add devShell to flake template snippet

init.lua

@@ -70,6 +70,7 @@ end
 vim.cmd.colorscheme "catppuccin"
 
 function set_theme_according_to_darkman()
+  if vim.fn.executable("darkman") == 1 then
     local obj = vim.system({ 'darkman', 'get' }, { text = true }):wait()
     if obj.code == 0 then
       local theme = "light"
@@ -83,6 +84,7 @@ function set_theme_according_to_darkman()
       opt.background = theme
       vim.api.nvim_exec_autocmds("ColorScheme", {})
     end
+  end
 end
 
 set_theme_according_to_darkman()

snippets/nix.snippets

@@ -33,7 +33,7 @@ snippet flake
         let
           pkgs = nixpkgs.legacyPackages.\${system};
         in
-        {
+        rec {
           packages = rec {
             $1 = pkgs.stdenv.mkDerivation {
               name = "$1";
@@ -43,6 +43,12 @@ snippet flake
             };
             default = $1;
           };
+          devShells.default = {
+            inputsFrom = [ packages.default ];
+            packages = with pkgs; [
+              $3
+            ];
+          };
         }
       );
   }

snippets/python.snippets

@@ -0,0 +1,2 @@
+snippet exception Exception statement
+  Exception(f"$1")