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

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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.
This commit is contained in:
zimbatm 2024-09-01 12:06:30 +02:00
parent dd6c0ee128
commit 1ea32d4f69
1 changed files with 3 additions and 3 deletions
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6
nixos/modules/system/boot/loader/grub/grub.nix
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@ -712,9 +712,9 @@ in
(mkIf cfg.enable {
boot.loader.grub.devices = optional (cfg.device != "") cfg.device;
boot.loader.grub.devices = mkIf (cfg.device != "") [ cfg.device ];
boot.loader.grub.mirroredBoots = optionals (cfg.devices != [ ]) [
boot.loader.grub.mirroredBoots = mkIf (cfg.devices != [ ]) [
{ path = "/boot"; inherit (cfg) devices; inherit (efi) efiSysMountPoint; }
];
@ -752,7 +752,7 @@ in
# set at once.
system.boot.loader.id = "grub";
environment.systemPackages = optional (grub != null) grub;
environment.systemPackages = mkIf (grub != null) [ grub ];
boot.loader.grub.extraPrepareConfig =
concatStrings (mapAttrsToList (n: v: ''