com.rojoma.json.v3.util.OrJNull.scala Maven / Gradle / Ivy

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package com.rojoma.json.v3.util

import com.rojoma.json.v3.ast.JNull
import com.rojoma.json.v3.codec.JsonEncode

/** A helper class primary for use with the interpolator.  Import
  * `OrJNull.implicits._` to get an `orJNull` method on `Option[T]`
  * which encodes the value using `T`'s `JsonEncode` when it's `Some`
  * and as `JNull` when it's `None`.
  *
  * {{{
  * val x = Some(AnEncodableThing(...))
  * val y = Option.empty[AnEncodableThing]
  * json""" {
  *   x1 : \${x.orJNull},  // These two lines
  *   x2 : ?\$x,           // encode the same way.
  *   y1 : \${y.orJNull},  // This one produces `null`.
  *   y2 : ?\$y            // And this one is elided.
  * } """
  * }}}
  */
sealed abstract class OrJNull[+T]
object OrJNull {
  case class Some[+T](value: T) extends OrJNull[T]
  case object None extends OrJNull[Nothing]

  implicit def encode[T : JsonEncode]: JsonEncode[OrJNull[T]] =
    new JsonEncode[OrJNull[T]] {
      def encode(x: OrJNull[T]) =
        x match {
          case Some(v) => JsonEncode.toJValue(v)
          case None => JNull
        }
    }

  object implicits {
    implicit class OrJNullExt[T](val `private once 2.10 is no more`: Option[T]) extends AnyVal {
      def orJNull: OrJNull[T] =
        `private once 2.10 is no more` match {
          case scala.Some(x) => OrJNull.Some(x)
          case scala.None => OrJNull.None
        }
    }
  }
}