nixos/nano: add enable, package option, do not create /etc/nanorc by default

and remove nano from environment.defaultPackages. In addition also cleanup the file in general.

This is a follow up to #220481

Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>

nixos/doc/manual/release-notes/rl-2311.section.md

@@ -196,6 +196,10 @@
 
 - `spamassassin` no longer supports the `Hashcash` module. The module needs to be removed from the `loadplugin` list if it was copied over from the default `initPreConf` option.
 
+- `nano` was removed from `environment.defaultPackages`. To not leave systems without a editor, now `programs.nano.enable` is enabled by default.
+
+- `programs.nano.nanorc` and `programs.nano.syntaxHighlight` no longer have an effect unless `programs.nano.enable` is set to true which is the default.
+
 - `services.outline.sequelizeArguments` has been removed, as `outline` no longer executes database migrations via the `sequelize` cli.
 
 - The binary of the package `cloud-sql-proxy` has changed from `cloud_sql_proxy` to `cloud-sql-proxy`.

nixos/modules/config/system-path.nix

@@ -42,8 +42,7 @@ let
     ];
 
   defaultPackageNames =
-    [ "nano"
-      "perl"
+    [ "perl"
       "rsync"
       "strace"
     ];

nixos/modules/programs/nano.nix

@@ -2,14 +2,16 @@
 
 let
   cfg = config.programs.nano;
-  LF = "\n";
 in
 
 {
-  ###### interface
-
   options = {
     programs.nano = {
+      enable = lib.mkEnableOption (lib.mdDoc "nano") // {
+        default = true;
+      };
+
+      package = lib.mkPackageOptionMD pkgs "nano" { };
 
       nanorc = lib.mkOption {
         type = lib.types.lines;
@@ -24,28 +26,22 @@ in
           set tabsize 2
         '';
       };
+
       syntaxHighlight = lib.mkOption {
         type = lib.types.bool;
-        default = true;
+        default = false;
         description = lib.mdDoc "Whether to enable syntax highlight for various languages.";
       };
     };
   };
 
-  ###### implementation
-
-  config = lib.mkIf (cfg.nanorc != "" || cfg.syntaxHighlight) {
-    environment.etc.nanorc.text = lib.concatStringsSep LF (
-      ( lib.optionals cfg.syntaxHighlight [
-          "# The line below is added because value of programs.nano.syntaxHighlight is set to true"
-          ''include "${pkgs.nano}/share/nano/*.nanorc"''
-          ""
-      ])
-      ++ ( lib.optionals (cfg.nanorc != "") [
-        "# The lines below have been set from value of programs.nano.nanorc"
-        cfg.nanorc
-      ])
-    );
+  config = lib.mkIf cfg.enable {
+    environment = {
+      etc.nanorc.text = (lib.optionalString cfg.syntaxHighlight ''
+        # load syntax highlighting files
+        include "${cfg.package}/share/nano/*.nanorc"
+      '') + cfg.nanorc;
+      systemPackages = [ cfg.package ];
+    };
   };
-
 }