Added tests on calculated default value of properties depending on other properties

Tests for internal and external serializable classes. The default values for constructor properties, transient properties, body properties are checked

Author: shanshin

formats/json/build.gradle

@@ -24,3 +24,7 @@ kotlin {
         }
     }
 }
+
+compileTestKotlinJsLegacy {
+    exclude '**/PropertyInitializerTest.kt'
+}

formats/json/commonTest/src/kotlinx/serialization/features/PropertyInitializerTest.kt

@@ -0,0 +1,105 @@
+@file:Suppress("MayBeConstant")
+
+package kotlinx.serialization.features
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.Json
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+internal val globalVar: Int = 4
+
+internal fun globalFun(): Int {
+    return 7
+}
+
+internal const val PROPERTY_INITIALIZER_JSON = """{
+    "valProperty": 1,
+    "varProperty": 2,
+    "literalConst": 3,
+    "globalVarRef": 4,
+    "computed": 5,
+    "doubleRef": 6,
+    "globalFun": 7,
+    "globalFunExpr": 8,
+    "itExpr": 9,
+    "transientRefFromProp": 10,
+    "bodyProp": 11,
+    "dependBodyProp": 12,
+    "getterDepend": 13
+}"""
+
+@Suppress("MemberVisibilityCanBePrivate", "unused", "ComplexRedundantLet")
+class PropertyInitializerTest {
+    @Serializable
+    data class InternalClass(
+        val valProperty: Int,
+        var varProperty: Int,
+        val literalConst: Int = 3,
+        val globalVarRef: Int = globalVar,
+        val computed: Int = valProperty + varProperty + 2,
+        val doubleRef: Int = literalConst + literalConst,
+        var globalFun: Int = globalFun(),
+        var globalFunExpr: Int = globalFun() + 1,
+        val itExpr: Int = literalConst.let { it + 6 },
+        @Transient val constTransient: Int = 6,
+        @Transient val serializedRefTransient: Int = varProperty + 1,
+        @Transient val refTransient: Int = serializedRefTransient,
+        val transientRefFromProp: Int = constTransient + 4,
+    ) {
+        val valGetter: Int get() { return 5 }
+        var bodyProp: Int = 11
+        var dependBodyProp: Int = bodyProp + 1
+        var getterDepend: Int = valGetter + 8
+    }
+
+    private val format = Json { encodeDefaults = true; prettyPrint = true }
+
+    data class ExternalClass(
+        val valProperty: Int,
+        var varProperty: Int,
+        val literalConst: Int = 3,
+        val globalVarRef: Int = globalVar,
+        val computed: Int = valProperty + varProperty + 2,
+        val doubleRef: Int = literalConst + literalConst,
+        var globalFun: Int = globalFun(),
+        var globalFunExpr: Int = globalFun() + 1,
+        val itExpr: Int = literalConst.let { it + 6 },
+        @Transient val constTransient: Int = 6,
+        @Transient val serializedRefTransient: Int = varProperty + 1,
+        @Transient val refTransient: Int = serializedRefTransient,
+        val transientRefFromProp: Int = constTransient + 4,
+    ) {
+        val valGetter: Int get() { return 5 }
+        var bodyProp: Int = 11
+        var dependBodyProp: Int = bodyProp + 1
+        var getterDepend: Int = valGetter + 8
+    }
+
+    @Serializer(ExternalClass::class)
+    object ExternalSerializer
+
+    @Test
+    fun testInternalSerializeDefault() {
+        val encoded = format.encodeToString(InternalClass(1, 2))
+        assertEquals(PROPERTY_INITIALIZER_JSON, encoded)
+    }
+
+    @Test
+    fun testInternalDeserializeDefault() {
+        val decoded = format.decodeFromString<InternalClass>("""{"valProperty": 5, "varProperty": 6}""")
+        assertEquals(InternalClass(5, 6), decoded)
+    }
+
+    @Test
+    fun testExternalSerializeDefault() {
+        val encoded = format.encodeToString(ExternalSerializer, ExternalClass(1, 2))
+        assertEquals(PROPERTY_INITIALIZER_JSON, encoded)
+    }
+
+    @Test
+    fun testExternalDeserializeDefault() {
+        val decoded = format.decodeFromString(ExternalSerializer,"""{"valProperty": 5, "varProperty": 6}""")
+        assertEquals(ExternalClass(5, 6), decoded)
+    }
+}