XDG_CONFIG_DIRS an /usr/local/etc/xdg

[Peter White]

On Thu, Sep 16, 2021 at 01:10:30AM -0400, Elsie Hupp wrote:
> I’m by no means an expert on this, but it may be possible that by not
> implementing XDG_CONFIG_DIRS the distros’ intention may be for
> applications to use, for example, XDG_CONFIG_HOME instead. It may be
> worth asking your distro’s maintainers why the variable is unset.

The reason might very well be the possibly unexpected behaviour I
mentioned. XDG_CONFIG_DIRS acts like PATH does: first match wins, which
I would not expect to happen with conffiles. As I said I expect local
software to pick its conf from the local prefix and distro provided
software to use an empty prefix for /etc, exclusively.

> By comparison, looking at the Flatpak documentation, for example, they
> don’t even mention XDG_CONFIG_DIRS:
> 
> https://docs.flatpak.org/en/latest/conventions.html?#xdg-base-directories
> 
> …though Flatpak is specifically intended to be sandboxed, so their
> environmental variables are set internally, and system-level writable
> directories are generally discouraged.

I think that's why: you cannot write inside such a container, so system-
wide configs cannot be changed. XDG_CONFIG_HOME has the problem, that
one cannot provide a default for everyone, which is the purpose of a
system-wide config and it cannot be installed by make install, unless
each user installs the software to $HOME/.local. Now, that can't be
right. ;)

> If you need to use /usr/local/etc/xdg instead of /etc/xdg specifically
> in order to work with a different, pre-existing application, it may be
> worth looking at that application’s code and asking its developers
> about it, as well.

Which is precisely why I am asking. I am in the process of proposing
changes to that project, because it has/had rather peculiar install and
runtime routines, i.e. installing outside PREFIX, overwriting distro
managed files and using /etc (not even /etc/xdg, let alone
/usr/local/etc/xdg), despite them facilitating
g_get_system_config_dirs() to find configs, which suggests,
they want to comply to the spec, but they won't apply my changes yet,
since there is disagreement over where in /usr/local (etc or etc/xdg)
the config should go and how to actually find it at runtime. So I am
asking here for guidance by the folks who should know best, so I can go
back there with authoritative information, hopefully. Something needs to
change, might as well do it right. ;)
I found XDG_CONFIG_DIRS to be unset on Ubuntu and expect that to be the
case for all distributions because of the above mentioned PATH-like
behaviour of this facility. So, either we find a way to make it work
flexibly with XDG_CONFIG_DIRS or it needs to be set an compile time. I
would very much prefer the first option and want to know, if that is
possible or even intended.

> > On Sep 16, 2021, at 12:44 AM, Peter White <peter.white at posteo.net> wrote:
> > 
> > Dear list,
> > 
> > I am having a hard time finding documentation about the best way to make
> > locally installed software recognize its config dir in
> > /usr/local/etc/xdg. Of course, the quick and easy answer could be:
> > 
> >    $ env XDG_CONFIG_DIRS=/usr/local/etc/xdg foobar
> > 
> > But that is not something one can ask their users if they install
> > software from an upstream repository. I believe XDG_CONFIG_DIRS is unset
> > on most systems and thus defaults to /etc/xdg, i.e. returned by
> > g_get_system_config_dirs(), so most people would have to set it manually
> > to make software in /usr/local pick up its config from there, which it
> > should IMO.
> > 
> > One might also think:
> > 
> >    # echo XDG_CONFIG_DIR=/usr/local/etc/xdg:/etc/xdg >> /etc/environment
> > 
> > could be the solution, but I believe that can lead to some unexpected
> > behaviour, when the user also has the distro counterpart of said
> > software installed, i.e. when they installed the local version to test
> > it against the distro version. If they then only change PATH to either
> > prefer the local or the distro version, the latter would also pick the
> > config which is only meant for the local one. The distro version might
> > be outdated an contain obsolete settings.
> > From what other software (i.e. a shell) does, I believe the correct way
> > would be to use the /usr/local/etc/xdg when running a local version and
> > /etc/xdg when running the distro version, if I am not mistaken.
> > 
> > So I guess, my first question is, if XDG_CONFIG_DIRS is even meant to be
> > used by locally installed software, its default seems to suggest
> > otherwise? Or is this maybe just an oversight in the spec? I'd find that
> > hard to believe, given that it's been around for quite a while now, so
> > my thought process may very well be flawed here.
> > 
> > I have pondered this for a while now and could also not find anything
> > via search engine or on this list, so I figured I actually ask the ones
> > who wrote the spec. ;)
> > 
> > 
> > Best,
> > PW
>