[bug#38616] emacs: fix odt export

[Jelle Licht <jlicht@fsfe.org>]

Hello Nicholò,

anothersms@gmail.com (Nicolò Balzarotti) writes:

> Hello Guix!
>
> Neither on NixOS or in guix I've ever been able to export an org file to
> otd. The error was
> 'OpenDocument export failed: Buffer is read-only: #<killed buffer>'.
>
> I've seen some report of this error on the web, like:
> - https://lists.gnu.org/archive/html/emacs-orgmode/2018-05/msg00545.html
> - https://github.com/syl20bnr/spacemacs/issues/1482
>
> but also on our IRC:
> - http://logs.guix.gnu.org/guix/2019-05-07.log
> - http://logs.guix.gnu.org/guix/2019-07-25.log
> but I was not able to find a fix for it.
>
> Today I checked the source and figured it out. The explanation, as
> written in the patch, is the following
>
>> Files inside the guix store are read only. "styles.xml" is copied from the
>> store (/share/emacs/26.3/etc/org/OrgOdtStyles.xml), so it's read only too.
>> ox-odt needs this file, so if it's not writable it will fail. This patch
>> adjust the permissions.
Thanks for figuring this out! I've been using my local (terrible)
workarounds for years to make this work.

>
> So, this patches fixes the permissions on the file.
>
> I've two questions:
> 1. Is it fine to have a .patch, or should I add a phase where I fix the
>    file? this seemed to be easier

I can't really advise on the best way forward here, but if you do decide
to go with the .patch route, you should probably also add your .patch
file to `dist_patch_DATA' in gnu/local.mk.

> 2. If the same error happens for other programs, might it make sense to
>    "fake" rw permissions in the store (by using a virtual fs or
>    something) so that files are copied as rw, but files in the store are
>    still ro?

IMHO, software shouldn't assume certain permissions are set, and instead
check or make-it-so. Perhaps you could upstream your patch instead of
embedding it into Guix?

Furthermore, the same issue as the one your fixed here is also present
in our `emacs-org' package. Do you think your approach would work there
as well? If so, it might make sense to fix both emacs and emacs-org.

Thanks!
- Jelle