JsonConfiguration#ignoreUnknownKeys is not working.

[DSeeLP]

Describe the bug
Decoder#decodeSerializableValue ignores JsonConfiguration#ignoreUnknownKeys and an JsonDecodingException is thrown.

To Reproduce
https://gist.github.com/DSeeLP/c5055f616ad0b7e4337cdadd24d1c4e5

Expected behavior
It should deserialize it to FineRestResponse(value=kotlin.Unit) and discard the unknown keys.

Environment

• Kotlin version: 1.5.31
• Library version: 1.3.0
• Kotlin platforms: JVM
• Gradle version: 7.1.1
• JRE Version: OpenJDK 11.0.11
• OS: Fedora 34

[josepanguera]

In your example you're using Unit which is not serializable.

If you add this class

@Serializable
class Discard  // this could be named however you want

and then change the line

println(json.decodeFromString<RestResult<Unit>>(inputText))

for

println(json.decodeFromString<RestResult<Discard>>(inputText))

you'll see that it works as intended and and is in fact respecting the ignoreUnknownKeys setting.