Allow formatting partitions in the script

lib/modules/partition.nix

@@ -5,6 +5,12 @@
     diskVar = ''''${${diskVarName}}'';
     isSwap = partition: builtins.elem partition.type ["swap" 19];
 
+    fs = {
+      ext4 = "ext4";
+      ntfs = "ntfs";
+      fat32 = "fat32";
+    };
+
     diskSelector = ''
       . ${./../../scripts/Common/Scripts/choose-disk.sh};
       chooseDisk ${diskVarName} "Which disk do you wish to install the OS on?";
@@ -79,6 +85,7 @@
               partition:
                 let
                   inherit (partition)
+                    format
                     index
                     keepExisting
                     sizeScript
@@ -89,9 +96,19 @@
                     ${sizeScript} | sed -e "s/.*[^[:space:]]/size=\0/"
                   '';
 
-                  create = appendScript "${toString index}: \"$(${sizeOption})\" type=${lib.strings.escapeShellArg type}";
+                  formatScripts = {
+                    ${fs.ext4} = "mkfs.ext4 -F ${diskVar}";
+                    ${fs.ntfs} = "mkfs.ntfs -F ${diskVar}";
+                    ${fs.fat32} = "mkfs.fat -F 32 ${diskVar}";
+                  };
+
+                  create = lib.strings.concatLines [
+                    (appendScript "${toString index}: \"$(${sizeOption})\" type=${lib.strings.escapeShellArg type}")
+                    formatScripts.${format}
+                  ];
+
                   fallback = ''
-                    if ! { ls "${diskVar}"?(p)${toString partition.index} 2>&1; } > /dev/null
+                    if ! { ls "${diskVar}"?(p)${toString index} 2>&1; } > /dev/null
                     then
                       ${create}
                     fi
@@ -161,6 +178,11 @@
             default = null;
           };
 
+          format = mkOption {
+            type = types.enum (builtins.attrValues fs);
+            description = "The file system format of the partition.";
+          };
+
           size = mkOption {
             type = types.nullOr types.str;
             description = "The size of the partition.";
@@ -215,17 +237,19 @@
               index = 1;
               type = "uefi";
               size = "+1G";
+              format = fs.fat32;
             };
 
             Swap = {
               index = 2;
               type = "swap";
+              format = fs.ntfs;
             };
 
             OS = {
               index = 3;
               type = "linux";
-              size = "";
+              format = fs.ext4;
             };
           };
         };