Play JSON format syntax for HLists

playshapeless.scala

  import shapeless.::

  object Extensions extends LowPriorityExtensions {

    implicit class NotHListOWritesConcat[A](right: OWrites[A])(implicit notHList: shapeless.Refute[A <:< HList]) {
      //noinspection ScalaStyle
      def ~::[B](head: OWrites[B]): OWrites[B :: A :: HNil] = (head ~ right) (hlist => (hlist.head, hlist.tail.head))
    }

    implicit class NotHListReadsConcat[A](right: Reads[A])(implicit notHList: shapeless.Refute[A <:< HList]) {
      //noinspection ScalaStyle
      def ~::[B](head: Reads[B]): Reads[B :: A :: HNil] = (head ~ right) ((b, a) => b :: a :: HNil)
    }

  }

  trait LowPriorityExtensions {

    implicit class HListOWritesConcat[A <: HList](right: OWrites[A]) {
      //noinspection ScalaStyle
      def ~::[B](head: OWrites[B]): OWrites[B :: A] = (head ~ right) (hlist => (hlist.head, hlist.tail))
    }

    implicit class HListReadsConcat[A <: HList](right: Reads[A]) {
      //noinspection ScalaStyle
      def ~::[B](head: Reads[B]): Reads[B :: A] = (head ~ right) ((b, a) => b :: a)
    }

  }

  import Extensions._