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

[Jeff King <peff@peff.net>]

On Wed, Apr 05, 2023 at 09:18:20PM -0500, Felipe Contreras wrote:

> On Wed, Apr 5, 2023 at 2:09 PM Jeff King <peff@peff.net> wrote:
> > On Wed, Apr 05, 2023 at 07:32:22PM +0200, Patrick Steinhardt wrote:
> 
> > IMHO we should aim for fixing those inconsistencies, and then letting
> > people set PERL_PATH as appropriate (even to something that will find it
> > via $PATH if they want to).
> 
> We can aim to fix all those inconsistencies *eventually* while in the
> meantime make them runnable for most people *today*.
> 
> It's not a dichotomy.

It is if the proposed patches change the behavior in such a way as to
make things less consistent.

There are three plausible perls to run (whether intentionally or
accidentally):

  1. the one in PERL_PATH

  2. /usr/bin/perl

  3. the first one in $PATH

What the code tries to do now is to consistently use (1). If there are
cases that accidentally use (2), which is what I took Patrick's patch to
mean, then that is a problem for people who set PERL_PATH to something
else, but not for people who leave it as /usr/bin/perl. If we "fix"
those cases by switching them to (3), then now things are less
consistent for such people than when we started.

But I am not clear on what those cases are (if any), and we have not
seen Patrick's follow-up proposed patch.

I did find one case that is accidentally doing (3), and posted a patch
elsewhere in the thread to convert it to (1). If you prefer behavior
(3), you might consider that a regression, but it seems meaningless
given the 99% of other cases that are using (1). If you want (3) to be
the behavior everywhere, then we'd need to completely change our stance
on how we invoke perl, or we need to teach PERL_PATH to handle this case
so that people building Git can choose their own preference (sadly I
don't think "make PERL_PATH='/usr/bin/env perl'" quite works because we
have to shell-quote it in some contexts before evaluating).

-Peff