working home manager switch without --impure

modules/home-manager/shell.nix

@@ -1,42 +1,19 @@
-{ inputs, ... }:
+{ inputs, lib, ... }:
 {
-  flake.homeModules.shell = {pkgs, lib, ...}:
+  flake.homeModules.shell = { config, ... }:
   {
-    imports = with inputs.self.homeModules; [
-      # Shells
-      # bash
-      zsh
-      
-      # Tools
-      shell-tools
-      files
-      docker
-    ];
-
-    programs.eza = {
-      enable = true;
-      package = pkgs.eza;
-      enableBashIntegration = true;
-      enableZshIntegration = true;
+    options.shell.program = lib.mkOption {
+      type = lib.types.enum [ "bash" "zsh" ];
+      default = "zsh";
+      description = "Which interactive shell configuration to enable.";
     };
 
-    home.shell.enableShellIntegration = true;
-    home.shellAliases = {
-      ls = "${lib.getExe pkgs.eza} -lgos type --no-time --follow-symlinks";
-    };
-  };
+    imports = with inputs.self.homeModules; [ bash zsh ];
 
-  flake.homeModules.shell-tools = {pkgs, ...}: {
-    home.packages = with pkgs; [
-      wget
-      curl
-      cacert
-      busybox
-      gnugrep
-      dig
-      btop
-      uv
-      xclip
-    ];
+    config = {
+      programs.bash.enable = lib.mkForce (config.shell.program == "bash");
+      programs.zsh.enable  = lib.mkForce (config.shell.program == "zsh");
+      home.shell.enableShellIntegration = true;
+    };
   };
 }