refactor: make fish overrideable using mkdefault

flake.nix

@@ -30,7 +30,7 @@
         specialArgs = { inherit inputs; };
         system = "x86_64-linux";
         modules = [
-          ./configuration.nix
+          ./modules/nixos/nixos-configuration.nix
           ./modules/nixos/secureboot.nix
           ./modules/nixos/gaming.nix
           ./modules/nixos/audio.nix

modules/darwin/darwin-configuration.nix

@@ -0,0 +1,39 @@
+{ config, pkgs, ... }: {
+  # List packages installed in system profile. To search by name, run:
+  # $ nix-env -qaP | grep wget
+  environment.systemPackages = with pkgs; [ ];
+
+  # Use a custom configuration.nix location.
+  # $ darwin-rebuild switch -I darwin-config=$HOME/.config/nixpkgs/darwin/configuration.nix
+  # environment.darwinConfig = "$HOME/.config/nixpkgs/darwin/configuration.nix";
+
+  # Auto upgrade nix package and the daemon service.
+  services.nix-daemon.enable = true;
+  # nix.package = pkgs.nix;
+
+  nix.settings.experimental-features = "nix-command flakes";
+
+  nixpkgs.config.allowUnfree = true;
+
+  # Create /etc/zshrc that loads the nix-darwin environment.
+  programs.zsh.enable = true; # default shell on catalina
+  programs.fish.enable = true;
+  programs.bash.enable = true;
+
+  system.configurationRevision =
+    config.self.rev or config.self.dirtyRev or null;
+
+  nixpkgs.hostPlatform = "aarch64-darwin";
+
+  # Used for backwards compatibility, please read the changelog before changing.
+  # $ darwin-rebuild changelog
+  system.stateVersion = 4;
+
+  users.users.youwen = {
+    home = "/Users/youwen";
+    description = "Youwen Wu";
+    shell = pkgs.fish;
+  };
+
+  security.pam.enableSudoTouchIdAuth = true;
+}

modules/home-manager/common/core.nix

@@ -73,7 +73,7 @@
     useTheme = "gruvbox";
   };
 
-  programs.fish = {
+  programs.fish = pkgs.lib.mkDefault {
     enable = true;
     catppuccin.enable = true;
     catppuccin.flavor = "mocha";