Uninterpreted extension 'to_yojson'.

[anentropic]

I'm trying to work out how to define my own to/from functions for some types that can't be derived automatically

I'm getting this error:

57 |     |> [%to_yojson: (string * Version.t) list]
              ^^^^^^^^^
Error: Uninterpreted extension 'to_yojson'.

I have (preprocess (pps ppx_yojson_conv)) and (libraries yojson) in my dune file

Is something else needed?

Also the readme seems to suggest that Hashtbl can be derived https://github.com/janestreet/ppx_yojson_conv#hash-tables

but:

module X = struct
  type t = (string, string) Hashtbl.t [@@deriving yojson]
end

gives: Unbound value Hashtbl.t_of_yojson

[anentropic]

the former seems to need (libraries ppx_deriving_yojson.runtime)?

[smorimoto]

Is there any update on this? I don't have enough time to take a deep look, but I stuck.

[hhugo]

It's not to_yojson. It should be [%yojson_of: ...]

[anentropic]

🤦‍♂️ thanks