Re: Optional runtime dependencies in Guix

[宋文武 <iyzsong@gmail.com>]

Ludovic Courtès <ludo@gnu.org> writes:

> Gammel Holte <gammel.holte@gmail.com> skribis:
>
>> For example, consider samtools, a package I use daily and that was recently
>> committed to Guix:
>>
>> http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/bioinformatics.scm#n139
>>
>> It forces me to install python. In contrast, consider Arch AUR's package:
>>
>> https://aur.archlinux.org/packages/samtools/
>
> From looking at the page above, it seems that it would be feasible to
> simply move varfilter.py to a different output.  That way, users would
> be able to install the default output (which doesn’t depend on Python),
> or the “python” output.  Ricardo, WDYT?
Move it to a different output should work, but the 'python' output
doesn't make much sense to me compare to 'doc', 'bin' and 'debug'.

Note that 'python' is not a build dependency of 'samtools', so we
can only patch '#!/usr/bin/env' but not 'python' for varfilter.py.
Then we should give recommends or suggests, user need it could
install python manually.
>
>> An extreme example of this is weechat:
>>
>> http://lists.gnu.org/archive/html/guix-devel/2014-09/msg00229.html
>>
>> Compare with:
>>
>> https://www.archlinux.org/packages/extra/i686/weechat/
>>
>> Guix version forces the user to install all interpreters for running
>> user-defined scripts to extend Weechat. These are quite many: lua, perl,
>> python, ruby, tcl (and guile).
>
> Yes, I hadn’t noticed this and I agree this is problematic.
>
> Kevin, any idea on how to split things?
This is total different, those plugins must live in $out/lib/plugins
to work (can't move to seperated outputs).
Keep in mind that interpreters are both build and runtime dependencies
of weechat, the nature way is making them optional when building:

  (define-public (%weechat #:key (python? #t)
                                 (guile?  #t)
                                ...
    (package
      (inputs
      `(("python" ,(if python? python #nil))
        ("guile"  ,(if guile?  guile  #nil))
    ...
       

  (define-public weechat (%weechat)) ; our default version

Then user can install the customized version with:
  $ guix package -e '((@ (gnu packages weechat) %weechat) #:python? #f)'
>
> As I wrote before, there’s no one-size-fits-all recipe to address the
> problem, just a couple of usable patterns (basically separate outputs or
> separate packages.)  So we need to address this mostly on a case-by-case
> basis, and also probably clarify this in the packaging guidelines.
>
> Thanks,
> Ludo’.