serialize option None field on a object as json null

[wenhoujx]

hello i found closed ticket #70 which concludes with "None fields on an object is dropped", however my use case actually asks for those null to be present.

For example, the following test fails.

I wonder if there is a way to configure the null encoding behavior. 🙏

  case class Foo(bar: Option[Bar])
  case class Bar(baz: Option[String])

    test("test encoding null") {
      assertTrue(Foo(Some(Bar(baz=None))).toJson == """{"bar":{"baz":null}}""")
    }

btw, i also found #638, which has a OptionAsJsonNull wrapper. But i don't control all of the classes to be JSON serialized, so i don't think this wrapper helps me.

[Andrapyre]

@wenhoujx , could you explain the use case further? Usage of null in Scala code is generally considered an anti-pattern.

[wenhoujx]

@Andrapyre hi, i am not trying to use null in scala, i am trying to use json null .

encoding: Option None -> json null
decoding: json null -> Option None.

it's a good idea to not encoding json null fields in a json object, however it's nice to be able to control that behavior.

[wenhoujx]

we figured out we can use implicit codec, however this doesn't work for zio-json 0.2.0-M4, works on zio-json 0.6.2.

0.2.0-M4 is the last version for zio 1 ? is that LTS? if so i think there is a bug.

object JsonNull {
  import zio.json._  
  import zio.json.ast._
  import zio.json.internal._
  
  implicit def explicitlyNullOption[A](implicit A: JsonEncoder[A]): JsonEncoder[Option[A]] = new JsonEncoder[Option[A]] {

    def unsafeEncode(oa: Option[A], indent: Option[Int], out: Write): Unit = oa match {
      case None    => out.write("null")
      case Some(a) => A.unsafeEncode(a, indent, out)
    }

    // This is the only override we need to produce the behavior, but 
    // unfortunately I did't see a clean way to pull the default
    // JsonEncoder[Option[A]] and override only this.  YMMV
    override def isNothing(oa: Option[A]): Boolean = false

    override final def toJsonAST(oa: Option[A]): Either[String, Json] =
      oa match {
        case None    => Right(Json.Null)
        case Some(a) => A.toJsonAST(a)
      }
  }
}  

object Codecs  {
  import JsonNull.explicitlyNullOption // import this at implicit macro expansion. 
  lazy implicit val codecBar = DeriveJsonCodec.gen[Bar]
  lazy implicit val codecFoo = DeriveJsonCodec.gen[Foo]
}

[jdegoes]

/bounty $100 for making it configurable in some nice and consistent way.

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Attempt	Started (GMT+0)	Solution
🟢 @987Nabil		#1100

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