Subject: [bug#57717] [DRAFT PATCH core-updates] build-systems: Pass #:allowed-references and #:disallowed-references to builders.

From: Ludovic Courtès <[email-masked]>
Date: Sun, 11 Sep 2022 16:12:44 +0200

Hi,

Marius Bakke <[email-masked]> skribis:

> * guix/build-system/gnu.scm (gnu-build, gnu-cross-build)[builder]: Pass
> along #:allowed-references and #:disallowed-references.
> * guix/build-system/meson.scm (meson-build, meson-cross-build)[builder]: Likewise.
> ---
> Hello Guix,
>
> This is an untested patch that makes #:allowed-references
> and #:disallowed-references available to build-side code.
>
> The intention is to make it easier to use these properties directly when
> e.g. wrapping.  Consider the following:
>
> (arguments
>  (list
>   #:disallowed-references (list (gexp-input glib "bin")
>                                 (gexp-input inkscape/stable))
>   #:phases
>   #~(modify-phases %standard-phases
>      (replace 'glib-or-gtk-wrap
>        (let ((wrap (assoc-ref %standard-phases 'glib-or-gtk-wrap)))
>          (lambda* (#:key inputs outputs disallowed-references
>                    #:allow-other-keys)
>                  (wrap #:inputs (filter (match-lambda
>                                           ((label . output)
>                                            (not (member output
>                                                         disallowed-references))))
>                                         inputs)
>                        #:outputs outputs)))))))
>
>
> This way we don't have to build the list of disallowed references twice,
> which is difficult without labels in the case of e.g. `(,glib "bin").

Why not.

The only possible drawback I can think of is that it could hide errors:
since things listed in #:disallowed-references are automatically removed
from wrappers, you could end up successfully building a wrapper that
lacks items without noticing.  But yeah, maybe that’s a questionable
scenario.

> +                           #:allowed-references #$allowed-references
> +                           #:disallowed-references #$disallowed-references

Maxime raised a good point on this one, but I think you can write:

  #:disallowed-references '#$disallowed-references

This will work whether ‘disallowed-references’ is #f or a list.

Thanks!

Ludo’.