Issued around tput

[gregoa]

Besides the problem with the shell redirection, which I already reported at https://rt.cpan.org/Public/Bug/Display.html?id=130463, there are more problems with the use of tput.

As https://bugs.debian.org/939939 and the linked log at https://ci.debian.net/data/autopkgtest/testing/amd64/libt/libterm-choose-perl/2922560/log.gz show, tput fails if TERM is not set. Interestingly there is a difference between tput -V and other tput calls:

% env -u TERM tput -V ; echo $?                          
ncurses 6.1.20181013                            
0
% env -u TERM tput ; echo $?
tput: No value for $TERM and no -T specified
2
% env -u TERM tput rev ; echo $?
tput: No value for $TERM and no -T specified
2

This means that the failures don't come from the tpuz -V in the if() but from the actual calls later in the code.

When looking at the code in lib/Term/Choose/Screen.pm I was a bit confused; is the logic of the if()in line 37 really how it's meant to be? If I'm reading this correctly, what's happening is (in pseudo-code):

if (we are on windows or TC_ANSI_ESCAPES is set or we have a working tput) {
    use ansi escapes
} else {
    use tput
}

Shouldn't this be or we don't have a working tput? -- Maybe something like the following might work (untested):

--- a/lib/Term/Choose/Screen.pm
+++ b/lib/Term/Choose/Screen.pm
@@ -34,7 +34,7 @@ my (


 BEGIN {
-    if ( $^O eq 'MSWin32' || $ENV{TC_ANSI_ESCAPES} || system( "tput -V &> /dev/null" ) ) {
+    if ( $^O eq 'MSWin32' || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || ! system( "tput -V >/dev/null 2>&1" ) ) {
         @up    = ( "\e[", "A" );
         @down  = ( "\e[", "B" );
         @right = ( "\e[", "C" );

Cheers,
gregor, Debian Perl Group

[kuerbis]

Hi gregor, if I am not wrong system returns zero on successful execution.

Would id be OK to write it like this?

if ( $^O eq 'MSWin32' || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0 ) {

[gregoa]

Hi gregor, if I am not wrong system returns zero on successful execution.

Oh, right :/

Would id be OK to write it like this?
if ( $^O eq 'MSWin32' || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0 ) {

I think this should work. -- Let's try a few things:

% env TERM=foo perl -E 'if ( $^O eq "MSWin32" || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0 ) { say "use ansi escapes"; } else { say "use tput"; }'
use tput
% env -u TERM perl -E 'if ( $^O eq "MSWin32" || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0 ) { say "use ansi escapes"; } else { say "use tput"; }'
use ansi escapes
% env TERM=foo perl -E 'if ( $^O eq "MSWin32" || $ENV{TC_ANSI_ESCAPES} || ! $ENV{TERM} || system( "trallala -V >/dev/null 2>&1" ) != 0 ) { say "use ansi escapes"; } else { say "use tput"; }'                                                         
use ansi escapes

Yeah, looks good :)

Thanks,
gregor

[kuerbis]

If I use system( "tput cuu >/dev/null 2>&1" ) != 0 I could skip the ! $ENV{TERM}.
Would you recommend to use the ! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0 or to use system( "tput cuu >/dev/null 2>&1" ) != 0?

[gregoa]

On Tue, 10 Sep 2019 22:06:38 -0700, kuerbis wrote: If I use `system( "tput cuu >/dev/null 2>&1" ) != 0` I could skip the `! $ENV{TERM}`.

Right, should work as well.

Would you recommend to use the `! $ENV{TERM} || system( "tput -V >/dev/null 2>&1" ) != 0` or to use `system( "tput cuu >/dev/null 2>&1" ) != 0`?

To be honest, I have no real preference … Thinking a bit … Maybe the latter is indeed slightly better as it avoids a comment ("what is this $ENV{TERM} about?"), and I only proposed it because `tput -V' is a bit weird; so yeah, no objections from my side :) Cheers, gregor

…

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[kuerbis]

! qx(tput cuu 2>/dev/null) is a little shorter and looks a little simpler then system( "tput cuu >/dev/null 2>&1" ) != 0.
If there is something wrong with ! qx(tput cuu 2>/dev/null) please write a comment else I will use ! qx(tput cuu 2>/dev/null).

[gregoa]

On Wed, 11 Sep 2019 21:06:32 -0700, kuerbis wrote: `! qx(tput cuu 2>/dev/null)` is a little shorter and looks a little simpler then `system( "tput cuu >/dev/null 2>&1" ) != 0`. If there is something wrong with `! qx(tput cuu 2>/dev/null)` please write a comment else I will use `! qx(tput cuu 2>/dev/null)`.

Agreed, and seems to do the job as well.>

…

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[kuerbis]

Thx!

[gregoa]

On Thu, 12 Sep 2019 14:41:39 +0000, kuerbis wrote: Closed #6.

Thanks for the fix. I just uploaded 1.701 to Debian and I'm optimistic that all works out fine :) Thanks again, gregor

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