How to correctly process !!binary on a given YAML?

[andrefrsousa]

Hello!

Imagine that you have this YAML file content:

body: !!binary |-
      /9j/4AAQSkZJRgABAQAASABIAAD/4QBYRXhpZgAATU0AKgAAAAgAAgESAAMAAAABAAEAAI

When parsing it and converting it again to string, the representation of the binary changes since the tag is removed in the process. How to enforce that information is keep between decodeFromString/encodeToString processes?

Here is the code I have right now:

@Serializable
data class Body(
    @Serializable(with = BodySerializer::class) val body: Any?,
)

object BodySerializer : KSerializer<Any?> {
    override val descriptor: SerialDescriptor = PrimitiveSerialDescriptor("Body", PrimitiveKind.STRING)

    override fun serialize(encoder: Encoder, value: Any?) {
        when (value) {
            is String -> encoder.encodeString(value) // Serialize String as is
            is ByteArray -> {
                // Serialize ByteArray with !!binary tag
                encoder.encodeString("!!binary |- ${Base64.getEncoder().encodeToString(value)}")
            }
            else -> encoder.encodeString(value?.toString() ?: "") // Handle other types or null values
        }
    }

    override fun deserialize(decoder: Decoder): Any? {
        val decodedString = decoder.decodeString()

        return try {
            Base64.getDecoder().decode(decodedString)
        } catch (e: IllegalArgumentException) {
            decodedString
        }
    }
}

The output I receive is:

body: '!!binary |- /9j/4AAQSkZJRgABAQAASABIAAD/4QBYRXhpZgAATU0AKgAAAAgAAgESAAMAAAABAAEAAA=='

Yaml configuration:

val yaml = Yaml(
    configuration = YamlConfiguration(
        encodeDefaults = false,
        strictMode = false,
        polymorphismStyle = PolymorphismStyle.Tag,
        codePointLimit = Integer.MAX_VALUE,
        breakScalarsAt = 256,
        singleLineStringStyle = SingleLineStringStyle.Plain,
        multiLineStringStyle = MultiLineStringStyle.Plain,
        allowAnchorsAndAliases = true,
    )
)

[charleskorn]

This isn't something currently supported by Kaml.

Emitting the tag with encodeString won't work as the underlying YAML library will escape the value to ensure it is preserved as a string rather than treated a tag.

If you'd like to raise a PR to add support for this scenario, I'd be happy to review it.