nixos/grub: fix value precendence with optional -> mkIf

When using `lib.optionals`, the return value of both branches of the
condition get set as a value to the option.

When using `lib.mkIf`, only the positive condition gets set as a value
to the option.

This small distinction is important when dealing with precedence. For
example here, we wanted to set a boot.grub.devices default value with
lib.mkDefault, and that was getting overridden with the empty value of
`lib.optional (cfg.device != "") cfg.device`.

See https://github.com/nix-community/srvos/pull/491#discussion_r1738827651

The general conclusion is that using `lib.mkIf` is preferable to
`lib.optional` or `lib.optionals` when setting values in the NixOS
module system.

0 files changed, 0 insertions, 0 deletions