grub: add grub.useOSProber option (#22558)

nixos/modules/system/boot/loader/grub/grub.nix

@@ -53,12 +53,14 @@ let
       inherit (args) devices;
       inherit (efi) canTouchEfiVariables;
       inherit (cfg)
-        version extraConfig extraPerEntryConfig extraEntries forceInstall 
+        version extraConfig extraPerEntryConfig extraEntries forceInstall useOSProber
         extraEntriesBeforeNixOS extraPrepareConfig configurationLimit copyKernels
         default fsIdentifier efiSupport efiInstallAsRemovable gfxmodeEfi gfxmodeBios;
       path = (makeBinPath ([
         pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.findutils pkgs.diffutils pkgs.btrfs-progs
-        pkgs.utillinux ] ++ (if cfg.efiSupport && (cfg.version == 2) then [pkgs.efibootmgr ] else [])
+        pkgs.utillinux ]
+        ++ (optional (cfg.efiSupport && (cfg.version == 2)) pkgs.efibootmgr)
+        ++ (optionals cfg.useOSProber [pkgs.busybox pkgs.os-prober])
       )) + ":" + (makeSearchPathOutput "bin" "sbin" [
         pkgs.mdadm pkgs.utillinux
       ]);
@@ -265,6 +267,14 @@ in
         '';
       };
 
+      useOSProber = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          If set to true, append entries for other OSs detected by os-prober.
+        '';
+      };
+
       splashImage = mkOption {
         type = types.nullOr types.path;
         example = literalExample "./my-background.png";

nixos/modules/system/boot/loader/grub/install-grub.pl

@@ -424,10 +424,17 @@ if ($extraPrepareConfig ne "") {
   system((get("shell"), "-c", $extraPrepareConfig));
 }
 
-# Atomically update the GRUB config.
+# write the GRUB config.
 my $confFile = $grubVersion == 1 ? "$bootPath/grub/menu.lst" : "$bootPath/grub/grub.cfg";
 my $tmpFile = $confFile . ".tmp";
 writeFile($tmpFile, $conf);
+
+# Append entries detected by os-prober
+if (get("useOsprober") eq "true") {
+    system(get("shell"), "-c", "pkgdatadir=$grub/share/grub $grub/etc/grub.d/30_os-prober >> $tmpFile");
+}
+
+# Atomically switch to the new config
 rename $tmpFile, $confFile or die "cannot rename $tmpFile to $confFile\n";