Add encoding value classes

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/encoders/TomlAbstractEncoder.kt

@@ -15,6 +15,7 @@ import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerializationStrategy
 import kotlinx.serialization.descriptors.*
 import kotlinx.serialization.encoding.AbstractEncoder
+import kotlinx.serialization.encoding.Encoder
 import kotlinx.serialization.modules.SerializersModule
 
 /**
@@ -104,6 +105,12 @@ public abstract class TomlAbstractEncoder protected constructor(
         appendValue(TomlNull())
     }
 
+    override fun encodeInline(descriptor: SerialDescriptor): Encoder {
+        // Value (inline) class always has one element
+        encodeElement(descriptor, 0)
+        return this
+    }
+
     override fun encodeString(value: String) {
         if (!encodeAsKey(value)) {
             appendValue(
@@ -126,7 +133,9 @@ public abstract class TomlAbstractEncoder protected constructor(
             }
             else -> when (val kind = desc.kind) {
                 is StructureKind,
-                is PolymorphicKind -> if (!encodeAsKey(value as Any, desc.serialName)) {
+                is PolymorphicKind -> if (desc.isInline) {
+                    serializer.serialize(this, value)
+                } else if (!encodeAsKey(value as Any, desc.serialName)) {
                     val encoder = encodeStructure(kind)
 
                     serializer.serialize(encoder, value)
@@ -204,7 +213,15 @@ public abstract class TomlAbstractEncoder protected constructor(
 
     protected open fun isNextElementKey(descriptor: SerialDescriptor, index: Int): Boolean {
         when (val kind = descriptor.kind) {
-            StructureKind.CLASS -> setKey(descriptor.getElementName(index))
+            StructureKind.CLASS -> {
+                // We should keep previous key when we have value (inline) class
+                // But if key is null, it means that value class isn't nested, and we have to use its own key
+                if (descriptor.isInline && attributes.key != null) {
+                    // do nothing
+                } else {
+                    setKey(descriptor.getElementName(index))
+                }
+            }
             StructureKind.MAP -> {
                 // When the index is even (key) mark the next element as a key and
                 // skip annotations and element index incrementing.

ktoml-core/src/commonTest/kotlin/com/akuleshov7/ktoml/encoders/ValueClassEncoderTest.kt

@@ -0,0 +1,159 @@
+package com.akuleshov7.ktoml.encoders
+
+import com.akuleshov7.ktoml.Toml
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.encodeToString
+import kotlin.jvm.JvmInline
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class ValueClassEncoderTest {
+
+    @Serializable
+    @JvmInline
+    value class Color(val rgb: Int)
+
+    @Serializable
+    data class NamedColor(val color: Color, val name: String)
+
+    @Test
+    fun testForSimpleValueClass() {
+        val color = Color(15)
+        val result = Toml.encodeToString(color)
+
+        assertEquals("rgb = 15", result)
+    }
+
+    @Test
+    fun testForNestedValueClass() {
+        val namedColor = NamedColor(
+            Color(150),
+            "black"
+        )
+
+        val result = Toml.encodeToString(namedColor)
+        assertEquals(
+            """
+                color = 150
+                name = "black"
+            """.trimIndent(),
+            result
+        )
+    }
+
+    @Test
+    fun testForLisOfValueClass() {
+        @Serializable
+        class Palette(val colors: List<Color>)
+        val palette = Palette(
+            listOf(
+                Color(0),
+                Color(255),
+                Color(128),
+            )
+        )
+
+        val result = Toml.encodeToString(palette)
+        assertEquals("colors = [ 0, 255, 128 ]", result)
+    }
+
+    @Serializable
+    @JvmInline
+    value class Num(val int: Int)
+
+    @Serializable
+    data class Nums(
+        val num1: Num,
+        val num2: Num,
+    )
+
+    @Test
+    fun testForMultipleValueClass() {
+        val nums = Nums(
+            num1 = Num(5),
+            num2 = Num(111)
+        )
+        val result = Toml.encodeToString(nums)
+
+        assertEquals(
+            """
+                num1 = 5
+                num2 = 111
+            """.trimIndent(),
+            result
+        )
+    }
+
+    @Serializable
+    data class MyObject(
+        val height: Int,
+        val width: Int
+    )
+
+    @Serializable
+    @JvmInline
+    value class Info(val obj: MyObject)
+
+    @Serializable
+    data class InfoWrapper(
+        val metaInfo1: Int,
+        val info: Info,
+        val metaInfo2: String
+    )
+
+    @Test
+    fun testForValueClassWithObjectInside() {
+        val obj = InfoWrapper(
+            metaInfo1 = 1,
+            info = Info(MyObject(10, 20)),
+            metaInfo2 = "test"
+        )
+        val result = Toml.encodeToString(obj)
+
+        assertEquals(
+            """
+                metaInfo1 = 1
+                metaInfo2 = "test"
+
+                [info]
+                    height = 10
+                    width = 20
+            """.trimIndent(),
+            result
+        )
+    }
+
+    @Serializable
+    @JvmInline
+    value class AnotherInfoWrapper(val info: Info)
+
+    @Test
+    fun testForValueClassInsideValueClass() {
+        val obj = AnotherInfoWrapper(Info(MyObject(10, 20)))
+        val result = Toml.encodeToString(obj)
+
+        assertEquals(
+            """
+                [info]
+                    height = 10
+                    width = 20
+            """.trimIndent(),
+            result
+        )
+    }
+
+    @Test
+    fun testDataClassInsideValueClass() {
+        val obj = Info(MyObject(32, 64))
+        val result = Toml.encodeToString(obj)
+
+        assertEquals(
+            """
+                [obj]
+                    height = 32
+                    width = 64
+            """.trimIndent(),
+            result
+        )
+    }
+}