Fix #12

dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/FrontMatterEnvelopeFormat.kt

@@ -2,13 +2,11 @@ package hep.dataforge.io.yaml
 
 import hep.dataforge.context.Context
 import hep.dataforge.io.*
-import hep.dataforge.meta.EmptyMeta
+import hep.dataforge.meta.*
-import hep.dataforge.meta.Meta
-import hep.dataforge.meta.get
-import hep.dataforge.meta.string
 import kotlinx.io.core.*
 import kotlinx.serialization.toUtf8Bytes
 
+@DFExperimental
 class FrontMatterEnvelopeFormat(
     val io: IOPlugin,
     val metaType: String = YamlMetaFormat.name.toString(),

dataforge-io/dataforge-io-yaml/src/main/kotlin/hep/dataforge/io/yaml/YamlMetaFormat.kt

@@ -4,6 +4,7 @@ import hep.dataforge.context.Context
 import hep.dataforge.descriptors.NodeDescriptor
 import hep.dataforge.io.MetaFormat
 import hep.dataforge.io.MetaFormatFactory
+import hep.dataforge.meta.DFExperimental
 import hep.dataforge.meta.Meta
 import hep.dataforge.meta.toMap
 import hep.dataforge.meta.toMeta
@@ -29,6 +30,7 @@ private class InputAsStream(val input: Input) : InputStream() {
 
 private fun Input.asStream() = InputAsStream(this)
 
+@DFExperimental
 class YamlMetaFormat(val meta: Meta) : MetaFormat {
     private val yaml = Yaml()
 

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/configDelegates.kt

@@ -117,11 +117,11 @@ fun <T : Specific> Configurable.spec(builder: (Config) -> T, key: Name? = null)
  * Extra delegates for special cases
  */
 
-fun Configurable.stringList(key: Name? = null): ReadWriteDelegateWrapper<Value?, List<String>> =
+fun Configurable.stringList(vararg strings: String, key: Name? = null): ReadWriteDelegateWrapper<Value?, List<String>> =
-    value(emptyList(), key) { it?.list?.map { value -> value.string } ?: emptyList() }
+    value(strings.asList(), key) { it?.list?.map { value -> value.string } ?: emptyList() }
 
-fun Configurable.numberList(key: Name? = null): ReadWriteDelegateWrapper<Value?, List<Number>> =
+fun Configurable.numberList(vararg numbers: Number, key: Name? = null): ReadWriteDelegateWrapper<Value?, List<Number>> =
-    value(emptyList(), key) { it?.list?.map { value -> value.number } ?: emptyList() }
+    value(numbers.asList(), key) { it?.list?.map { value -> value.number } ?: emptyList() }
 
 /**
  * A special delegate for double arrays

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/mapMeta.kt

@@ -14,6 +14,7 @@ import hep.dataforge.values.Value
 /**
  * Convert meta to map of maps
  */
+@DFExperimental
 fun Meta.toMap(descriptor: NodeDescriptor? = null): Map<String, Any?> {
     return items.entries.associate { (token, item) ->
         token.toString() to when (item) {
@@ -26,6 +27,7 @@ fun Meta.toMap(descriptor: NodeDescriptor? = null): Map<String, Any?> {
 /**
  * Convert map of maps to meta
  */
+@DFExperimental
 fun Map<String, Any?>.toMeta(descriptor: NodeDescriptor? = null): Meta = buildMeta {
     entries.forEach { (key, value) ->
         @Suppress("UNCHECKED_CAST")

dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/Value.kt

@@ -41,7 +41,7 @@ interface Value {
      * get this value represented as List
      */
     val list: List<Value>
-        get() = listOf(this)
+        get() = if(this == Null) emptyList() else listOf(this)
 
     override fun equals(other: Any?): Boolean
 
@@ -60,7 +60,14 @@ interface Value {
                 true -> True
                 false -> False
                 is Number -> value.asValue()
-                is Iterable<*> -> ListValue(value.map { of(it) })
+                is Iterable<*> -> {
+                    val list = value.map { of(it) }
+                    if (list.isEmpty()) {
+                        Null
+                    } else {
+                        ListValue(list)
+                    }
+                }
                 is DoubleArray -> value.asValue()
                 is IntArray -> value.asValue()
                 is FloatArray -> value.asValue()
@@ -174,9 +181,7 @@ class EnumValue<E : Enum<*>>(override val value: E) : Value {
 
 class ListValue(override val list: List<Value>) : Value {
     init {
-        if (list.isEmpty()) {
+        require(list.isNotEmpty()) { "Can't create list value from empty list" }
-            throw IllegalArgumentException("Can't create list value from empty list")
-        }
     }
 
     override val value: List<Value> get() = list
@@ -208,17 +213,20 @@ fun Boolean.asValue(): Value = if (this) True else False
 
 fun String.asValue(): Value = StringValue(this)
 
-fun Iterable<Value>.asValue(): Value = ListValue(this.toList())
+fun Iterable<Value>.asValue(): Value {
+    val list = toList()
+    return if (list.isEmpty()) Null else ListValue(this.toList())
+}
 
-fun IntArray.asValue(): Value = ListValue(map { NumberValue(it) })
+fun IntArray.asValue(): Value = if (isEmpty()) Null else ListValue(map { NumberValue(it) })
 
-fun LongArray.asValue(): Value = ListValue(map { NumberValue(it) })
+fun LongArray.asValue(): Value = if (isEmpty()) Null else ListValue(map { NumberValue(it) })
 
-fun ShortArray.asValue(): Value = ListValue(map { NumberValue(it) })
+fun ShortArray.asValue(): Value = if (isEmpty()) Null else ListValue(map { NumberValue(it) })
 
-fun FloatArray.asValue(): Value = ListValue(map { NumberValue(it) })
+fun FloatArray.asValue(): Value = if (isEmpty()) Null else ListValue(map { NumberValue(it) })
 
-fun ByteArray.asValue(): Value = ListValue(map { NumberValue(it) })
+fun ByteArray.asValue(): Value = if (isEmpty()) Null else ListValue(map { NumberValue(it) })
 
 
 /**

dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/exoticValues.kt

@@ -46,4 +46,4 @@ class DoubleArrayValue(override val value: DoubleArray) : Value {
     override fun toString(): String = list.joinToString (prefix = "[", postfix = "]")
 }
 
-fun DoubleArray.asValue(): DoubleArrayValue = DoubleArrayValue(this)
+fun DoubleArray.asValue(): Value = if(isEmpty()) Null else DoubleArrayValue(this)

dataforge-meta/src/commonTest/kotlin/hep/dataforge/meta/SpecificationTest.kt

@@ -0,0 +1,23 @@
+package hep.dataforge.meta
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class SpecificationTest {
+    class TestSpecific(override val config: Config) : Specific {
+        var list by numberList(1, 2, 3)
+
+        companion object : Specification<TestSpecific> {
+            override fun wrap(config: Config): TestSpecific = TestSpecific(config)
+        }
+    }
+
+
+    @Test
+    fun testSpecific(){
+        val testObject = TestSpecific.build {
+            list = emptyList()
+        }
+        assertEquals(emptyList(), testObject.list)
+    }
+}