME &&
-            shouldAddSerializerFunction { classDescriptor.checkLoadMethodParameters(it.valueParameters) }
-        ) {
-            result.add(createLoadFunctionDescriptor(thisDescriptor))
+        if (isSave || isLoad || isDescriptorGetter) {
+            result.add(doCreateSerializerFunction(thisDescriptor, name))
         }
     }
 
@@ -176,12 +175,6 @@ object KSerializerDescriptorResolver {
     ): PropertyDescriptor =
         doCreateSerializerProperty(companionDescriptor, classDescriptor, SerialEntityNames.SERIAL_DESC_FIELD_NAME)
 
-    fun createSaveFunctionDescriptor(companionDescriptor: ClassDescriptor): SimpleFunctionDescriptor =
-        doCreateSerializerFunction(companionDescriptor, SerialEntityNames.SAVE_NAME)
-
-    fun createLoadFunctionDescriptor(companionDescriptor: ClassDescriptor): SimpleFunctionDescriptor =
-        doCreateSerializerFunction(companionDescriptor, SerialEntityNames.LOAD_NAME)
-
     private fun doCreateSerializerProperty(
         companionDescriptor: ClassDescriptor,
         classDescriptor: ClassDescriptor,

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/NamingConventions.kt

@@ -38,6 +38,9 @@ object SerialEntityNames {
     val SERIALIZER_CLASS_NAME = Name.identifier(SERIALIZER_CLASS)
     val IMPL_NAME = Name.identifier("Impl")
 
+    val GENERATED_SERIALIZER_CLASS = Name.identifier("GeneratedSerializer")
+    val GENERATED_SERIALIZER_FQ = SerializationPackages.internalPackageFqName.child(GENERATED_SERIALIZER_CLASS)
+
     const val ENCODER_CLASS = "Encoder"
     const val STRUCTURE_ENCODER_CLASS = "CompositeEncoder"
     const val DECODER_CLASS = "Decoder"
@@ -58,6 +61,7 @@ object SerialEntityNames {
     val SERIAL_DESC_FIELD_NAME = Name.identifier(SERIAL_DESC_FIELD)
     val SAVE_NAME = Name.identifier(SAVE)
     val LOAD_NAME = Name.identifier(LOAD)
+    val GENERATED_DESCRIPTOR_GETTER = Name.identifier("childSerializers")
     val WRITE_SELF_NAME = Name.identifier("write\$Self")
     val SERIALIZER_PROVIDER_NAME = Name.identifier("serializer")