emacs: Configure formatter for nil

home-manager/modules/emacs/config.org

@@ -1371,6 +1371,15 @@ Add [[https://github.com/NixOS/nix-mode][nix-mode]]
     :hook (nix-mode . eglot-ensure))
 #+end_src
 
+Tell =nil= to use =nixpkgs-fmt= for formatting nix files.
+
+#+begin_src emacs-lisp
+  (with-eval-after-load 'eglot
+    (add-to-list 'eglot-server-programs
+                 '(nix-mode . ("nil" :initializationOptions
+                               `(:nil (:formatting (:command ("nixpkgs-fmt"))))))))
+#+end_src
+
 *** Common Lisp
 
 Common Lisp does not use =lsp-mode=, but has it's own environment: [[https://github.com/slime/slime][SLIME]] or Superior Lisp Interaction Mode for Emacs.

home-manager/modules/emacs/default.nix

@@ -79,6 +79,7 @@ in
       nodePackages.bash-language-server
       aspell
       nil
+      nixpkgs-fmt
       python3
       lldb
     ] ++