feat: devshell.menu.interpolate option

Author: deemp

modules/commands.nix

@@ -178,7 +178,7 @@ in
       help = "prints this menu";
       name = "menu";
       command = ''
-        cat <<'DEVSHELL_MENU'
+        cat <<${(x: if config.devshell.menu.interpolate then x else "'${x}'") "DEVSHELL_MENU"}
         ${commandsToMenu config.commands}
         DEVSHELL_MENU
       '';

modules/devshell.nix

@@ -345,6 +345,21 @@ in
         options list (except that the 'name' field is ignored).
       '';
     };
+
+    menu = mkOption {
+      type = types.submodule {
+        options.interpolate = mkEnableOption "interpolation in the devshell menu";
+      };
+      default = { };
+      description = ''
+        Controls devshell menu
+      '';
+      example = literalExpression ''
+        {
+          interpolate = true;
+        }
+      '';
+    };
   };
 
   config.devshell = {

tests/extra/devshell.menu.interpolate.nix

@@ -0,0 +1,20 @@
+{ pkgs, devshell, runTest }:
+{
+  interpolate =
+    let
+      shell = devshell.mkShell {
+        devshell.menu.interpolate = true;
+        commands = [
+          { package = "hello"; help = "start at $PRJ_ROOT"; }
+          { package = "jq"; help = ''jq from '\$PRJ_ROOT'!''; }
+        ];
+      };
+    in
+    runTest "interpolate" { } ''
+      # Check interpolation is enabled
+      cat ${shell}/bin/menu | grep '<<DEVSHELL_MENU'
+      
+      # Check escaped variable
+      eval ${shell}/bin/menu | grep '\$PRJ_ROOT'
+    '';
+}