Why can’t `io.ktor.client.features.json.JsonSerializer.read(..)` return the nullable `Any?` and why ...

# ktor

[Sam Garfinkel]

Why can’t io.ktor.client.features.json.JsonSerializer.read(..) return the nullable Any? and why can’t the write function accept Any?? Is this just how they were designed, or is there an actual implementation constraint?

[Shawn]

are you talking about, like, if the body is invalid?

[Sam Garfinkel]

You might want to map an empty body to null.

[Sam Garfinkel]

Likewise you might want to write null as an empty string or something.

[Sam Garfinkel]

The point is it doesn’t follow the semantics of kotlinx.serialization which supports serializers for nullables.

[Shawn]

as I understand it, kotlinx.serialization supports serialization for nullable fields, but I don’t see how that pertains to the JsonSerializer read/write methods

[Shawn]

if I’m not mistaken, the intent of those methods is to read and write a complete and valid JSON blob, and null or a string that reads "null" doesn’t fit the bill

[Sam Garfinkel]

Fair enough. The reason I even ask the question is because the prototype from kotlinx.serializaiton is Json.parse(KSerializer<T>, String): T, but because serializer(KType) returns a KSerializer<Any?> the built-in Json Serializer has to use the !! operator. I guess this is kinda an esoteric discussion.

[Sam Garfinkel]

Also to follow on what you said, the JsonSerializer does not support a suspend fun foo(): Bar? = client.get("<http://example.com>") ? Because read can’t return null.