# hakyll-nix-template

[Hakyll](https://jaspervdj.be/hakyll/) + [Nix](https://nixos.org) template

[![built with nix](https://builtwithnix.org/badge.svg)](https://builtwithnix.org)

## Features

### nix flakes

* Build your site into the `./result/dist` folder:
  ```sh
  λ nix build
  ```
* Start hakyll's dev server that reloads when changes are made:
  ```sh
  λ nix run . watch
  Listening on http://127.0.0.1:8000
  ...more logs
  ```
* Run any hakyll command through `nix run .`!
  ```sh
  λ nix run . clean
  Removing dist...
  Removing ssg/_cache...
  Removing ssg/_tmp...
  ```
* Start a development environment that
  * has your shell environment
  * has `hakyll-site` (for building/watching/cleaning hakyll projects)
  * has `hakyll-init` (for generating new projects)
  * can have anything else you put in the `buildInputs` of the `devShell` in
    `flake.nix`; for example: `haskell-language-server`, `hlint`, and `ormolu`
  * is set up to run `ghci` with some defaults and the modules loaded so you can
    make your own changes and test them out in the ghci REPL

  ```sh
  λ nix develop

  [hakyll]λ hakyll-site build
  ...
  Success

  [hakyll]λ ghci
  ...
  [1 of 1] Compiling Main    ( ssg/src/Main.hs, interpreted )
  ...
  
  λ >
  ```
* Easily unbreak hakyll's nixpkgs distribution or change hakyll's compile flags
via the `./haskell-overlay.nix` and `hakyll.patch` files

### hakyll

All of this is custmomizable, and here are some things that are already done for
you:

* [pandoc](https://github.com/jgm/pandoc/) markdown customization to make it as
  close to GitHub's markdown style as possible
* [`slugger`](https://hackage.haskell.org/package/slugger) module is included that makes nice link URIs based on post titles
* RSS & Atom XML feed generation
* Sitemap generation
* Code syntax highlighting customization
* ...other reasonable defaults

Configure the dev server, cache & tmp directories, and more in
`./ssg/src/Main.hs`.

### Deployment

Deployment is set up through a [GitHub
Action](https://github.com/features/actions) with [cachix](https://cachix.org),
and it deploys to a [GitHub Pages](https://pages.github.com/) branch,
`gh-pages`, when you merge code into your main branch.

Setup information can be found below in the "Cachix" section.

Note: If your main branch's name isn't `main`, ensure `'refs/heads/main'` gets
updated to `'refs/heads/my-main-branch'` in `./github/workflows/main.yml`.

## Setup

### Nix Flakes

If you don't have [nix](https://nixos.org) _and are not running macOS_, follow
[the nix installation instructions](https://nixos.org/download.html).

At the time of writing, the macOS installation is in a weird place. You should
use this:

```sh
λ sh <(curl https://abathur-nix-install-tests.cachix.org/serve/yihf8zbs0jwph2rs9qfh80dnilijxdi2/install) --tarball-url-prefix https://abathur-nix-install-tests.cachix.org/serve
```

Once you have nix installed, follow the instructions here to get access to
flakes: https://nixos.wiki/wiki/Flakes.

### Cachix

The `./.github/workflows/main.yml` file builds with help from
[cachix](https://app.cachix.org), so you'll to generate a signing key to be able
to do this.

1. Create a cache on cachix for your project
1. Follow cachix's instructions to generate a signing keypair
1. Copy the signing keypair value to a new `CACHIX_SIGNING_KEY` secret on
   https://github.com/settings/secrets

## Enable Content-Addressible Derivation (experimental)

Given you have your nix conf `experimental-features` set to something like

```
experimental-features = "nix-command flakes ca-derivations ca-references"
```

Uncomment the `__contentAddressed = true;` line in `haskell-ovelray.nix`, and
then run

```sh
λ nix build --experimental-features "ca-derivations flakes nix-command"
```

## Alternatives to the haskell overlay

### Overriding `legacyPackages`' haskell compiler packages

```nix
pkgs = nixpkgs.legacyPackages.${system};
myHaskellPackages = pkgs.haskell.packages.${haskellCompiler}.override {
  overrides = hpFinal: hpPrev:
    let
      hakyll-src = hpPrev.callHackage "hakyll" "4.14.0.0" {};
      pandoc-src = hpPrev.callHackage "pandoc" "2.11.4" {};
    in {
      hakyll = pipe hakyll-src [
        doJailbreak
        dontCheck
        (withPatch ./hakyll.patch)
        (withFlags [ "-f" "watchServer" "-f" "previewServer" ])
      ];

      pandoc = pipe pandoc-src [
        doJailbreak
        dontCheck
      ];
    };
};
```

## Pulling `hakyll-src` from GitHub

`hakyll-src`, used in the `haskell-overlay.nix` and in the prior example,
doesn't have to come from hackage; it could come from what your pinned nixpkgs
version has via `hakyll-src = hpPrev.hakyll`, or it could come from the hakyll
repo pinned as a nix flake input:

```nix
hakyll-src = {
  url = "github:jaspervdj/hakyll/v4.14.0.0";
  flake = false;
};
```

...and then:

```nix
hakyll-src = hpPrev.callCabal2nix "hakyll" hakyll-src {};
```