bug#27686: emacs-ess: Not installed in "${output}/share/emacs/site-lisp/guix.d"

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

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Hi,

On Tue, Jul 18, 2017 at 9:52 AM, Alex Kost <alezost@gmail.com> wrote:

> Adonay Felipe Nogueira (2017-07-13 09:20 -0300) wrote:
>
> > It seems that Emacs ESS mode isn't installed in the same location as
> > other packages are.
> >
> > Also note that emacs-ess doesn't use the Emacs build system. I don't
> > know if this is indeed the issue (and if we can force it to use such
> > build system), but I think this is an important note to make.
>
> It's not a problem: we just need to install *.el files in
> ".../share/emacs/site-lisp/guix.d/ess" instead of
> ".../share/emacs/site-lisp/ess" as it is done by default.  The attached
> patch should fix it.
>
> A side note: this is one of the reasons why I don't like "guix.d"
> sub-directory.  I think it is a useless extra level in the file
> hierarchy.  If we used:
>
>   .../share/emacs/site-lisp/<package>
>

While I agree that packaging elisp files in their own folder is cleaner, it
also introduces some complexity such as the requirement to add some glue
code in the Emacs site-start.el for packages discovery. This mechanism is
only valid when working with a profile; at build time (say, you want to run
tests which depend on other Emacs packages), another hack is required +
manual fiddling.

By contrast, if all of our Emacs packages were laid out flat under the
usual share/emacs/site-lisp/ like it's done on other distributions, we
could simply define the EMACSLOADPATH `search-path' at the Emacs package
definition level, and the rest would be taken care of by Guix native
mechanisms (no hacks required).

IMHO, this would be more "Guixy".

Alternatively, we would need to extend the seacrh-path facility to be able
to deal with our own added complexity. I'm not sure if it's worth it.

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