pyrox.dev
1# Emacs {#sec-emacs}
2
3## Configuring Emacs {#sec-emacs-config}
4
5The Emacs package comes with some extra helpers to make it easier to configure. `emacs.pkgs.withPackages` 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 `company` `counsel`, `flycheck`, `ivy`, `magit`, `projectile`, and `use-package` you could use this as a `~/.config/nixpkgs/config.nix` override:
6
7```nix
8{
9 packageOverrides = pkgs: with pkgs; {
10 myEmacs = emacs.pkgs.withPackages (epkgs: (with epkgs.melpaStablePackages; [
11 company
12 counsel
13 flycheck
14 ivy
15 magit
16 projectile
17 use-package
18 ]));
19 };
20}
21```
22
23You can install it like any other packages via `nix-env -iA myEmacs`. However, this will only install those packages. It will not `configure` 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 provides a `default.el` file in `/share/emacs/site-start/`. Emacs knows to load this file automatically when it starts.
24
25```nix
26{
27 packageOverrides = pkgs: with pkgs; rec {
28 myEmacsConfig = writeText "default.el" ''
29 (eval-when-compile
30 (require 'use-package))
31
32 ;; load some packages
33
34 (use-package company
35 :bind ("<C-tab>" . company-complete)
36 :diminish company-mode
37 :commands (company-mode global-company-mode)
38 :defer 1
39 :config
40 (global-company-mode))
41
42 (use-package counsel
43 :commands (counsel-descbinds)
44 :bind (([remap execute-extended-command] . counsel-M-x)
45 ("C-x C-f" . counsel-find-file)
46 ("C-c g" . counsel-git)
47 ("C-c j" . counsel-git-grep)
48 ("C-c k" . counsel-ag)
49 ("C-x l" . counsel-locate)
50 ("M-y" . counsel-yank-pop)))
51
52 (use-package flycheck
53 :defer 2
54 :config (global-flycheck-mode))
55
56 (use-package ivy
57 :defer 1
58 :bind (("C-c C-r" . ivy-resume)
59 ("C-x C-b" . ivy-switch-buffer)
60 :map ivy-minibuffer-map
61 ("C-j" . ivy-call))
62 :diminish ivy-mode
63 :commands ivy-mode
64 :config
65 (ivy-mode 1))
66
67 (use-package magit
68 :defer
69 :if (executable-find "git")
70 :bind (("C-x g" . magit-status)
71 ("C-x G" . magit-dispatch-popup))
72 :init
73 (setq magit-completing-read-function 'ivy-completing-read))
74
75 (use-package projectile
76 :commands projectile-mode
77 :bind-keymap ("C-c p" . projectile-command-map)
78 :defer 5
79 :config
80 (projectile-global-mode))
81 '';
82
83 myEmacs = emacs.pkgs.withPackages (epkgs: (with epkgs.melpaStablePackages; [
84 (runCommand "default.el" {} ''
85 mkdir -p $out/share/emacs/site-lisp
86 cp ${myEmacsConfig} $out/share/emacs/site-lisp/default.el
87 '')
88 company
89 counsel
90 flycheck
91 ivy
92 magit
93 projectile
94 use-package
95 ]));
96 };
97}
98```
99
100This provides a fairly full Emacs start file. It will load in addition to the user's personal config. You can always disable it by passing `-q` to the Emacs command.
101
102Sometimes `emacs.pkgs.withPackages` is not enough, as this package set has some priorities imposed on packages (with the lowest priority assigned to GNU-devel ELPA, and the highest for packages manually defined in `pkgs/applications/editors/emacs/elisp-packages/manual-packages`). But you can't control these priorities when some package is installed as a dependency. You can override it on a 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 `overrideScope`.
103
104```nix
105let
106 overrides = self: super: rec {
107 haskell-mode = self.melpaPackages.haskell-mode;
108 # ...
109 };
110in
111((emacsPackagesFor emacs).overrideScope overrides).withPackages
112 (p: with p; [
113 # here both these package will use haskell-mode of our own choice
114 ghc-mod
115 dante
116 ])
117```
118}