Hey all, I have a serializer class for integer bac...

# serialization

[robgray]

Hey all, I have a serializer class for integer backed enums. I'd like to handle de-serializing a case that doesn't exist (ex. 3) by returning null instead of throwing an exception. Is this possible?

@kotlinx.serialization.Serializable(TestEnum.TestEnumSerializer::class)
    enum class TestEnum(val value: Int) {
        RED(0),
        GREEN(1),
        BLUE(2);

        @Serializer(forClass = TestEnum::class)
        companion object TestEnumSerializer : KSerializer<TestEnum> {
            private val map = values().associateBy(TestEnum::value)

            override val descriptor: SerialDescriptor
                get() = StringDescriptor

            override fun deserialize(decoder: Decoder): TestEnum {
                return map.getValue(decoder.decodeInt())
            }

            override fun serialize(encoder: Encoder, obj: TestEnum) {
                encoder.encodeInt(obj.value)
            }
        }
    }

[Nikky]

first of all you need to use TestEnum? and then you can use map.get(decoder.decodeInt()) ?: null i think

[robgray]

When I change it to optional i get this build error Can't serialize non-nullable field of type TestEnum with nullable serializer TestEnumSerializer

[turansky]

KSerializer<TestEnum> -> KSerializer<TestEnum?>

[robgray]

@kotlinx.serialization.Serializable(TestEnum.TestEnumSerializer::class)
    enum class TestEnum(val value: Int) {
        RED(0),
        GREEN(1),
        BLUE(2);

        @Serializer(forClass = TestEnum::class)
        companion object TestEnumSerializer : KSerializer<TestEnum?> {
            private val map = values().associateBy(TestEnum::value)

            override val descriptor: SerialDescriptor
                get() = StringDescriptor

            override fun deserialize(decoder: Decoder): TestEnum? {
                return map[decoder.decodeInt()]
            }

            override fun serialize(encoder: Encoder, obj: TestEnum?) {
                obj?.value?.let { encoder.encodeInt(it) }
            }
        }
    }

[robgray]

Codegen fails with an IllegalStateException - Cause: Can't serialize non-nullable field of type TestEnum with nullable serializer TestEnumSerializer

[robgray]

Upgrading to kotlin ‘1.35.0’ fixed this, thanks everyone!