nixos/swraid: only warn if swraid was explicitly enabled (#255426)

The default just recently changed in 23.11. Users that had
swraid enabled implicitly by NixOS in previous releases got surprised
by warnings even though they do not actually use software RAID.

Fixes #254807

1 files changed, 7 insertions, 2 deletions

diff --git a/nixos/modules/tasks/swraid.nix b/nixos/modules/tasks/swraid.nix
index 1174187062d..61b3682e0f6 100644
--- a/nixos/modules/tasks/swraid.nix
+++ b/nixos/modules/tasks/swraid.nix
@@ -4,6 +4,11 @@
 
   mdadm_conf = config.environment.etc."mdadm.conf";
 
+  enable_implicitly_for_old_state_versions = lib.versionOlder config.system.stateVersion "23.11";
+
+  minimum_config_is_set = config_text:
+    (builtins.match ".*(MAILADDR|PROGRAM).*" mdadm_conf.text) != null;
+
 in {
   imports = [
     (lib.mkRenamedOptionModule [ "boot" "initrd" "services" "swraid" "enable" ] [ "boot" "swraid" "enable" ])
@@ -26,7 +31,7 @@ in {
         should detect it correctly in the standard installation
         procedure.
       '';
-      default = lib.versionOlder config.system.stateVersion "23.11";
+      default = enable_implicitly_for_old_state_versions;
       defaultText = lib.mdDoc "`true` if stateVersion is older than 23.11";
     };
 
@@ -39,7 +44,7 @@ in {
 
   config = lib.mkIf cfg.enable {
     warnings = lib.mkIf
-        ((builtins.match ".*(MAILADDR|PROGRAM).*" mdadm_conf.text) == null)
+        ( !enable_implicitly_for_old_state_versions && !minimum_config_is_set mdadm_conf)
         [ "mdadm: Neither MAILADDR nor PROGRAM has been set. This will cause the `mdmon` service to crash." ];
 
     environment.systemPackages = [ pkgs.mdadm ];