This is a follow-up to #188 concerning the second suggestion I made there:

platformdirs.user_runtime_dir() currently yields /run/user/0/… for root on Unix. While not strictly false, this is a rather uncommon result; for root I'd rather expect just /run/….

Due to this @kemzeb just recently added platformdirs.site_runtime_dir() yielding /run/… on Unix (thank you @kemzeb! ❤️). I absolutely think that this is the right approach. However, platformdirs.user_runtime_dir() still yields /run/user/0/… for root on Unix - which is not wrong (it might be the correct answer, see #188), but unexpected.

This gets crucial for software that can run as both unprivileged users, and root, like Borg. For unprivileged users platformdirs.user_runtime_dir() is always the right answer, but for root it's usually platformdirs.site_runtime_dir(). I believe that this is true for most software that can run as both unprivileged users, and root:

[…] root is different: Software running as root is often intentionally NOT bound to root being logged in - in many systems root can't login at all. This is due to root's special role in Unix and a major difference to any other user. […] This doesn't mean that there might not indeed be software whose lifetime is bound to root being logged in [(i.e. platformdirs.user_runtime_dir() is the right answer for root, too)] - but that's the exception rather than the rule.

AFAIK platformdirs doesn't address root's special role in Unix […] right now, but it should.

To better account for root's special role on Unix I'd like to suggest the following:

As additional feature it might be helpful to add a global switch (disabled by default) which basically redirects calls to platformdirs.user_*_dir() to their platformdirs.site_*_dir() equivalent (i.e. not just for user_runtime_dir(), but config, cache, state, … too) for root unless stated otherwise (i.e. add a option to each method next to the global switch).

Even though I believe that most software would want to enable this global switch, I suggest disabling it by default to preserve BC. However, we should document this and the switch's usage.

What are your opinions on this?

Just to make this clear: One can easily implement root's special role in the software using platformdirs, i.e. add such a switch. Thus it's definitely no major issue. However, if you decide not to implement such a switch I'd strongly vote for at least documenting root's special role in Unix and that most projects rather want to use platformdirs.site_*_dir() for root.

Cc: @ThomasWaldmann