#+TITLE: NixOS layer

#+TAGS: layer|os

[[file:img/nixos.png]]

* Table of Contents                     :TOC_5_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#install][Install]]
  - [[#layer][Layer]]
- [[#configuration][Configuration]]
  - [[#enabling-lsp-experimental][Enabling LSP (Experimental)]]
  - [[#format-on-save][Format on save]]
  - [[#opt-out-from-auto-complete][Opt-out from =auto-complete=]]
- [[#key-bindings][Key bindings]]
  - [[#nixos-options][NixOS Options]]

* Description
This layer adds tools for better integration of Emacs in NixOS.

** Features:
- Nix-mode using [[https://github.com/NixOS/nix-mode][nix-mode]]
- Automatic formatting via [[https://github.com/serokell/nixfmt][nixfmt]]
- Auto-completion of NixOS Options using [[https://github.com/travisbhartwell/nix-emacs/blob/master/company-nixos-options.el][company-nixos-options]]
- Helm Lookup for NixOS Options [[https://github.com/travisbhartwell/nix-emacs/blob/master/helm-nixos-options.el][helm-nixos-options]]
- WIP support for LSP backend using =rnix-lsp=

* Install
** Layer
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =nixos= to the existing =dotspacemacs-configuration-layers= list in this
file.

* Configuration
** Enabling LSP (Experimental)
To use the /experimental/ LSP backend, set variable =nix-backend= to =lsp= in
your =~./spacemacs=. (You would also need to enable [[file:../../+tools/lsp/README.org][LSP]] layer).

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                (nixos :variables nix-backend 'lsp))
#+END_SRC

To install [[https://github.com/nix-community/rnix-lsp][rnix-lsp]] from =nix=, run the following command in shell:

#+BEGIN_SRC shell
  nix-env -i -f https://github.com/nix-community/rnix-lsp/archive/master.tar.gz
#+END_SRC

** Format on save
To enable automatic formatting on save, set the layer variable
=nixos-format-on-save= to =t=:

#+BEGIN_SRC elisp
  (setq-default dotspacemacs-configuration-layers
                (nixos :variables nixos-format-on-save t))
#+END_SRC

** Opt-out from =auto-complete=
On some systems, =company-nixos-options= may be very slow. If this is the case,
see the section on disabling the [[https://github.com/syl20bnr/spacemacs/blob/develop/doc/DOCUMENTATION.org#disabling-layer-services-in-other-layers][disabling auto-complete]] for the =nixos= layer.

* Key bindings
** NixOS Options

| Key binding | Description                |
|-------------+----------------------------|
| ~SPC h >~   | Call helm-nixos-options    |
| ~SPC m = =~ | Format buffer using nixfmt |