Subject: bug#64858: ~guix shell -C -f guix.scm …~ should not always need ~--rebuild-cache~ option to build the expected environment.

From: Pierre-Henry Fröhring <[email-masked]>
Date: Tue, 25 Jul 2023 16:01:32 +0200

Hello Guix!

As discussed the [[
https://logs.guix.gnu.org/guix/2023-07-21.log#142414][other day]], I'm
providing a more detailed description
(see below) of the unexpected behaviour and an archive containing
enough material to reproduce the bug.

* Experiment
** pkgex-1 -> /gnu/store/0yk3xz85…

The Guix package ~pkgex-1~ is built then its path (~/gnu/store/0yk3xz85…~)
is
shown from within a container (~guix shell -C -f guix.scm ripgrep fd
coreutils
emacs~).

#+begin_example
$ make build # equivalent to: guix build -f guix.scm
…
$ guix shell -C -f guix.scm ripgrep fd coreutils emacs
[env]$ ls -al $EMACSLOADPATH/
total 32
dr-xr-xr-x 2 65534 overflow 4096 Jan  1  1970 .
dr-xr-xr-x 3 65534 overflow 4096 Jan  1  1970 ..
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 guix-emacs.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 guix-emacs.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.elc
lrwxrwxrwx 1 65534 overflow   81 Jan  1  1970 pkgex-1 ->
/gnu/store/0yk3xz85gamig58iska1py6rvn9924ss-pkgex-1/share/emacs/site-lisp/pkgex-1
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 site-start.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 site-start.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.elc
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 subdirs.el ->
/gnu/store/75z28mg9fd0v3mjcg3jmrah9ihnziqcb-emacs-subdirs/share/emacs/site-lisp/subdirs.el
#+end_example

** /gnu/store/8k18bghzcijbps8kix3wqp34x4smfc5l-pkgex-1

This very file (~pkgex.el.org~) is updated with this content then the
package is
built again.

#+begin_example
$ make build # equivalent to: guix build -f guix.scm
…
/gnu/store/8k18bghzcijbps8kix3wqp34x4smfc5l-pkgex-1
#+end_example

** pkgex-1 -> /gnu/store/0yk3xz85…

Unexpectedly, the package linked from within the container using the same
command as above is not updated, we observe:

- ~pkgex-1 -> /gnu/store/0yk3xz85…~

instead of:

- ~pkgex-1 -> /gnu/store/8k18bghz…~

#+begin_example
$ guix shell -C -f guix.scm ripgrep fd coreutils emacs
[env]$ ls -al $EMACSLOADPATH/
total 32
dr-xr-xr-x 2 65534 overflow 4096 Jan  1  1970 .
dr-xr-xr-x 3 65534 overflow 4096 Jan  1  1970 ..
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 guix-emacs.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 guix-emacs.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.elc
lrwxrwxrwx 1 65534 overflow   81 Jan  1  1970 pkgex-1 ->
/gnu/store/0yk3xz85gamig58iska1py6rvn9924ss-pkgex-1/share/emacs/site-lisp/pkgex-1
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 site-start.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 site-start.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.elc
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 subdirs.el ->
/gnu/store/75z28mg9fd0v3mjcg3jmrah9ihnziqcb-emacs-subdirs/share/emacs/site-lisp/subdirs.el
#+end_example

** pkgex-1 -> /gnu/store/8k18bghz…

Nevertheless, if we build a new environment (because we added the
~tree~ package), then, the newly built package
(~/gnu/store/8k18bghz…~) is taken into account.

#+begin_example
$ guix shell -C -f guix.scm ripgrep fd coreutils emacs tree
…
[env]$ ls -al $EMACSLOADPATH/
total 32
dr-xr-xr-x 2 65534 overflow 4096 Jan  1  1970 .
dr-xr-xr-x 3 65534 overflow 4096 Jan  1  1970 ..
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 guix-emacs.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 guix-emacs.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/guix-emacs.elc
lrwxrwxrwx 1 65534 overflow   81 Jan  1  1970 pkgex-1 ->
/gnu/store/8k18bghzcijbps8kix3wqp34x4smfc5l-pkgex-1/share/emacs/site-lisp/pkgex-1
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 site-start.el ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.el
lrwxrwxrwx 1 65534 overflow   91 Jan  1  1970 site-start.elc ->
/gnu/store/0ibk105zcyg27i9gifbf3lhgm6n78z66-emacs-28.2/share/emacs/site-lisp/site-start.elc
lrwxrwxrwx 1 65534 overflow   90 Jan  1  1970 subdirs.el ->
/gnu/store/n7yizf59v4gvjlr66swh3q3kkz3v1vag-emacs-subdirs/share/emacs/site-lisp/subdirs.el
#+end_example