#+TITLE:   lang/haskell
#+DATE:    January 16, 2017
#+SINCE:   v0.7
#+STARTUP: inlineimages

* Table of Contents :TOC:
- [[#description][Description]]
  - [[#maintainers][Maintainers]]
  - [[#module-flags][Module Flags]]
  - [[#plugins][Plugins]]
- [[#prerequisites][Prerequisites]]
- [[#features][Features]]
- [[#configuration][Configuration]]

* Description
Adds Haskell support to Doom Emacs.

** Maintainers
This module has no dedicated maintainers.

** Module Flags
+ =+lsp= Enable LSP support with for [[https://github.com/haskell/haskell-language-server][haskell-language-server]] (requires the =:tools lsp= module).

** Plugins
+ [[https://github.com/haskell/haskell-mode][haskell-mode]]
+ [[https://github.com/emacs-lsp/lsp-haskell][lsp-haskell]] (=+lsp=, =:tools lsp=)

* Prerequisites
It is recommended to install the haskell tooling using [[https://www.haskell.org/ghcup/][ghcup]]. Only ghc is needed
for basic functionality:

#+BEGIN_SRC bash
ghcup install ghc
#+END_SRC

but =+lsp= users should also install the language server:

#+BEGIN_SRC bash
ghcup install hls
#+END_SRC

Installing [[https://www.haskell.org/cabal/][cabal]] or [[https://docs.haskellstack.org/en/stable/README/][stack]] as well is recommended, and can be done through
=ghcup=.

=haskell-mode= provides support for [[https://github.com/ndmitchell/hoogle][hoogle]], which can be installed through
system package manager, cabal, or stack.

=haskell-language-server= provides support for [[https://github.com/ndmitchell/hlint/][hlint]], and haskell code
formatters such as [[https://github.com/lspitzner/brittany][brittany]], [[https://github.com/ennocramer/floskell][floskell]], [[https://github.com/tweag/ormolu][ormolu]], [[https://github.com/fourmolu/fourmolu][fourmolu]], and [[https://github.com/haskell/stylish-haskell][stylish-haskell]],
which can be installed through system package manager, cabal, or stack.

* Features
This module intergrates the haskell packages into Doom by providing things such
as repl support, project root recognition, etc. It also provide the following
keybindings:

| Keybinding        | Description                                   |
|-------------------+-----------------------------------------------|
| =<localleader> b= | Build the current cabal project               |
| =<localleader> c= | Visit the =.cabal= file of the current buffer |
| =<localleader> h= | Toggle visibility of the form at point        |
| =<localleader> H= | hides all top level functions                 |

* Configuration
After installing your preferred formatter, make sure to set
=lsp-haskell-formatting-provider= to it.

Make sure to configure the lsp to use your perfered formatter, e.g.:
#+BEGIN_SRC elisp
;; ~/.doom.d/config.el
(after!
  (setq lsp-haskell-formatting-provider "brittany"))
#+END_SRC