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

[Ludovic Courtès]

Hi Ulf,

Ulf Herrman <striness@tilde.club> skribis:

> 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.

Could you share an example of what is fixed by these changes?

Let’s take ‘python-itsdangerous’ as an example.  It has zero inputs,
only implicit dependencies, yet I can do this:

--8<---------------cut here---------------start------------->8---
$ guix build python-itsdangerous -n
substitute: updating substitutes from 'http://192.168.1.48:8123'... 100.0%
0.0 MB would be downloaded:
  /gnu/store/yhvhrmqd5znjs7vsq8kc55nc3rkg4w6x-python-itsdangerous-2.0.1

$ guix build python-itsdangerous --with-input=python=python2 -n
The following derivations would be built:
  /gnu/store/b1hji2qzdiwfg2wx11l1fyjrgiy0f50v-python-itsdangerous-2.0.1.drv
  /gnu/store/5gibs6x75acc6j0g0rh8m66191l9wq12-python-wrapper-3.10.7.drv
0.1 MB would be downloaded:
  /gnu/store/b2qv97jbih850zn35b2j84n2acj079cv-itsdangerous-2.0.1.tar.gz

$ guix gc --references 
/gnu/store/5gibs6x75acc6j0g0rh8m66191l9wq12-python-wrapper-3.10.7.drv |grep 
python
/gnu/store/n0snl506x5bbs5c2496blh79yil3pf44-python2-2.7.18.drv
/gnu/store/whwrah24q7syyiqra16sm9mjvdxld1pv-python-wrapper-3.10.7-builder
--8<---------------cut here---------------end--------------->8---

‘python’ above is an implicit dependency, yet it was suitably replaced
by ‘--with-input’.

In what cases does ‘package-mapping #:deep? #t’ miss implicit inputs?

Thanks,
Ludo’.