Encoder should remove None: Option[T] values

It would be nice if the Encoder would remove the key/value completely when the type is Option[T] and the value is None. Currently, it encodes None to JSON null.

(Json4s works this way.)

This code:

  case class Test(foo: String, bar: Option[String])
  implicit val testEncoder: Encoder[Test] = deriveEncoder
  println(Test("FOO", None).asJson.noSpaces)

currently prints:

{"foo":"FOO","bar":null}

I would like it to be:

{"foo":"FOO"}

[naderghanbari]

I agree that Printer should not touch the JSON by default. I also agree that Printer should have the power to make the result nicer if you want to. This could help in cases where the actual value is null (e.g. Java interop). So I think Printer is just fine as is.

I think the encoder, though, should drop None values by default and not encode them as null. It should, however, encode genuine null values as null and not drop them.

Similar to dropNullKeys = false in Printer, I think the encoder configuration can have something like dropNone = true.

[ckozak]

What was the reason to make dropNullKeys = false by default? It seems that not putting nulls is more common among other libraries.