pattern matching on terraform json variations

tf_file_type.ml

(* val type_ : Yojson.Safe.t -> [ `Plan | `State | `Unknown ] *)

let type_ json =
  let module Plan = struct
    type t = {
      terraform_version : string;
      planned_values : Yojson.Safe.t;
    }
    [@@deriving of_yojson { strict = false }]
  end in
  let module State = struct
    type t = {
      terraform_version : string;
      root_module : Yojson.Safe.t;
    }
    [@@deriving of_yojson { strict = false }]
  end in
  match (Plan.of_yojson json, State.of_yojson json) with
  | Ok _, Ok _ -> `Unknown
  | Ok _, _ -> `Plan
  | _, Ok _ -> `State
  | _ -> `Unknown