Custom en/decoding attributes

[cemerick]

Deriving's show plugin allows one to use @printer to specify custom printers, e.g. from that README:

type file = {
  name : string;
  perm : int     [@printer fun fmt -> fprintf fmt "0o%03o"];
} [@@deriving show];;

It seems like an analogous ability here would be very useful. e.g. there are other tagged enhancements (e.g. #10, #87) for which @to_yojson/@of_yojson attributes would be reasonable workarounds / solutions.

Does this sound reasonable?

[whitequark]

Yeah, [@to_yojson]/[@from_yojson] seem fine.