If the user has enabled the XDG user directories module then we can
use the XDG music directory in the MPD module. Otherwise we'll leave
the option undefined so that the user is forced to define the
directory to use.
This applies to state version 22.11 and above.
Fixes#3225
Before, loading a module would be guarded by an optional platform
condition. This made it possible to avoid loading and evaluating a
module if it did not support the host platform.
Unfortunately, this made it impossible to share a single configuration
between GNU/Linux and Darwin hosts, which some wish to do.
This removes the conditional load and instead inserts host platform
assertions in the modules that are platform specific.
Fixes#1906
This allows specifying, for example, the music directory using path
literals without causing the directory to be copied to the Nix store.
Suggested-by: Silvan Mosberger <infinisil@icloud.com>
MPD is using syslog for its logging output, while it could directly
log to systemd's journal, as this daemon is primarily used as a
systemd user service. This change makes MPD log to standard output,
which is captured by systemd.
See https://github.com/NixOS/nixpkgs/pull/57608, which does the same
thing to NixOS's MPD service.
