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

* 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:

--8<---------------cut here---------------start------------->8---
(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)))))))
--8<---------------cut here---------------end--------------->8---

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").

Note: I implemented a variant of this approach using a let-binding in
f0114656876dcf2e09874e4ea0c00cacf31f1bb2, perhaps that is "good enough"
as this approach is unlikely to be much used.

WDYT?  I'll implement this for the remaining build systems if this is at
all sane.
---

On 10-09-2022 17:26, Marius Bakke wrote:
> 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").
> 
> Note: I implemented a variant of this approach using a let-binding in
> f0114656876dcf2e09874e4ea0c00cacf31f1bb2, perhaps that is "good enough"
> as this approach is unlikely to be much used.
> 
> WDYT?  I'll implement this for the remaining build systems if this is at
> all sane.

A caveat with using #:disallowed-references this way -- AFAIK, it is 
undocumented whether #:disallowed-references goes for a native build or 
a cross-build.  The intention is to stop the (natively-)compiled 
python-some-testing-library from appearing in the wrappers, stopping a 
cross-compiled python-some-testing-library.

Depending on what, exactly, the behaviour of #:disallowed-references is, 
it may be necessary to ‘override’ whether to disallow the native- or the 
cross-version.

To do so, I used 'gexp-input' with #:native? #true in (gnu packages 
glib) (maybe that was unnecessary, but I was thinking better be explicit 
than implicit here ...).

An alternative solution could be to split #:disallowed-reference in two, 
e.g. #:disallowed-references/system and #:disallowed-references/target, 
to prevent accidents.

Greetings,
Maxime.

On 10-09-2022 17:26, Marius Bakke wrote:
> +                           #:allowed-references #$allowed-references
> +                           #:disallowed-references #$disallowed-references

Unless I'm mistaken (I haven't tested this), this will become 
#:allowed-references ("/gnu/store/..." ...) -- it tries to use a string 
as a procedure.  Proposal:

#:allowed-references (list #$allowed-references)
#:disallowed-references (list #$disallowed-references)

Greetings,
Maxime.

On 10-09-2022 18:32, Maxime Devos wrote:
> 
> 
> On 10-09-2022 17:26, Marius Bakke wrote:
>> +                           #:allowed-references #$allowed-references
>> +                           #:disallowed-references 
>> #$disallowed-references
> 
> Unless I'm mistaken (I haven't tested this), this will become 
> #:allowed-references ("/gnu/store/..." ...) -- it tries to use a string 
> as a procedure.  Proposal:
> 
> #:allowed-references (list #$allowed-references)
> #:disallowed-references (list #$disallowed-references)

Correction:

#:allowed-references
#$(and=> allowed-references (lambda (x) #~(list #$@x)))
#:disallowed-references
(list #$@disallowed-references)

(splicing, and allowed-reference is by default #false)

> Greetings,
> Maxime.

Hi,

Marius Bakke <marius@gnu.org> 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’.