Re: [bug#42738] [PATCH v4] gnu: emacs: Update to 27.1.

[Mark H Weaver <mhw@netris.org>]

Hi Ludovic,

Ludovic Courtès <ludo@gnu.org> wrote:
> Mark H Weaver <mhw@netris.org> skribis:
>
>> (define-public emacs-next
>>   (let ((commit "c36c5a3dedbb2e0349be1b6c3b7567ea7b594f1c")
>>         (revision "0")
>>         (emacs-version "27.0.91"))
>>     (package
>>       (inherit emacs)
>>       (name "emacs-next")
>>       (version (git-version emacs-version revision commit))
>>       (source
>>        (origin
>>          (inherit (package-source emacs))
>>          (method git-fetch)
>>          (uri (git-reference
>>                (url "https://git.savannah.gnu.org/git/emacs.git")
>>                (commit commit)))
>
> This can be handled with ‘--with-git-url’.

I think that wouldn't work in this case, because we also need to
preserve the existing 'patches' and 'snippet' fields, which I arranged
to inherit above via (inherit (package-source emacs)).  That probably
deserves a comment, since it's easily overlooked.

>>          (sha256
>>           (base32 "0mlrg2npy1r79laahkgzhxd1qassfcdz8qk1cpw7mqgf6y5x505h"))
>>          (file-name (git-file-name name version))))
>>       (native-inputs
>>        `(("autoconf" ,autoconf)      ; needed when building from trunk
>>          ,@(package-native-inputs emacs)))
>
> For this, we’d need a new ‘--with-extra-input’ package transformation
> option or similar.  That way, we wouldn’t even need an ‘emacs-next’
> package: people would just run
>
>   guix install emacs --with-git-url=… --with-extra-input=autoconf

There's also the 'native-search-paths' field, which cannot simply be
inherited because of the version number embedded within EMACSLOADPATH.
This particular issue could be avoided if the 'native-search-paths'
field were a function of the version number, but that raises migration
issues and I'm not sure it's worth it.

What do you think?

    Best regards,
        Mark