Use Fmt.error_msg in more places (#44)

Author: MisterDA

worker/process.ml

@@ -5,8 +5,8 @@ type error = [ `Cancelled | `Exit_code of int | `Msg of string ]
 let send_to ch contents =
   Lwt.try_bind
     (fun () -> Lwt_io.write ch contents >>= fun () -> Lwt_io.close ch)
-    (fun () -> Lwt.return (Ok ()))
-    (fun ex -> Lwt.return (Error (`Msg (Printexc.to_string ex))))
+    (fun () -> Lwt_result.return ())
+    (fun ex -> Lwt.return (Fmt.error_msg "%a" Fmt.exn ex))
 
 let pp_signal f x =
   let open Sys in
@@ -34,19 +34,17 @@ let exec ~label ~log ~switch ?env ?(stdin = "") ?(stderr = `FD_copy Unix.stdout)
   | _ when not (Lwt_switch.is_on switch) -> Error `Cancelled
   | Unix.WEXITED n when is_success n -> (
       match stdin_result with
-      | Ok () -> Ok ()
+      | Ok _ as ok -> ok
       | Error (`Msg msg) ->
-          Error (`Msg (Fmt.str "Failed sending input to %s: %s" label msg)))
+          Fmt.error_msg "Failed sending input to %s: %s" label msg)
   | Unix.WEXITED n -> Error (`Exit_code n)
-  | Unix.WSIGNALED x ->
-      Error (`Msg (Fmt.str "%s failed with signal %d" label x))
+  | Unix.WSIGNALED x -> Fmt.error_msg "%s failed with signal %d" label x
   | Unix.WSTOPPED x ->
-      Error (`Msg (Fmt.str "%s stopped with signal %a" label pp_signal x))
+      Fmt.error_msg "%s stopped with signal %a" label pp_signal x
 
 let check_call ~label ~log ~switch ?env ?stdin ?stderr ?is_success cmd =
   exec ~label ~log ~switch ?env ?stdin ?stderr ?is_success cmd >|= function
   | Ok () -> Ok ()
   | Error `Cancelled -> Error `Cancelled
-  | Error (`Exit_code n) ->
-      Error (`Msg (Fmt.str "%s failed with exit-code %d" label n))
+  | Error (`Exit_code n) -> Fmt.error_msg "%s failed with exit-code %d" label n
   | Error (`Msg _) as e -> e