GNU bug report logs - #65665
package-mapping with #:deep? #t doesn't get all the implicit inputs

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: Ulf Herrman <striness <at> tilde.club>
Cc: dev <at> jpoiret.xyz, zimon.toutoune <at> gmail.com, othacehe <at> gnu.org, ludo <at> gnu.org, me <at> tobias.gr, 65665 <at> debbugs.gnu.org, rekado <at> elephly.net, guix <at> cbaines.net
Subject: bug#65665: package-mapping with #:deep? #t doesn't get all the implicit inputs
Date: Sun, 03 Sep 2023 09:02:31 -0400

Hello Ulf,

Ulf Herrman <striness <at> tilde.club> writes:

> #:deep? #t currently works by interposing a dummy build system that
> lowers the package to a bag using the original build system, then
> applies the supplied transformation to all of the bag's inputs, then
> returns a new bag with the new inputs.
>
> The problem with this approach is that it doesn't affect the bag
> arguments.  This means that packages passed in as arguments may still
> end up being used without being transformed.  Worse still, packages
> *not* passed in as arguments may end up being used *unless one is
> explicitly passed in as an argument*, as is the case with
> qt-build-system's #:qtbase argument.
>
> In short, the current approach of having the build-system lower
> procedure leave the arguments mostly unchanged and letting the
> bag->derivation procedure (the "bag builder") fill in lots of defaults
> means that there are implicit inputs that cannot be touched at the
> package level without adding special logic for every single build system
> that does something like this.

This is indeed sub-optimal!

> I propose that we have the build system lower procedure (that is, the
> one that converts from package to bag) completely fill in the argument
> list with all defaults, and we modify build-system-with-package-mapping
> to transform all arguments that look like a package or a list of
> packages (or maybe even a tree containing packages).

[...]

> What do you think?

Like Csepp, I like your proposition!  I'm CC'ing the core team, in case
they have something to add to it, but otherwise, we only need a
volunteer to turn it into code :-).

-- 
Thanks,
Maxim

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