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<section xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xml:id="sec-emacs">
<title>Emacs</title>
<section xml:id="sec-emacs-config">
<title>Configuring Emacs</title>
<para>
The Emacs package comes with some extra helpers to make it easier to configure. <varname>emacsWithPackages</varname> allows you to manage packages from ELPA. This means that you will not have to install that packages from within Emacs. For instance, if you wanted to use <literal>company</literal>, <literal>counsel</literal>, <literal>flycheck</literal>, <literal>ivy</literal>, <literal>magit</literal>, <literal>projectile</literal>, and <literal>use-package</literal> you could use this as a <filename>~/.config/nixpkgs/config.nix</filename> override:
</para>
<screen>
{
packageOverrides = pkgs: with pkgs; {
myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
company
counsel
flycheck
ivy
magit
projectile
use-package
]));
}
}
</screen>
<para>
You can install it like any other packages via <command>nix-env -iA myEmacs</command>. However, this will only install those packages. It will not <literal>configure</literal> them for us. To do this, we need to provide a configuration file. Luckily, it is possible to do this from within Nix! By modifying the above example, we can make Emacs load a custom config file. The key is to create a package that provide a <filename>default.el</filename> file in <filename>/share/emacs/site-start/</filename>. Emacs knows to load this file automatically when it starts.
</para>
<screen>
{
packageOverrides = pkgs: with pkgs; rec {
myEmacsConfig = writeText "default.el" ''
;; initialize package
(require 'package)
(package-initialize 'noactivate)
(eval-when-compile
(require 'use-package))
;; load some packages
(use-package company
:bind ("<C-tab>" . company-complete)
:diminish company-mode
:commands (company-mode global-company-mode)
:defer 1
:config
(global-company-mode))
(use-package counsel
:commands (counsel-descbinds)
:bind (([remap execute-extended-command] . counsel-M-x)
("C-x C-f" . counsel-find-file)
("C-c g" . counsel-git)
("C-c j" . counsel-git-grep)
("C-c k" . counsel-ag)
("C-x l" . counsel-locate)
("M-y" . counsel-yank-pop)))
(use-package flycheck
:defer 2
:config (global-flycheck-mode))
(use-package ivy
:defer 1
:bind (("C-c C-r" . ivy-resume)
("C-x C-b" . ivy-switch-buffer)
:map ivy-minibuffer-map
("C-j" . ivy-call))
:diminish ivy-mode
:commands ivy-mode
:config
(ivy-mode 1))
(use-package magit
:defer
:if (executable-find "git")
:bind (("C-x g" . magit-status)
("C-x G" . magit-dispatch-popup))
:init
(setq magit-completing-read-function 'ivy-completing-read))
(use-package projectile
:commands projectile-mode
:bind-keymap ("C-c p" . projectile-command-map)
:defer 5
:config
(projectile-global-mode))
'';
myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
(runCommand "default.el" {} ''
mkdir -p $out/share/emacs/site-lisp
cp ${myEmacsConfig} $out/share/emacs/site-lisp/default.el
'')
company
counsel
flycheck
ivy
magit
projectile
use-package
]));
};
}
</screen>
<para>
This provides a fairly full Emacs start file. It will load in addition to the user's presonal config. You can always disable it by passing <command>-q</command> to the Emacs command.
</para>
<para>
Sometimes <varname>emacsWithPackages</varname> is not enough, as this package set has some priorities imposed on packages (with the lowest priority assigned to Melpa Unstable, and the highest for packages manually defined in <filename>pkgs/top-level/emacs-packages.nix</filename>). But you can't control this priorities when some package is installed as a dependency. You can override it on per-package-basis, providing all the required dependencies manually - but it's tedious and there is always a possibility that an unwanted dependency will sneak in through some other package. To completely override such a package you can use <varname>overrideScope'</varname>.
</para>
<screen>
overrides = self: super: rec {
haskell-mode = self.melpaPackages.haskell-mode;
...
};
((emacsPackagesGen emacs).overrideScope' overrides).emacsWithPackages (p: with p; [
# here both these package will use haskell-mode of our own choice
ghc-mod
dante
])
</screen>
</section>
</section>
|
