Re: XDG Base Directory Specification ignores installation directories

[Patrice Dumas]

On Wed, Sep 25, 2024 at 06:54:12PM +0100, Gavin Smith wrote:
> I understand the idea of files in datadir not being edited, although
> I am still not really sure what the purpose of XDG_DATA_DIRS is (in
> general, not just as it relates to Texinfo).  According to the XDG
> Specification, this is /usr/local/share:/usr/share by default, which is
> where the files are installed by the package as an integral part of the
> program.  This corresponds to the ${datadir} of the GNU Coding Standards.
> I do not understand why anyone would set XDG_DATA_DIRS.
> 
> It seems that XDG_DATA_DIRS (and XDG_CONFIG_DIRS) are already set on
> my system (Linux Mint 21.2 Xfce, which is an Ubuntu derivative) when I
> log in.  If this is frequent, then it causes problems for people installing
> to non-standard ${datadir} (and ${sysconfdir}) where files in the wrong
> locations would be used if these variables take priority over compiled-in
> values.

My understanding is that if you want to install on non-standard
locations and want to have this non-standard location being searched for
before other directories, then you should put first in XDG_DATA_DIRS (or
XDG_CONFIG_DIRS).  It should be possible to change
XDG_DATA_DIRS/XDG_CONFIG_DIRS as a user or for the system, but it
depends on the platform configuration.  It seems to often be in
/etc/profile.d/ for system-wide early change of environment variables
for GNU/Linux.

> Could we consider ignoring the XDG_DATA_DIRS and XDG_CONFIG_DIRS part
> of the specification?  (It seems that XDG_DATA_HOME and XDG_CONFIG_HOME
> are the part that people really care about.)

It seems to me that being able to set the search paths are a good thing.
They should be adustable if they are set by the distribution.

> We could try discussing with developers of other GNU packages what
> they do about these variables, and how the XDG specification works
> with the GNU Coding Standards and existing practice.

That could be possible.

As a side note, I am not sure that it is very useful, but I tried to
raise one issue I saw with inconsistency between $datadir/...  and
directories searched for in the XDG specification on the Xdg info list.
There was some discussion and, in addition to my proposals a proposal to
remove completly reference to $datadir in the specification to avoid the
issue:

 https://lists.freedesktop.org/archives/xdg/2024-August/014748.html
 https://lists.freedesktop.org/archives/xdg/2024-August/014754.html

It was not followed by any action, be it a rejection, nor more
discussion nor implementation.  It is not actually clear too me, now,
that this list is really the place to discuss freedesktop.org's
standards and specifications.

-- 
Pat