Re: [PATCH] global: resolve Perl executable via PATH

[Jeff King <peff@peff.net>]

On Wed, Apr 05, 2023 at 12:10:10PM +0200, Patrick Steinhardt wrote:

> The majority of Perl scripts we carry in Git have a `#!/usr/bin/perl`
> shebang. This is not a portable location for the Perl interpreter and
> may thus break on some systems that have the interpreter installed in a
> different location. One such example is NixOS, where the only executable
> installed in `/usr/bin` is env(1).
> 
> Convert the shebangs to resolve the location of the Perl interpreter via
> env(1) to make these scripts more portable. While the location of env(1)
> is not guaranteed by any standard either, in practice all distributions
> including NixOS have it available at `/usr/bin/env`. We're also already
> using this idiom in a small set of other scripts, and until now nobody
> complained about them.
> 
> This makes the test suite pass on NixOS.

Can you tell us more about which tests failed?

Skimming over the list of files here, the first few examples:

>  Documentation/build-docdep.perl                    | 2 +-
>  Documentation/cat-texi.perl                        | 2 +-
>  Documentation/cmd-list.perl                        | 3 ++-
>  Documentation/fix-texi.perl                        | 4 +++-
>  Documentation/lint-fsck-msgids.perl                | 2 +-

will not be affected by your patch, because we never use their shebang
lines at all (we say "$PERL_PATH cmd-list.perl" in the Makefile).

I did try removing /usr/bin/perl completely (and thus likewise had no
perl in my path), setting PERL_PATH, and got a few broken tests, which
could be fixed as below.

Does this fix the cases you saw, or are there others?

-- >8 --
Subject: [PATCH] t/lib-httpd: pass PERL_PATH to CGI scripts

As discussed in t/README, tests should aim to use PERL_PATH rather than
straight "perl". We usually do this automatically with a "perl" function
in test-lib.sh, but a few cases need to be handled specially.

One such case is the apply-one-time-perl.sh CGI, which invokes plain
"perl". It should be using $PERL_PATH, but to make that work, we must
also instruct Apache to pass through the variable.

Prior to this patch, doing:

  mv /usr/bin/perl /usr/bin/my-perl
  make PERL_PATH=/usr/bin/my-perl test

would fail t5702, t5703, and t5616. After this it passes. This is a
pretty extreme case, as even if you install perl elsewhere, you'd likely
still have it in your $PATH. A more realistic case is that you don't
want to use the perl in your $PATH (because it's older, broken, etc) and
expect PERL_PATH to consistently override that (since that's what it's
documented to do). Removing it completely is just a convenient way of
completely breaking it for testing purposes.

Signed-off-by: Jeff King <peff@peff.net>
---
 t/lib-httpd/apache.conf            | 2 ++
 t/lib-httpd/apply-one-time-perl.sh | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/t/lib-httpd/apache.conf b/t/lib-httpd/apache.conf
index f43a25c1f10..9e6892970de 100644
--- a/t/lib-httpd/apache.conf
+++ b/t/lib-httpd/apache.conf
@@ -101,6 +101,8 @@ PassEnv LC_ALL
 Alias /dumb/ www/
 Alias /auth/dumb/ www/auth/dumb/
 
+SetEnv PERL_PATH ${PERL_PATH}
+
 <LocationMatch /smart/>
 	SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
 	SetEnv GIT_HTTP_EXPORT_ALL
diff --git a/t/lib-httpd/apply-one-time-perl.sh b/t/lib-httpd/apply-one-time-perl.sh
index 09a0abdff7c..d7f9fed6aee 100644
--- a/t/lib-httpd/apply-one-time-perl.sh
+++ b/t/lib-httpd/apply-one-time-perl.sh
@@ -13,7 +13,7 @@ then
 	export LC_ALL
 
 	"$GIT_EXEC_PATH/git-http-backend" >out
-	perl -pe "$(cat one-time-perl)" out >out_modified
+	"$PERL_PATH" -pe "$(cat one-time-perl)" out >out_modified
 
 	if cmp -s out out_modified
 	then
-- 
2.40.0.824.g7b678b1f643