optional descriptor for descriptor builder

dataforge-io/src/commonMain/kotlin/hep/dataforge/io/serialization/MetaSerializer.kt

@@ -1,6 +1,7 @@
-package hep.dataforge.io
+package hep.dataforge.io.serialization
 
-import hep.dataforge.io.serialization.descriptor
+import hep.dataforge.io.toJson
+import hep.dataforge.io.toMeta
 import hep.dataforge.meta.*
 import hep.dataforge.names.NameToken
 import hep.dataforge.values.*
@@ -16,10 +17,10 @@ object ValueSerializer : KSerializer<Value> {
     private val valueTypeSerializer = EnumSerializer(ValueType::class)
     private val listSerializer by lazy { ArrayListSerializer(ValueSerializer) }
 
-    override val descriptor: SerialDescriptor = descriptor("Value") {
+    override val descriptor: SerialDescriptor = descriptor("hep.dataforge.values.Value") {
         boolean("isList")
         enum<ValueType>("valueType")
-        element("value", PolymorphicClassDescriptor)
+        element("value", null)
     }
 
     private fun Decoder.decodeValue(): Value {
@@ -69,7 +70,7 @@ object ValueSerializer : KSerializer<Value> {
 object MetaItemSerializer : KSerializer<MetaItem<*>> {
     override val descriptor: SerialDescriptor = descriptor("MetaItem") {
         boolean("isNode")
-        element("value", PolymorphicClassDescriptor)
+        element("value", null)
     }
 
 
@@ -93,17 +94,21 @@ object MetaItemSerializer : KSerializer<MetaItem<*>> {
 
 private class DeserializedMeta(override val items: Map<NameToken, MetaItem<*>>) : MetaBase()
 
-
 /**
  * Serialized for meta
  */
 @Serializer(Meta::class)
 object MetaSerializer : KSerializer<Meta> {
-    private val mapSerializer =
-        HashMapSerializer(StringSerializer, MetaItemSerializer)
+    private val mapSerializer = HashMapSerializer(
+        StringSerializer,
+        MetaItemSerializer
+    )
 
-    override val descriptor: SerialDescriptor =
-        NamedMapClassDescriptor("Meta", StringSerializer.descriptor, MetaItemSerializer.descriptor)
+    override val descriptor: SerialDescriptor = NamedMapClassDescriptor(
+        "hep.dataforge.meta.Meta",
+        StringSerializer.descriptor,
+        MetaItemSerializer.descriptor
+    )
 
     override fun deserialize(decoder: Decoder): Meta {
         return if (decoder is JsonInput) {

dataforge-io/src/commonMain/kotlin/hep/dataforge/io/serialization/serializationUtils.kt

@@ -12,12 +12,12 @@ import kotlinx.serialization.internal.*
 inline class SerialDescriptorBuilder(private val impl: SerialClassDescImpl) {
     fun element(
         name: String,
-        descriptor: SerialDescriptor,
+        descriptor: SerialDescriptor?,
         isOptional: Boolean = false,
         vararg annotations: Annotation
     ) {
         impl.addElement(name, isOptional)
-        impl.pushDescriptor(descriptor)
+        descriptor?.let { impl.pushDescriptor(descriptor) }
         annotations.forEach {
             impl.pushAnnotation(it)
         }
@@ -65,7 +65,10 @@ inline class SerialDescriptorBuilder(private val impl: SerialClassDescImpl) {
     fun build(): SerialDescriptor = impl
 }
 
-inline fun KSerializer<*>.descriptor(name: String, block: SerialDescriptorBuilder.() -> Unit): SerialDescriptor =
+inline fun <reified T : Any> KSerializer<T>.descriptor(
+    name: String,
+    block: SerialDescriptorBuilder.() -> Unit
+): SerialDescriptor =
     SerialDescriptorBuilder(SerialClassDescImpl(name)).apply(block).build()
 
 fun Decoder.decodeStructure(

dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MetaSerializerTest.kt

@@ -1,5 +1,7 @@
 package hep.dataforge.io
 
+import hep.dataforge.io.serialization.MetaItemSerializer
+import hep.dataforge.io.serialization.MetaSerializer
 import hep.dataforge.io.serialization.NameSerializer
 import hep.dataforge.meta.buildMeta
 import hep.dataforge.names.toName