#911 kotlinx.serialization DocumentDecoder List element index fix (#913)

Author: Niro

potassium-nitrite/src/main/kotlin/org/dizitart/kno2/serialization/DocumentDecoder.kt

@@ -119,13 +119,14 @@ internal class DocumentDecoder(private val document: Document, descriptor: Seria
 @OptIn(ExperimentalSerializationApi::class)
 private class ListDecoder(private val list: ArrayDeque<Any>) : AbstractDecoder() {
     private var elementIndex = 0
+    private val initialSize = list.size
 
     override val serializersModule: SerializersModule = EmptySerializersModule()
 
     override fun decodeValue(): Any = list.removeFirst()
 
     override fun decodeElementIndex(descriptor: SerialDescriptor): Int {
-        if (list.isEmpty() || elementIndex == descriptor.elementsCount) return CompositeDecoder.DECODE_DONE
+        if (list.isEmpty() || elementIndex == initialSize) return CompositeDecoder.DECODE_DONE
         return elementIndex++
     }
 

potassium-nitrite/src/test/kotlin/org/dizitart/kno2/KotlinXSerializationMapperTest.kt

@@ -124,6 +124,20 @@ class KotlinXSerializationMapperTest {
                 emptyList(),
                 emptyArray(),
             ),
+            TestData(
+                TestData.SomePolymorphType.SomeTypeB("someValue"),
+                emptyMap(),
+                emptyMap(),
+                TestData.InnerObject(""),
+                "",
+                TestData.SomeValueClass("someString"),
+                1,
+                1.0,
+                "test",
+                TestData.SomeEnum.SomeValue,
+                emptyList(),
+                emptyArray(),
+            ),
         ),
         valueClass = TestData.SomeValueClass("someString"),
         someArray = arrayOf("someArrayData"),