Subject: Re: [PATCH v2 1/3] chainlint: sidestep impoverished macOS "terminfo"

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Fri, 11 Nov 2022 15:55:15 +0100

On Fri, Nov 11 2022, Eric Sunshine via GitGitGadget wrote:

> From: Eric Sunshine <[email-masked]>
>
> Although the macOS Terminal.app is "xterm"-compatible, its corresponding
> "terminfo" entries -- such as "xterm", "xterm-256color", and
> "xterm-new"[1] -- neglect to mention capabilities which Terminal.app
> actually supports (such as "dim text"). This oversight on Apple's part
> ends up penalizing users of "good citizen" console programs which
> consult "terminfo" to tailor their output based upon reported terminal
> capabilities (as opposed to programs which assume that the terminal
> supports ANSI codes). The same problem is present in other Apple
> "terminfo" entries, such as "nsterm"[2], with which macOS Terminal.app
> may be configured.
>
> Sidestep this Apple problem by imbuing get_colors() with specific
> knowledge of capabilities common to "xterm" and "nsterm", rather than
> trusting "terminfo" to report them correctly. Although hard-coding such
> knowledge is ugly, "xterm" support is nearly ubiquitous these days, and
> Git itself sets precedence by assuming support for ANSI color codes. For
> other terminal types, fall back to querying "terminfo" via `tput` as
> usual.
>
> FOOTNOTES
>
> [1] iTerm2 FAQ suggests "xterm-new": https://iterm2.com/faq.html
>
> [2] Neovim documentation recommends terminal type "nsterm" with
>     Terminal.app: https://neovim.io/doc/user/term.html#terminfo
>
> Signed-off-by: Eric Sunshine <[email-masked]>
> ---
>  t/chainlint.pl | 35 +++++++++++++++++++++++------------
>  1 file changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/t/chainlint.pl b/t/chainlint.pl
> index 7972c5bbe6f..0ee5cc36437 100755
> --- a/t/chainlint.pl
> +++ b/t/chainlint.pl
> @@ -653,21 +653,32 @@ my @NOCOLORS = (bold => '', rev => '', reset => '', blue => '', green => '', red
>  my %COLORS = ();
>  sub get_colors {
>  	return \%COLORS if %COLORS;
> -	if (exists($ENV{NO_COLOR}) ||
> -	    system("tput sgr0 >/dev/null 2>&1") != 0 ||
> -	    system("tput bold >/dev/null 2>&1") != 0 ||
> -	    system("tput rev  >/dev/null 2>&1") != 0 ||
> -	    system("tput setaf 1 >/dev/null 2>&1") != 0) {
> +	if (exists($ENV{NO_COLOR})) {
>  		%COLORS = @NOCOLORS;
>  		return \%COLORS;
>  	}
> -	%COLORS = (bold  => `tput bold`,
> -		   rev   => `tput rev`,
> -		   reset => `tput sgr0`,
> -		   blue  => `tput setaf 4`,
> -		   green => `tput setaf 2`,
> -		   red   => `tput setaf 1`);
> -	chomp(%COLORS);
> +	if ($ENV{TERM} =~ /xterm|xterm-\d+color|xterm-new|xterm-direct|nsterm|nsterm-\d+color|nsterm-direct/) {
> +		%COLORS = (bold  => "\e[1m",
> +			   rev   => "\e[7m",
> +			   reset => "\e[0m",
> +			   blue  => "\e[34m",
> +			   green => "\e[32m",
> +			   red   => "\e[31m");
> +		return \%COLORS;
> +	}
> +	if (system("tput sgr0 >/dev/null 2>&1") == 0 &&
> +	    system("tput bold >/dev/null 2>&1") == 0 &&
> +	    system("tput rev  >/dev/null 2>&1") == 0 &&
> +	    system("tput setaf 1 >/dev/null 2>&1") == 0) {
> +		%COLORS = (bold  => `tput bold`,
> +			   rev   => `tput rev`,
> +			   reset => `tput sgr0`,
> +			   blue  => `tput setaf 4`,
> +			   green => `tput setaf 2`,
> +			   red   => `tput setaf 1`);
> +		return \%COLORS;
> +	}
> +	%COLORS = @NOCOLORS;
>  	return \%COLORS;
>  }

Doesn't test-lib.sh have the same problem then?

This is somewhat of an aside, as we're hardcoding thees colors in
t/chainlint.pl now, but I wondered when that was added (but I don't
think I commented then) why it needed to be re-hardcoding the coloring
we've got in test-lib.sh.

I.e. if test-lib.sh is running it could we handle these cases, and just
export a variable with the color info for "bold" or whatever in
GIT_TEST_COLOR_BOLD, then pick that up?

I have a local semi-related patch which made much the same change to
test-lib.sh itself, to support --color without going through whether
tput thinks we support colors:
https://github.com/avar/git/commit/c4914db758b

I think this is fine for now if you don't want to poke more at it, but
maybe this should all be eventually combined?

I also wonder to what extent this needs to be re-inventing
Term::ANSIColor, which has shipped with Perl since 5.6, so we can use it
without worrying about version compat, but that's another topic...