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diff --git a/users/wpcarro/website/blog/content/english/lets-learn-nix-dotfiles.md b/users/wpcarro/website/blog/content/english/lets-learn-nix-dotfiles.md deleted file mode 100644 index 084fb19e44..0000000000 --- a/users/wpcarro/website/blog/content/english/lets-learn-nix-dotfiles.md +++ /dev/null @@ -1,401 +0,0 @@ ---- -title: "Let's Learn Nix: Dotfiles" -date: 2020-03-13T22:23:02Z -draft: true ---- - -## Let's Learn Nix: Dotfiles - -### Dependencies - -Speaking of dependencies, here's what you should know before reading this tutorial. - -- Basic Nix syntax: Nix 1p - -What version of Nix are we using? What version of `<nixpkgs>` are we using? What -operating system are we using? So many variables... - -Cartesian product of all possibilities... - -TODO(wpcarro): Create a graphic of the options. - -### The problems of dotfiles - -How do you manage your dependencies? - -You can use `stow` to install the dotfiles. - -### home-manager - -What we are going to write is most likely less preferable to the following -alternatives: -- using Nix home-manager -- committing your `.gitconfig` into your - -In the next tutorial, we will use [home-manager][wtf-home-mgr] to replace the -functionality that we wrote. - -So why bother completing this? - -### Let's begin - -Welcome to the first tutorial in the [Let's Learn Nix][wtf-lln] series. Today we -are going to create a Nix derivation for one of your dotfiles. - -"Dotfiles" refers to a user's collection of configuration files. Typically these -files look like: -- `.vimrc` -- `.xsessionrc` -- `.bashrc` - -The leading "dot" at the beginning gives dotfiles their name. - -You probably have amassed a collection of dotfiles whether or not you are -aware. For example, if you use [git][wtf-git], the file `~/.gitconfig` should -exist on your machine. You can verify this with: - -```shell -$ stat ~/.gitconfig -``` - -When I was first learning `git`, I learned to configure it using commands I -found in books and tutorials that often looked like: - -```shell -$ git config user.email -``` - -The `~/.gitconfig` file on your machine may look something like this: - -```.gitconfig -[user] - name = John Cleese - email = john@flying-circus.com - username = jcleese -[core] - editor = emacs -[web] - browser = google-chrome -[rerere] - enabled = 1 - autoupdate = 1 -[push] - default = matching -[color] - ui = auto -[alias] - a = add --all - ai = add -i - b = branch - cl = clone - cp = cherry-pick - d = diff - fo = fetch origin - lg = log --oneline --graph --decorate - ps = push - pb = pull --rebase - s = status -``` - -As I ran increasingly more `git config` commands to configure my `git` -preferences, the size of my `.gitconfig` increased, and the less likely I was to -remember which options I set to which values. - -Thankfully a coworker at the time, Ryan ([@rschmukler][who-ryan]), told me that -he version-controlled his `.gitconfig` file along with his other configuration -files (e.g. `.vimrc`) in a repository he called "dotfiles". - -Version-controlling your dotfiles improves upon a workflow where you have a -variety of configuration files scattered around your machine. - -If you look at the above `.gitconfig`, can you spot the dependencies? - -We explicitly depend `emacs` and `google-chrome`. We also *implicitly* depend on -`git`: there is not much value of having a `.gitconfig` file if you also do not -have `git` installed on your machine. - -Dependencies: -- `emacs` -- `google-chrome` - -Let's use Nix to generate this `.gitconfig` file. Here is what I would like our -API to be: - -Let's create a file `gitconfig.nix` and build our function section-by-section: - -TODO(wpcarro): Link to sections here -- options.user -- options.core -- options.web -- options.rerere -- options.push -- options.color -- options.alias - -```shell -$ touch gitconfig.nix -``` - -### options.user - -```haskell -AttrSet -> String -``` - -```nix -user = { - name = "John Cleese"; - email = "john@flying-circus.com"; - username = "jcleese"; -}; -``` - -```.gitconfig -[user] - name = John Cleese - email = john@flying-circus.com - username = jcleese -``` - -### options.core - -```nix -core = { - editor = "${pkgs.emacs}/bin/emacs"; -}; -``` - -```.gitconfig -[core] - editor = /nix/store/<hash>-emacs-<version>/bin/emacs -``` - -### options.web - -```nix -web.browser = "${pkgs.google-chrome}/bin/google-chrome"; -``` - -```.gitconfig -[web] - browser = /nix/store/<hash>-google-chrome-<version>/bin/google-chrome -``` - -### options.rerere - -```nix -rerere = { - enabled = true; - autoupdate = true; -}; -``` - -```.gitconfig -[rerere] - enabled = 1 - autoupdate = 1 -``` - -### options.push - -```nix -push.default = "matching"; -``` - -```.gitconfig -[push] - default = matching -``` - -### options.color - -```nix -color.ui = "auto"; -``` - -```.gitconfig -[color] - ui = auto -``` - -We need to define a function named `gitconfig` that creates a Nix [derivation][wtf-derivation]: - -```nix -# file: gitconfig.nix -let - # Import the <nixpkgs> package repository. - pkgs = import <nixpkgs> {}; - - # Stringify the attribute set, `xs`, as a multilined string formatted as "<key> = <value>". - # See attrsets.nix for more functions that work with attribute sets. - encodeAttrSet = xs: lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k} = ${v}") xs); - - # Define out function name `gitconfig` that accepts an `options` argument. - gitconfig = options: pkgs.stdenv.mkDerivation { - # The gitconfig file that Nix builds will be located /nix/store/some-hash-gitconfig. - name = "gitconfig"; - src = pkgs.writeTextFile ".gitconfig" '' - [user] - name = ${options.user.name} - email = ${options.user.email} - username = ${options.user.username} - [core] - editor = ${options.core.editor} - [web] - editor = ${options.web.browser} - [rerere] - enabled = ${if options.rerere.enabled "1" else "0"} - autoupdate = ${if options.rerere.autoupdate "1" else "0"} - [push] - default = ${options.push.default} - [color] - ui = ${options.color.ui} - [alias] - ${encodeAttrSet options.aliases} - ''; - buildPhase = '' - ${pkgs.coreutils}/bin/cp $src $out - ''; - installPhase = '' - ${pkgs.coreutils}/bin/ln -s $out ~/.gitconfig - ''; - }; -} in gitconfig { - user = { - name = "John Cleese"; - email = "john@flying-circus.com"; - username = "jcleese"; - }; - core = { - editor = "${pkgs.emacs}/bin/emacs"; - }; - web.browser = "${pkgs.google-chrome}/bin/google-chrome"; - rerere = { - enabled = true; - autoupdate = true; - }; - push.default = "matching"; - color.ui = "auto"; - aliases = { - a = "add --all"; - ai = "add -i"; - b = "branch"; - cl = "clone"; - cp = "cherry-pick"; - d = "diff"; - fo = "fetch origin"; - lg = "log --oneline --graph --decorate"; - ps = "push"; - pb = "pull --rebase"; - s = "status"; - }; -} -``` - -### options.alias - -We want to write a function that accepts an attribute set and returns a -string. While Nix is a dynamically typed programming language, thinking in types -helps me clarify what I'm trying to write. - -```haskell -encodeAttrSet :: AttrSet -> String -``` - -I prefer using a Haskell-inspired syntax for describing type signatures. Even if -you haven't written Haskell before, you may find the syntax intuitive. - -Here is a non comprehensive, but demonstrative list of example type signatures: -- `[String]`: A list of strings (i.e. `[ "cogito" "ergo" "sum" ]`) -- `AttrSet`: A nix attribute set (i.e. `{ name = "John Cleese"; age = 80; }`). -- `add :: Integer -> Integer -> Integer`: A function named `add` that accepts - two integers and returns an integer. - -Specifically, we want to make sure that when we call: - -```nix -encodeAttrSet { - a = "add --all"; - b = "branch"; -} -``` - -...it returns a string that looks like this: - -```.gitconfig -a = "add --all" -b = "branch" -``` - - -TODO(wpcarro): @tazjin's nix-1p mentions this. Link to it. -Nix has useful functions scattered all over the place: -- `lib.nix` -- `list.nix` -- `lib.attrSet` - -But I cannot recall exactly which functions we will need to write -`encodeAttrSet`. In these cases, I do the following: -1. Run `nix repl`. -2. Browse the Nix source code. - -Google "nix attribute sets" and find the Github link to `attrsets.nix`. - -You should consider repeating this search but instead of searching for -"attribute sets" search for "lists" and "strings". That is how I found the -functions needed to write `encodeAttrSet`. Let's return to our `nix repl`. - -Load the nixpkgs set: - -```nix -nix-repl> :l <nixpkgs> -Added 11484 variables. -``` - -Define a test input called `attrs`: - -```nix -nix-repl> attrs = { fname = "John"; lname = "Cleese"; } -``` - -Map the attribute set into `[String]` using `lib.mapAttrsToList`: - -```nix -nix-repl> lib.mapAttrsToList (k: v: "${k} = ${toString v}") attrs -[ "fname = John" "lname = Cleese" ] -``` - -Now join the `[String]` together using `lib.concatStringsSep`: - -```nix -nix-repl> lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k} = ${v}") attrs) -"fname = John\nlname = Cleese" -``` - -Now let's use this to define our function `encodeAttrSet`: - -```nix -# file: gitconfig.nix -encodeAttrSet = xs: lib.concatStringsSep "\n" (lib.mapAttrsToList (k: v: "${k} = ${v}") xs); -``` - -### Using nixpkgs search - -[Nixpkgs search][wtf-nixpkgs-search]. - -### Conclusion - -We learned how to help ourselves. - -- Where does `emacs` exist? What about `google-chrome`? [nixpkgs search][wtf-nixpkgs-search] -- Verify that I have it? [nix REPL][using-nix-repl] - -We used Nix to create our first derivation. - -[wtf-lln]: /lets-learn-nix -[wtf-git]: https://git-scm.com/ -[wtf-derivation]: https://nixos.org/nixos/nix-pills/our-first-derivation.html -[wtf-nixpkgs-search]: https://nixos.org/nixos/packages.html?channel=nixos-19.09 -[using-nix-repl]: /using-the-nix-repl -[wtf-home-mgr]: https://github.com/rycee/home-manager -[who-ryan]: https://twitter.com/rschmukler |