Coproduct Encoder for Argonaut

coproductEncoder.scala

import shapeless.{Poly1, Coproduct}
import shapeless.ops.coproduct.Folder

import argonaut.{_}
import argonaut.Argonaut._

  /**
   * Generic encoder for Coproducts, will only resolve if all types in a Coproduct has an EncodeJson in scope
   */
  object CoproductToArgonautFolder extends Poly1 {
    implicit def caseAnyJsonable[A: EncodeJson] = at[A](_.asJson)
  }

  implicit def coproductEncode[A <: Coproduct, Out <: Json](implicit fldr: Folder.Aux[CoproductToArgonautFolder.type, A, Out]): EncodeJson[A] =
    EncodeJson(_.fold(CoproductToArgonautFolder))