Fix dynamic serialization for nullable values

formats/json/jsMain/src/kotlinx/serialization/json/Dynamics.kt

@@ -49,7 +49,6 @@ public inline fun <reified T> Json.decodeFromDynamic(dynamic: dynamic): T =
  *
  * Limitations:
  * * Map keys must be of primitive or enum type
- * * Currently does not support polymorphism
  * * All [Long] values must be less than [`abs(2^53-1)`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER).
  * Otherwise, they're encoded as doubles with precision loss and require `isLenient` flag of [Json.configuration] set to true.
  *

formats/json/jsMain/src/kotlinx/serialization/json/internal/DynamicDecoders.kt

@@ -49,6 +49,10 @@ private open class DynamicInput(
  return json.decodeFromDynamic(JsonElement.serializer(), value[tag])
  }
 
+ if (value == null) {
+ return JsonNull
+ }
+
  val keys: dynamic = js("Object").keys(value)
  val size: Int = keys.length as Int
  return buildJsonObject {

formats/json/jsTest/src/kotlinx/serialization/json/DecodeFromDynamicSpecialCasesTest.kt

@@ -79,6 +79,12 @@ class DecodeFromDynamicSpecialCasesTest {
  testJsonElement<JsonPrimitive>(js(""""42""""), JsonPrimitive("42"))
  }
 
+ @Test
+ fun testJsonNull() {
+ testJsonElement<JsonElement>(js("null"), JsonNull)
+ testJsonElement<JsonElement>(js("undefined"), JsonNull)
+ }
+
  @Test
  fun testJsonArray() {
  testJsonElement<JsonElement>(js("[1,2,3]"), JsonArray((1..3).map(::JsonPrimitive)))
@@ -103,13 +109,13 @@ class DecodeFromDynamicSpecialCasesTest {
  }
 
  @Serializable
- data class Wrapper(val e: JsonElement, val p: JsonPrimitive, val o: JsonObject, val a: JsonArray)
+ data class Wrapper(val e: JsonElement, val p: JsonPrimitive, val o: JsonObject, val a: JsonArray, val n: JsonNull)
 
  @Test
  fun testJsonElementWrapper() {
- val js = js("""{"e":42,"p":"239", "o":{"k":"v"}, "a":[1, 2, 3]}""")
+ val js = js("""{"e":42,"p":"239", "o":{"k":"v"}, "a":[1, 2, 3], "n": null}""")
  val parsed = Json.decodeFromDynamic<Wrapper>(js)
- val expected = Wrapper(JsonPrimitive(42), JsonPrimitive("239"), buildJsonObject { put("k", "v") }, JsonArray((1..3).map(::JsonPrimitive)))
+ val expected = Wrapper(JsonPrimitive(42), JsonPrimitive("239"), buildJsonObject { put("k", "v") }, JsonArray((1..3).map(::JsonPrimitive)), JsonNull)
  assertEquals(expected, parsed)
  }
 }

formats/json/jsTest/src/kotlinx/serialization/json/DynamicPolymorphismTest.kt

@@ -21,6 +21,18 @@ class DynamicPolymorphismTest {
  @Serializable
  @SerialName("type_child")
  data class TypeChild(val type: String) : Sealed(2)
+
+ @Serializable
+ @SerialName("nullable_child")
+ data class NullableChild(val nullable: String?): Sealed(3)
+
+ @Serializable
+ @SerialName("list_child")
+ data class ListChild(val list: List<String>): Sealed(4)
+
+ @Serializable
+ @SerialName("default_child")
+ data class DefaultChild(val default: String? = "default"): Sealed(5)
  }
 
  @Serializable
@@ -103,6 +115,135 @@ class DynamicPolymorphismTest {
  }
  }
 
+ @Test
+ fun testNullable() {
+ val nonNullChild = Sealed.NullableChild("nonnull")
+ encodeAndDecode(Sealed.serializer(), nonNullChild, arrayJson) {
+ assertEquals("nullable_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(nonNullChild.nullable, dynamicValue.nullable)
+ assertEquals(nonNullChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+ encodeAndDecode(Sealed.serializer(), nonNullChild, objectJson) {
+ assertEquals("nullable_child", this.type)
+ assertEquals(nonNullChild.nullable, this.nullable)
+ assertEquals(nonNullChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+
+ val nullChild = Sealed.NullableChild(null)
+ encodeAndDecode(Sealed.serializer(), nullChild, arrayJson) {
+ assertEquals("nullable_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(nullChild.nullable, dynamicValue.nullable)
+ assertEquals(nullChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+ encodeAndDecode(Sealed.serializer(), nullChild, objectJson) {
+ assertEquals("nullable_child", this.type)
+ assertEquals(nullChild.nullable, this.nullable)
+ assertEquals(nullChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+ }
+
+ @Test
+ fun testList() {
+ val listChild = Sealed.ListChild(listOf("one", "two"))
+ encodeAndDecode(Sealed.serializer(), listChild, arrayJson) {
+ assertEquals("list_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(listChild.list, (dynamicValue.list as Array<String>).toList())
+ assertEquals(listChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+ encodeAndDecode(Sealed.serializer(), listChild, objectJson) {
+ assertEquals("list_child", this.type)
+ assertEquals(listChild.list, (this.list as Array<String>).toList())
+ assertEquals(listChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+ }
+
+ @Test
+ fun testEmptyList() {
+ val emptyListChild = Sealed.ListChild(emptyList())
+ encodeAndDecode(Sealed.serializer(), emptyListChild, arrayJson) {
+ assertEquals("list_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(emptyListChild.list, (dynamicValue.list as Array<String>).toList())
+ assertEquals(emptyListChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+ encodeAndDecode(Sealed.serializer(), emptyListChild, objectJson) {
+ assertEquals("list_child", this.type)
+ assertEquals(emptyListChild.list, (this.list as Array<String>).toList())
+ assertEquals(emptyListChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+ }
+
+ @Test
+ fun testDefaultValue() {
+ val objectJsonWithDefaults = Json(objectJson) {
+ encodeDefaults = true
+ }
+
+ val arrayJsonWithDefaults = Json(arrayJson) {
+ encodeDefaults = true
+ }
+
+ val defaultChild = Sealed.DefaultChild()
+ encodeAndDecode(Sealed.serializer(), defaultChild, arrayJson) {
+ assertEquals("default_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(null, dynamicValue.default, "arrayJson should not encode defaults")
+ assertEquals(defaultChild.intField, dynamicValue.intField)
+ assertEquals(1, fieldsCount(dynamicValue))
+ }
+ encodeAndDecode(Sealed.serializer(), defaultChild, arrayJsonWithDefaults) {
+ assertEquals("default_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(defaultChild.default, dynamicValue.default, "arrayJsonWithDefaults should encode defaults")
+ assertEquals(defaultChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+
+ encodeAndDecode(Sealed.serializer(), defaultChild, objectJson) {
+ assertEquals("default_child", this.type)
+ assertEquals(null, this.default, "objectJson should not encode defaults")
+ assertEquals(defaultChild.intField, this.intField)
+ assertEquals(2, fieldsCount(this))
+ }
+ encodeAndDecode(Sealed.serializer(), defaultChild, objectJsonWithDefaults) {
+ assertEquals("default_child", this.type)
+ assertEquals(defaultChild.default, this.default, "objectJsonWithDefaults should encode defaults")
+ assertEquals(defaultChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+
+ }
+
+ @Test
+ fun testNonDefaultValue() {
+ val nonDefaultChild = Sealed.DefaultChild("non default value")
+ encodeAndDecode(Sealed.serializer(), nonDefaultChild, arrayJson) {
+ assertEquals("default_child", this[0])
+ val dynamicValue = this[1]
+ assertEquals(nonDefaultChild.default, dynamicValue.default)
+ assertEquals(nonDefaultChild.intField, dynamicValue.intField)
+ assertEquals(2, fieldsCount(dynamicValue))
+ }
+
+ encodeAndDecode(Sealed.serializer(), nonDefaultChild, objectJson) {
+ assertEquals("default_child", this.type)
+ assertEquals(nonDefaultChild.default, this.default)
+ assertEquals(nonDefaultChild.intField, this.intField)
+ assertEquals(3, fieldsCount(this))
+ }
+ }
+
  @Test
  fun testObject() {
  val value = Sealed.ObjectChild