#+TITLE: Nix Options -- A set of useful Emacs modes and functions for users of Nix and Nix OS.

| nixos-options                                     | helm-nixos-options                                     | ivy-nixos-options                                       | company-nixos-options                                     | nix-sandbox                                           |
| [[http://melpa.org/#/nixos-options][http://melpa.org/packages/nixos-options-badge.svg]] | [[http://melpa.org/#/helm-nixos-options][http://melpa.org/packages/helm-nixos-options-badge.svg]] | [[http://melpa.org/packages/ivy-nixos-options-badge.svg]] | [[http://melpa.org/#/company-nixos-options][http://melpa.org/packages/company-nixos-options-badge.svg]] | [[https://melpa.org/#/nix-sandbox][file:https://melpa.org/packages/nix-sandbox-badge.svg]] |


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** Usage

*** helm-nixos-options

The function =helm-nixos-options= is the one that you want to bind. You are free
to choose where and if you want it global you can have this.

#+begin_src emacs-lisp
  (global-set-key (kbd "C-c C-S-n") 'helm-nixos-options)
#+end_src

It looks like this

[[file:img/helm-nixos-options-candidates.png]]

The description of the option is shown in the minibuffer

If you want more information, there is a detailed buffer when you press =return=

[[file:img/helm-nixos-options-doc-buffer.png]]

There are also other actions like inserting the current match into the buffer

[[file:img/helm-nixos-options.gif]]

*** ivy-nixos-options

Use this if you don't want the rather heavy =helm= dependency.
The function =ivy-nixos-options= is the one that you want to bind. You are free
to choose where and if you want it global you can have this.

#+begin_src emacs-lisp
  (global-set-key (kbd "C-c C-S-n") 'ivy-nixos-options)

  (setq ivy-nixos-options-default 1)
  ; defines what function is being called when pressing return. I like to have it set to 2
  ; All of the actions can always be called when pressing M-o
  ; 1 = show the docs buffer (default)
  ; 2 = insert the string
  ; 3 = only show the description of the command
  #+end_src

It looks like this

[[file:img/ivy-nixos-options-candidates.png]]

If you want more information, there is a detailed buffer when you press =return=

[[file:img/ivy-nixos-options-doc-buffer.png]]

There are also other actions like inserting the current match into the buffer.
The builtin help menu from ivy (display with =M-o=) shows all possible options. e.g. =M-o i= will insert the option

[[file:img/ivy-nixos-options-actions.png]]


*** company-nixos-options

Add company-nixos-options to allowed company-mode backends list

#+begin_src emacs-lisp
  (add-to-list 'company-backends 'company-nixos-options)
#+end_src

For now it shows the documentation of the option in a popup-buffer.

[[file:img/company-nixos-options.gif]]

*** nix-sandbox

Utility functions to work with nix sandboxes.

 - ~nix-shell-command~ composes command that can be executed in the given sandbox
 - ~nix-shell~ executes a command in the given sandbox
 - ~nix-compile~ compiles a program in the given sandbox
 - ~nix-find-sandbox~ searches from the given path upwards until it
   finds a =shell.nix= or =default.nix= file.
 - ~nix-current-sandbox~ searches for a sandbox file starting from the current working directory.
 - ~nix-executable-find~ a replacement for the built-in =executable-find=. The function searches in the given sandbox for executables.

**** Flycheck

With this configuration [[http://www.flycheck.org/][flycheck]] can find executables of checkers that would be only accessible via =nix-shell=:

#+begin_src emacs-lisp
(setq flycheck-command-wrapper-function
        (lambda (command) (apply 'nix-shell-command (nix-current-sandbox) command))
      flycheck-executable-find
        (lambda (cmd) (nix-executable-find (nix-current-sandbox) cmd)))
#+end_src

**** Haskell Mode

Add these lines to your configuration to allow [[https://github.com/haskell/haskell-mode][haskell-mode]] to look for =ghc= in the current sandbox.

#+begin_src emacs-lisp
(setq haskell-process-wrapper-function
        (lambda (args) (apply 'nix-shell-command (nix-current-sandbox) args)))
#+end_src