bug#71941: [PATCH] guix: fix map-derivation not handling directories

["Sergio Pastor Pérez" <sergio.pastorperez@outlook.es>]

The `map-derivation` procedure was trying to process directories as files.
When a derivation had a 'module import' directory as input, it threw an
exception since it tried to open it as a file.

Change-Id: I9b766f9aaa03ea9307f73e8abb36bc347af4b5e6
---
Hi, as far as I know 'module import' directories don't contain derivation
references, so it should not be needed to apply `substitute-file` on the files of
those directories. This fix just returns the 'module import' directories
untouched. Thoughts?

Note that `map-derivation` is very slow. I could only test it with tiny
derivations, such as the ones provided in the '(gnu packages commencement)'
module.

You can test it with:
--8<---------------cut here---------------start------------->8---
scheme@(guix-user)> (use-modules (guix store)
                                  (guix packages)
                                  (guix derivations)
                                  (gnu packages games)
                                  (gnu packages bootstrap))
scheme@(guix-user)> (with-store store
                      (let ((bootar-drv (package-derivation store (@@ (gnu packages commencement) bootar)))
                            (guile-bootstrap-drv (package-derivation store %bootstrap-guile))
                            (cowsay-drv (package-derivation store cowsay)))
                        (map-derivation store
                                        bootar-drv
                                        `((,guile-bootstrap-drv . ,cowsay-drv)))))
$1 = #<derivation /gnu/store/qwn18yxc1ccdxq1mgg863lfxsfwng3wk-bootar-1b.drv => /gnu/store/852xy3bhck2sd1hq1rmzai0px7fplxfq-bootar-1b 7fcfc3f05b90>
scheme@(guix-user)> (derivation-inputs $1)
$2 = (#<<derivation-input> drv: #<derivation /gnu/store/5rx5dn2xnkjs3q0rzpm66q79ndwrafp7-module-import-compiled.drv => /gnu/store/472plnlfm8yrb3axwy16fydq01idbkv1-module-import-compiled 7fcfc3f05d70> sub-derivations: ("out")> #<<derivation-input> drv: #<derivation /gnu/store/fhqh9f3lmf8wd9mh0bzavpkjnmsb0bg0-cowsay-3.7.0.drv => /gnu/store/vwa9vh21l68ivnwxj18s2gxd1v71w43r-cowsay-3.7.0 7fcfb73a50f0> sub-derivations: ("out")> #<<derivation-input> drv: #<derivation /gnu/store/k6852ja7cvdvbbdxh24ph711gm74m3qq-bootar-1b.ses.drv => /gnu/store/xmw3h03svpw6rwfg03f0m608zkm24qx8-bootar-1b.ses 7fcfc3f05f00> sub-derivations: ("out")>)
--8<---------------cut here---------------end--------------->8---

As you can see, with this fix, the new derivation has the `cowsay` package a an
input.

I would like to encourage people to discuss ways to improve the performance of
this procedure. It would be very useful for system wide package rewriting as
discussed in this thread[1].

[1]: https://lists.gnu.org/archive/html/guix-devel/2024-06/msg00275.html

Regards,
Sergio.


 guix/derivations.scm | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/guix/derivations.scm b/guix/derivations.scm
index a91c1ae984..c16e1c2be3 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -1062,8 +1062,10 @@ (define* (map-derivation store drv mapping
                                     ((_ . replacement)
                                      replacement)
                                     (#f
-                                     (substitute-file source
-                                                      initial replacements))))
+                                     (if (file-is-directory? source)
+                                         source
+                                         (substitute-file source
+                                                          initial replacements)))))
                                 (derivation-sources drv)))
 
              ;; Now augment the lists of initials and replacements.

base-commit: e1c92c98f7afff13fb7060199ba0dd4d9c5c2c53
-- 
2.45.2