From 66355793ee0a5143be296a353bb45f4d39aaf11e Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Thu, 28 Jan 2021 10:34:28 +0300
Subject: [PATCH] Remove restriction on empty ListValue since it have a
 separate type now.

---
 .../kotlin/hep/dataforge/io/MetaFormatTest.kt | 24 +++++++++++++++++++
 .../kotlin/hep/dataforge/values/Value.kt      |  8 +++----
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MetaFormatTest.kt b/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MetaFormatTest.kt
index af33cfde..9e71a907 100644
--- a/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MetaFormatTest.kt
+++ b/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MetaFormatTest.kt
@@ -2,6 +2,7 @@ package hep.dataforge.io
 
 import hep.dataforge.meta.*
 import hep.dataforge.meta.JsonMeta.Companion.JSON_ARRAY_KEY
+import hep.dataforge.values.ListValue
 import hep.dataforge.values.number
 import kotlinx.io.asBinary
 import kotlinx.serialization.json.*
@@ -79,4 +80,27 @@ class MetaFormatTest {
         assertEquals(listOf(1.0, 2.0, 3.0), meta["$JSON_ARRAY_KEY[2"].value?.list?.map { it.number.toDouble() })
     }
 
+    @Test
+    fun testJsonStringToMeta(){
+        val jsonString = """
+            {
+                "comments": [
+                ],
+                "end_time": "2018-04-13T22:01:46",
+                "format_description": "https://docs.google.com/document/d/12qmnZRO55y6zr08Wf-BQYAmklqgf5y3j_gD_VkNscXc/edit?usp=sharing",
+                "iteration_info": {
+                    "iteration": 4,
+                    "reverse": false
+                },
+                "operator": "Vasiliy",
+                "programm_revision": "1.1.1-79-g7c0cad6",
+                "start_time": "2018-04-13T21:42:04",
+                "type": "info_file"
+            }
+        """.trimIndent()
+        val json = Json.parseToJsonElement(jsonString)
+        val meta = json.toMetaItem().node!!
+        assertEquals(ListValue.EMPTY, meta["comments"].value)
+    }
+
 }
\ No newline at end of file
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/Value.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/Value.kt
index 676f7134..73b1318c 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/Value.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/values/Value.kt
@@ -179,10 +179,6 @@ public class EnumValue<E : Enum<*>>(override val value: E) : Value {
 }
 
 public class ListValue(override val list: List<Value>) : Value, Iterable<Value> {
-    init {
-        require(list.isNotEmpty()) { "Can't create list value from empty list" }
-    }
-
     override val value: List<Value> get() = list
     override val type: ValueType get() = ValueType.LIST
 
@@ -202,6 +198,10 @@ public class ListValue(override val list: List<Value>) : Value, Iterable<Value>
     override fun hashCode(): Int {
         return list.hashCode()
     }
+
+    public companion object{
+        public val EMPTY: ListValue = ListValue(emptyList())
+    }
 }
 
 public fun Number.asValue(): Value = NumberValue(this)