fix: status line enabled when ANSI colors are forced (#6503) (#6556)

We want to enable the status line if and only if stderr is a tty. ANSI
color usage was tweaked in 3.6.0 with #6340 to allow users to force
colors. As status line activation actually depended on whether ANSI
colors were enabled or not, this change had the side effect to always
enable the status line even when ANSI colors were requested for
something that's not a tty.

Fix this by exposing a simple lazy wrapper of Unix.isatty to use
instead of Ansi_color.stderr_supports_color.

Signed-off-by: Antonin Décimo <antonin@tarides.com>

Signed-off-by: Antonin Décimo <antonin@tarides.com>
Co-authored-by: Antonin Décimo <antonin@tarides.com>

CHANGES.md

@@ -1,3 +1,8 @@
+3.6.1 (unreleased)
+------------------
+
+- Fix status line enabled when ANSI colors are forced. (#6503, @MisterDA)
+
 3.6.0 (2022-11-14)
 ------------------
 

bin/common.ml

@@ -162,7 +162,7 @@ let init ?log_file c =
   in
   let config =
     Dune_config.adapt_display config
-      ~output_is_a_tty:(Lazy.force Ansi_color.stderr_supports_color)
+      ~output_is_a_tty:(Lazy.force Ansi_color.output_is_a_tty)
   in
   Dune_config.init config;
   Dune_util.Log.init () ?file:log_file;

otherlibs/stdune/ansi_color.ml

@@ -146,6 +146,8 @@ let stdout_supports_color = lazy (supports_color Unix.stdout)
 
 let stderr_supports_color = lazy (supports_color Unix.stderr)
 
+let output_is_a_tty = lazy (Unix.isatty Unix.stderr)
+
 let rec tag_handler current_styles ppf styles pp =
   Format.pp_print_as ppf 0 (Style.escape_sequence_no_reset styles);
   Pp.to_fmt_with_tags ppf pp

otherlibs/stdune/ansi_color.mli

@@ -95,6 +95,8 @@ val stdout_supports_color : bool Lazy.t
 
 val stderr_supports_color : bool Lazy.t
 
+val output_is_a_tty : bool Lazy.t
+
 (** Filter out escape sequences in a string *)
 val strip : string -> string