132 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			XML
		
	
	
	
	
	
			
		
		
	
	
			132 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			XML
		
	
	
	
	
	
<section xmlns="http://docbook.org/ns/docbook"
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         xmlns:xlink="http://www.w3.org/1999/xlink"
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         xml:id="sec-emacs">
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 <title>Emacs</title>
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 <section xml:id="sec-emacs-config">
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  <title>Configuring Emacs</title>
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  <para>
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   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:
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  </para>
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<screen>
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{
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  packageOverrides = pkgs: with pkgs; {
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    myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
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      company
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      counsel
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      flycheck
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      ivy
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      magit
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      projectile
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      use-package
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    ]));
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  }
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}
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</screen>
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  <para>
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   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.
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  </para>
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<screen>
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{
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  packageOverrides = pkgs: with pkgs; rec {
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    myEmacsConfig = writeText "default.el" ''
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;; initialize package
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(require 'package)
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(package-initialize 'noactivate)
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(eval-when-compile
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  (require 'use-package))
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;; load some packages
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(use-package company
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  :bind ("<C-tab>" . company-complete)
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  :diminish company-mode
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  :commands (company-mode global-company-mode)
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  :defer 1
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  :config
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  (global-company-mode))
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(use-package counsel
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  :commands (counsel-descbinds)
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  :bind (([remap execute-extended-command] . counsel-M-x)
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         ("C-x C-f" . counsel-find-file)
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         ("C-c g" . counsel-git)
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         ("C-c j" . counsel-git-grep)
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         ("C-c k" . counsel-ag)
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         ("C-x l" . counsel-locate)
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         ("M-y" . counsel-yank-pop)))
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(use-package flycheck
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  :defer 2
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  :config (global-flycheck-mode))
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(use-package ivy
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  :defer 1
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  :bind (("C-c C-r" . ivy-resume)
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         ("C-x C-b" . ivy-switch-buffer)
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         :map ivy-minibuffer-map
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         ("C-j" . ivy-call))
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  :diminish ivy-mode
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  :commands ivy-mode
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  :config
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  (ivy-mode 1))
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(use-package magit
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  :defer
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  :if (executable-find "git")
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  :bind (("C-x g" . magit-status)
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         ("C-x G" . magit-dispatch-popup))
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  :init
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  (setq magit-completing-read-function 'ivy-completing-read))
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(use-package projectile
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  :commands projectile-mode
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  :bind-keymap ("C-c p" . projectile-command-map)
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  :defer 5
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  :config
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  (projectile-global-mode))
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    '';
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    myEmacs = emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [
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      (runCommand "default.el" {} ''
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mkdir -p $out/share/emacs/site-lisp
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cp ${myEmacsConfig} $out/share/emacs/site-lisp/default.el
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'')
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      company
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      counsel
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      flycheck
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      ivy
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      magit
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      projectile
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      use-package
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    ]));
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  };
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}
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</screen>
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  <para>
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   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.
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  </para>
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  <para>
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   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>.
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  </para>
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<screen>
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overrides = self: super: rec {
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  haskell-mode = self.melpaPackages.haskell-mode;
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  ...
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};
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((emacsPackagesGen emacs).overrideScope' overrides).emacsWithPackages (p: with p; [
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  # here both these package will use haskell-mode of our own choice
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  ghc-mod
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  dante
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])
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</screen>
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 </section>
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</section>
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