Hiding the status line means also to forget it

Otherwise hiding then printing user message would show back the old status line

src/scheduler.ml

@@ -534,7 +534,7 @@ let update_status_line () =
   let gen_status_line = !status_line_generator () in
   match gen_status_line with
   | { message = None; _ } ->
-    Console.hide_status_line ();
+    Console.clear_status_line ();
   | { message = Some status_line; show_jobs } ->
     let status_line =
       if show_jobs then
@@ -667,7 +667,7 @@ end = struct
     let* () = Fiber.yield () in
     let count = Event.pending_jobs () in
     if count = 0 then begin
-      Console.hide_status_line ();
+      Console.clear_status_line ();
       Fiber.return Done
     end else begin
       update_status_line ();

src/stdune/console.ml

@@ -25,8 +25,9 @@ module T = struct
     if t.status_line_len > 0 then
       Printf.eprintf "\r%*s\r" t.status_line_len ""
 
-  let show_status_line s =
-    Ansi_color.prerr s
+  let show_status_line t =
+    if t.status_line_len > 0 then
+      Ansi_color.prerr t.status_line
 
   let update_status_line t status_line =
     if t.display = Progress then begin
@@ -37,27 +38,29 @@ module T = struct
         String.length (Format.asprintf "%a" Pp.render_ignore_tags status_line)
       in
       hide_status_line t;
-      show_status_line status_line;
-      flush stderr;
       t.status_line <- status_line;
-      t.status_line_len <- status_line_len
+      t.status_line_len <- status_line_len;
+      show_status_line t;
+      flush stderr;
     end
 
   let print t msg =
     hide_status_line t;
     prerr_string msg;
-    show_status_line t.status_line;
+    show_status_line t;
     flush stderr
 
   let print_user_message t ?config msg =
     hide_status_line t;
     Option.iter msg.User_message.loc ~f:(Loc.print Format.err_formatter);
     User_message.prerr ?config { msg with loc = None };
-    show_status_line t.status_line;
+    show_status_line t;
     flush stderr
 
-  let hide_status_line t =
+  let clear_status_line t =
     hide_status_line t;
+    t.status_line <- Pp.nop;
+    t.status_line_len <- 0;
     flush stderr
 
 end
@@ -77,7 +80,7 @@ let t () =
 let display () = (t ()).display
 
 let update_status_line status_line = T.update_status_line (t ()) status_line
-let hide_status_line () = T.hide_status_line (t ())
+let clear_status_line () = T.clear_status_line (t ())
 let print msg =
   match !t_var with
   | None -> Printf.eprintf "%s%!" msg

src/stdune/console.mli

@@ -1,3 +1,6 @@
+(** Manage printing user message and keeping progress information in the status line *)
+
+
 module Display : sig
 
     type t =
@@ -23,9 +26,9 @@ val init : Display.t -> unit
 (** Everything below this line requires [init] to have been called earlier. *)
 
 val update_status_line : User_message.Style.t Pp.t -> unit
-(** Update the status line if the display is in progress mode *)
+(** Update the status line if the display is in progress mode. *)
 
-val hide_status_line : unit -> unit
-(** Hide the status line *)
+val clear_status_line : unit -> unit
+(** Clear the status line *)
 
 val display : unit -> Display.t