Flattening of option values

[xclerc]

I am unsure how important this is in practice, but the encoding of
option values makes Some (Some (... None)) equal to None.
Could this be an issue [when using types whose definitions are unknown]?

module M : sig
  type t[@@deriving show, yojson]
  val x : t
  val y : t
end = struct
  type t = int option [@@deriving show, yojson]
  let x = None
  let y = Some 1
end

type t = {
  n : string;
  v : M.t option;
}[@@deriving show, yojson]

let x = { n = "x"; v = Some M.x; }

let y = { n = "y"; v = Some M.y; }

let roundtrip v =
  match of_yojson (to_yojson v) with
  | Ok v' ->
    if v = v' then
      Printf.printf "equal\n%!"
    else
      Printf.printf "%S vs %S\n%!" (show v) (show v')
  | Error _ -> assert false

let () =
  roundtrip x;
  roundtrip y

[emillon]

That's the case with any type whose serialization can include null. For example [%of_yojson: unit option] serializes both Some () and None as null. I don't think it's a problem (and it's not really fixable), but that's probably worth mentioning in the "semantics" paragraph.

[xclerc]

Thanks for the feedback!