Hi all,

Sorry to tell this - I don't think something like this would be even
possible to implement :/

AFAIK package definition fields like `(inputs)` don't just describe how
the package gets installed. They affect the actual build. So if we
really wanted this feature, we'd need to build 2 separate variants of a
package - one for Guix system and one for foreign distros.

In addition to looking like an overkill, such separate build variants
could also require changes to existing utilities like `guix copy`.

Besides all this, It it not that easy to determine whether Guix is
running under a foreign distro. One idea would be to check whether the
currently-running init system is Shepherd. But what if the user is
running Guix commands inside a Guix system chroot? The Shepherd process
is not going to be visible in such case

Wojtek

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On Wed, 23 Nov 2022 18:36:49 +0800
Zhu Zihao <all_but_last@163.com> wrote:

> If you want to left the choice to user. You can just don't patch it. Or
> you can always patch it because user can still use package transformer
> to specify a custom ffmpeg.
> 
> 
> jgart <jgart@dismail.de> writes:
> 
> > Does Guix have a declarative Guix API way of knowing if it is installing
> > a package into foreign distro versus Guix System?
> >
> > I'm thinking of a function like `foreign-distro?`:
> >
> > ```
> > (define-public peek
> >   (package
> >    (name "peek")
> >    ...
> > (inputs 
> >   `(,@(if (foreign-distro?) `(("ffmpeg" ,ffmpeg)) '())))
> > ```
> >
> > The above includes ffmpeg in the inputs only if installing peek on a
> > foreign distro. It could additionally patch the ffmpeg executable in
> > a peek package phases if foreign-distro? returns #t.
> >
> > WDYT  
> 
>