Kotlinx.serialization: 'ignoreUnknownKeys' configuration option does not work for Enums

[PhilipSA]

Describe the bug
If you have an EnumClass and the json contains an element not present in the enum it will crash:
kotlinx.serialization.SerializationException: com.example.testingstuff.Numbers does not contain element with name 'Two'

But since i have declared ignoreUnknownKeys = true i expect it to be either null or default to something.

I did not find anything about this in the documentation.

Also is there any workaround for this?

To Reproduce

enum class Numbers {
    One
}

@Serializable
data class EnumClass(
    val enumType: Numbers? = null
)

class ExampleUnitTest {
    @Test
    fun ignoreUnknownEnum() {
        val json = Json {
            ignoreUnknownKeys = true
        }
        //This will work
        var jsonString = "{\"enumType\": \"One\" }"
        json.decodeFromString(EnumClass.serializer(), jsonString)

        //This will crash
        jsonString = "{\"enumType\": \"Two\" }"
        json.decodeFromString(EnumClass.serializer(), jsonString)
    }
}

Expected behavior
enumType becomes null or Numbers.One

Environment

• Kotlin version: 1.4.10
• Library version: 1.0.0-RC2
• Kotlin platforms: Android JVM
• Gradle version: 4.0.1

[qwwdfsad]

It works as expected, ignoreUnknownKeys is designed to ignore unknown _keys_, not values.
But you can use coerceInputValues = true for the very purpose you described

[PhilipSA]

It works as expected, ignoreUnknownKeys is designed to ignore unknown _keys_, not values.
But you can use coerceInputValues = true for the very purpose you described

Nice that worked for the example case. But what about if it is a list of enums?

It still crashes when i change my example to this:

enum class Numbers {
    One
}

@Serializable
data class EnumClass(
    val enumType: List<Numbers?>
)

class ExampleUnitTest {
    @Test
    fun ignoreUnknownEnum() {
        val json = Json {
            ignoreUnknownKeys = true
            coerceInputValues = true
        }

        var jsonString = "{\"enumType\": [\"One\"] }"
        json.decodeFromString(EnumClass.serializer(), jsonString)

        jsonString = "{\"enumType\": [\"Two\"] }"
        json.decodeFromString(EnumClass.serializer(), jsonString)
    }
}

[qwwdfsad]

Currently, the only workaround is to write your own serializer.
We may consider implementing this functionality as part of coerceInputValues

[PhilipSA]

Currently, the only workaround is to write your own serializer.
We may consider implementing this functionality as part of coerceInputValues

Yes please. Consider this a feature request