AnyVal round-trip not working as expected

[anoto-moniz]

Hello!
We're working on migrating from json4s to jsoniter-scala, and hitting an issue with inlining. We have a similar setup to #1078 , but instead of a nested object, it's a Map[String, CustomType].

Here's a simplified view of the structure.

trait TopProperty extends Any
trait Property extends Any with TopProperty
case class DoubleProperty(value: Double) extends AnyVal with Property
case class StringProperty(value: String) extends AnyVal with Property

case class Container(
  name: String,
  properties: Map[String, Property],
  other: OtherCustomType
)

The JSON we need to support is

{"name": "foo", "properties": {"a": 4.0, "b": "bar"}, "other": {...}}

The encoding/serialization works as desired, producing the above JSON. But when I try to deserialize it using readFromString[Container], I get expected '{' at the position of the first value (4.0 in the example above). I've been unable to figure out why this asymmetry is occurring.

I've tried a bunch of other approaches, but the only one I've had success with is directly using the JsonWriter and JsonReader objects in a custom codec, which of course isn't ideal. Especially since the real class has about a dozen fields, a handful of which are complex classes.

[plokhotnyuk]

@anoto-moniz Thanks for reporting!

If generated codec cannot parse own output then it is a bug definitely.

As a workaround for your case if there are no more other implementation of Property the following custom codec could be used:

implicit val customCodecOfProperty: JsonValueCodec[Property] =
  new JsonValueCodec[Property] {
    def nullValue: Property = null

    def decodeValue(in: JsonReader, default: Property): Property = {
      val t = in.nextToken()
      in.rollbackToken()
      if (t == '"') StringProperty(in.readString(null))
      else DoubleProperty(in.readDouble())
    }

    def encodeValue(x: Property, out: JsonWriter): Unit = x match {
      case DoubleProperty(d) => out.writeVal(d)
      case StringProperty(s) => out.writeVal(s)
    }
  }

Is it an acceptable solution for you?

BTW, I was able to reproduce this bug only after adding sealed for the definition of Property trait to be a kind of a sum type. Unfortunately, jsoniter-scala-macros doesn't support sum types without discriminators, so the bug fix will be just throwing of a compilation error that AnyVal and one value classes with CodecMakerConfig.withInlineOneValueClasses(true) cannot be used as leaf sub-types for a base sum type.

[plokhotnyuk]

@anoto-moniz Please peek the latest release where codecs will not be generated for sum types with leaf classes that are AnyVal or one value classes with CodecMakerConfig.withInlineOneValueClasses(true).

[anoto-moniz]

@plokhotnyuk Thanks so much for the quick response! I updated my code with your suggested codec, and it works like a charm.

And I don't think the limitation you reference should cause my other use cases any problems. This use of sum types without type discriminators is unique in our codebase.