(propagated) 'inputs' depends on 'outputs'?

[zimoun]

Dear,

My question is: is it possible to specify 'inputs' only for specific 'outputs'?

Well, I think that the answer is no because build-time vs install-time
but I could have wrong and/or someone could have a fix for me. :-)


As an exemple, give a look at the package "git".  Because it has
several 'outputs' ("send-email", "svn", etc.), the list of "inputs"
provides e.g., "subversion" even if I am only interested by
"git:send-email".  This matters about closure (bandwidth, rebuild,
etc.).

I do not have an example at hand, but I think that if one package has
2 outputs '("out" "doc")' and the documentation requires heavy TeX
then I cannot work only on the "out" without downloading all the
documentation dependencies, i.e.,

   guix environment foo

could eat all my resources even if I am not interested by the
documentation part.


Another example is the package "emacs-helm-bibtex" which propagated
both Helm and Ivy completion backends.  Well, for example if the
'outputs' list is '("out" "helm" "ivy")' then the user could install
only the Ivy backend with:

   guix install emacs-helm-bibtex:ivy

without propagating the full 'emacs-helm' package.  Well, from my
understanding, the way is to create another package using 'inherit'
and remove the unnecessary part and then install with:

   guix install emacs-helm-bibtex-ivy

And same strategy the former Git example.


Well, it is already possible to test of some variables and set
different inputs,  See for example the package 'ncurse'.  Hopefully it
is possible because it is intensively used for cross-compiling. :-)


Thank you in advance for any tips. :-)

All the best,
simon