Pickling an empty list does not produce an empty JSON array

[manuelbernhardt]

scala> import scala.pickling._, Defaults._
import scala.pickling._
import Defaults._

scala>  import json._
import json._

scala> case class Foo(list: List[String])
defined class Foo

scala> Foo(List.empty).pickle
<console>:19: warning: method newTermName in trait Names is deprecated: Use TermName instead
              Foo(List.empty).pickle
                              ^
res0: scala.pickling.json.pickleFormat.PickleType =
JSONPickle({
  "$type": "Foo",
  "list": {
    "$type": "scala.collection.immutable.Nil.type"
  }
})

I would expect list not to be an object but an empty JSON array instead

[manuelbernhardt]

Nevermind, I think I may have misunderstood the aim of the JSON pickler - am I right that the JSON pickler is just meant to turn a type into a string representation that happens to be JSON rather than a JSON format that is meant for manipulation as-is?

[havocp]

the JSON format that comes with pickling doesn't produce very "natural" JSON. the one that's in sbt serialization generates something that's probably more what you were expecting.

[jsuereth]

Yeah, I think maybe we need to contribute our JSON back, or just make a note that it exists.

We use json4s + jawn, which is not zero-dependency, hence it can't be part of the pickling library directly, but rather an external module.

[eed3si9n]

I think the readme or the talk said pickling's JSON implementation inlines the String operations on compile-time so the runtime performance is really good. sbt/serialization's implementation is less hardcore about runtime perf, but aims for natural, organic feelings of humans. (which is not a bad thing when you're using this for json API)
We should perhaps run some benchmark and tables. Also we should make the doc page. @heathermiller was saying we can use docs.scala-lang.org.

[manuelbernhardt]

I'd very much welcome an indication as to the nature of the JSON being produced, perhaps going as far as to renaming it to SyntheticJSON as I believe this is not what Crockford had in mind when he set out to create JSON.

To clarify: the use-case I'm having at the moment is to implement a CQRS system where the UI is in Javascript, all Commands and Events implementing the same traits. Therefore I was looking for a tool to allow de/serialization of the messages using a type hint of sorts. @yanns pointed me to https://github.com/sphereio/sphere-scala-libs/tree/master/json which I am going to give a shot now. Would sbt-serialization support this use-case as well?