Add NixOS Layer

contrib/nixos/README.org

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+#+TITLE: NixOS contribution layer for Spacemacs
+
+[[file:img/nixos.jpg]]
+
+* Table of Contents                                                   :TOC@4:
+ - [[#description][Description]]
+     - [[#features][Features:]]
+ - [[#install][Install]]
+     - [[#layer][Layer]]
+ - [[#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/blob/master/misc/emacs/nix-mode.el][nix-mode]]
+- 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]]
+
+* Install
+
+** Layer
+To use this contribution add it to your =~/.spacemacs=
+
+#+BEGIN_SRC emacs-lisp
+  (setq-default dotspacemacs-configuration-layers '(nixos))
+#+END_SRC
+
+* Key Bindings
+
+** NixOS Options
+
+| Key Binding | Description             |
+|-------------+-------------------------|
+| ~SPC h >~   | Call helm-nixos-options |

contrib/nixos/config.el

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+(spacemacs|defvar-company-backends nix-mode)

contrib/nixos/packages.el

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+(setq nixos-packages '(nix-mode
+                       company
+                       nixos-options
+                       helm-nixos-options
+                       company-nixos-options))
+
+(defun nixos/init-nix-mode ()
+  (use-package nix-mode))
+
+(defun nixos/init-nixos-options ()
+  (use-package nixos-options))
+
+(defun nixos/init-helm-nixos-options ()
+  (use-package helm-nixos-options
+    :config
+    (evil-leader/set-key
+      "h>" 'helm-nixos-options)))
+
+(when (configuration-layer/layer-usedp 'auto-completion)
+  (defun nixos/post-init-company ()
+    (spacemacs|add-company-hook nix-mode)
+    (push 'company-capf company-backends-nix-mode))
+
+  (defun nixos/init-company-nixos-options ()
+    (use-package company-nixos-options
+      :if (configuration-layer/package-usedp 'company)
+      :defer t
+      :init
+      (push 'company-nixos-options company-backends-nix-mode))))