bug#53355: bug#51466: bug#53355: guix shell --check: confusing error message

[bokr@bokr.com]

Hi Chris,

Did you observe this behaviour inside a git repo directory?
I wonder if this git security thing could be relevant:
    https://lwn.net/Articles/892755/
It makes also me wonder about readline completion stuff
possibly interacting. Isn't that implemented with readline?

I have had some mystery bash parsing errors, and I noticed
    set|less
shows a heck of a lot of functions defined that I don't
remember seeing in the past. 
Anyway, shouldn't stuff like that have better hygiene than just prefixed
_underscore ? Or maybe set|less doesn't show all that on your system?

Disclaimer: I played a lot of games trying to make stuff conditional
at login, where I  renamed .bash_profile and .bashrc (e.g. .my_bashrc)
which brought .profile into play, and I messed with the downstream
of that to source some .my_'s conditionally, so I've go a fragile mess right now ;/

Anyway, did you determine why things changed in the first place?
Or will this be a whack-a-mole game with future weirdnesses? :)

Semms like IWBN to have interfaces governed by contracts :)

Best,
Bengt Richter

On +2022-06-19 13:40:50 -0700, Chris Marusich wrote:
> Hi Ludo,
> 
> Thank you for the review!
> 
> Ludovic Courtès <ludo@gnu.org> writes:
> 
> > LGTM, please push!
> 
> Before pushing, I did some more tests to make sure it was still working.
> When I did this, I noticed that read-line was no longer returning
> strings that end in "\r".  This prevents child-shell-environment from
> behaving correctly, since it incorrectly assumes that all the lines end
> in "\r", stripping it off unconditionally.  In the past, I'm sure
> read-line was returning strings that end in "\r".  I don't know what
> changed, but I've attached a second patch that fixes this issue, also.
> 
> Unless you have more feedback, I'll go ahead and push both patches to
> master in a few days.
> 
> -- 
> Chris
> 
> PGP: https://savannah.gnu.org/people/viewgpg.php?user_id=106836

> From c4fee9e63f8cb694de86ae46bd1e2e4c692eb6f6 Mon Sep 17 00:00:00 2001
> From: Chris Marusich <cmmarusich@gmail.com>
> Date: Sun, 19 Jun 2022 13:16:04 -0700
> Subject: [PATCH] environment: Don't assume that lines have a trailing "\r".
> 
> I've noticed that the child-shell-environment procedure is misbehaving on my
> computer because the lines returned by read-line do not have a trailing "\r".
> In the past, I recall that such lines did in fact have a trailing "\r".  I'm
> not sure why it changed, but it seems prudent to just rewrite this code to
> tolerate both cases, since it seems that both cases can happen.
> 
> * guix/scripts/environment.scm (child-shell-environment) [lines]: Instead of
> checking if the line exactly matches "GUIX_CHECK_DONE\r"; check if the line
> begins with "GUIX_CHECK_DONE".  Instead of always stripping the trailing
> character from the line, only do it if the line has a trailing "\r".
> ---
>  guix/scripts/environment.scm | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
> index f0cb341aab..1fb4f5b7c6 100644
> --- a/guix/scripts/environment.scm
> +++ b/guix/scripts/environment.scm
> @@ -462,13 +462,18 @@ (define lines
>                            ;; prompt from getting mixed into what we read.
>                            (match (read-line shell-pipe-in)
>                              ((? eof-object?) (reverse lines))
> -                            ("GUIX-CHECK-DONE\r"
> +                            ((? (lambda (line)
> +                                  ;; The line might or might not have a trailing \r.
> +                                  (string-prefix? "GUIX-CHECK-DONE" line)))
>                               (display "done\n" port)
>                               (reverse lines))
>                              (line
> -                             ;; Drop the '\r' from LINE.
> -                             (loop (cons (string-drop-right line 1)
> -                                         lines))))))))
> +                             ;; Strip the trailing '\r' from LINE if present.
> +                             (let ((stripped-line
> +                                    (if (string-suffix? "\r" line)
> +                                        (string-drop-right line 1)
> +                                        line)))
> +                               (loop (cons stripped-line lines)))))))))
>           (close-port port)
>           (close-port shell-pipe-in)
>           (waitpid pid)
> -- 
> 2.34.0
>