Syntax Highlighting and Indentation for Haskell and Cabal with Unicode Support

Vim/Neovim plugin for Haskell language support (including Cabal) which provides better experience than builtin Haskell support in Vim. This plugin also provides support for UnicodeSyntax Haskell language extension (see Unicode-symbols in HaskellWiki).

This is a fork of haskell-vim with added Unicode support. There is no promise though it will always be as the original plugin but only with Unicode support. This fork may have other differences from its origin. The original plugin itself was also forked from idris-vim.

Features

• Covers a broader spectrum of keywords
• Highlighting for new features like type families, pattern synonyms, arrow syntax, recursive do, role annotations, QuasiQuotation
• More contextual highlighting (e.g. highlight as or family only in appropriate places)
• Smarter indentation
• Better Cabal support

Installation

Nix or NixOS

If you are using [Nix or NixOS][] you can look at this page to figure out how to configure your Vim or Neovim including how to add/install the plugins: https://nixos.wiki/wiki/Vim

If you can’t find this haskell-with-unicode.vim plugin in your nixpkgs pin (in pkgs.vimPlugins.* namespace) here are a couple of examples how you can configure it in your configuration.nix.

As programs.vim in case of NixOS:

{ pkgs, ... }:
let
  haskell-with-unicode = vimUtils.buildVimPlugin rec {
    pname = "haskell-with-unicode.vim";
    name = pname;
    src = fetchTarball {
      # Replace `fff` with your commit hash
      url = "https://github.com/wenzel-hoffman/haskell-with-unicode.vim/archive/fff.tar.gz";
      # To get a checksum try to rebuild the configuration once and take the hash
      # from the error log or call (the URL from above, remember to replace `fff`):
      #   nix-prefetch-url --unpack https://github.com/wenzel-hoffman/haskell-with-unicode.vim/archive/fff.tar.gz
      sha256 = "0000000000000000000000000000000000000000000000000000";
    };
  };
in
{
  programs.vim = {
    enable = true;
    plugins = [ haskell-with-unicode ];
    extraConfig = ''
      syntax on
      filetype plugin indent on
    '';
  };
}

Or as a regular derivation (this can be used just with Nix, outside of NixOS). Just create default.nix with the below contents:

{ pkgs ? import <nixpkgs> {} }:
let
  haskell-with-unicode = pkgs.vimUtils.buildVimPlugin rec {
    pname = "haskell-with-unicode.vim";
    name = pname;
    src = fetchTarball {
      # Replace `fff` with your commit hash
      url = "https://github.com/wenzel-hoffman/haskell-with-unicode.vim/archive/fff.tar.gz";
      # To get a checksum try to rebuild the configuration once and take the hash
      # from the error log or call (the URL from above, remember to replace `fff`):
      #   nix-prefetch-url --unpack https://github.com/wenzel-hoffman/haskell-with-unicode.vim/archive/fff.tar.gz
      sha256 = "0000000000000000000000000000000000000000000000000000";
    };
  };

  vimWithPlugins = pkgs.vim_configurable.customize {
    vimrcConfig = {
      packages.myPlugins.start = [ haskell-with-unicode ];
      customRC = ''
        syntax on
        filetype plugin indent on
      '';
    };
  };
in
pkgs.mkShell {
  buildInputs = [ vimWithPlugins ];
}

And run (being in the directory where you created that default.nix file):

nix-shell --run 'vim hello.hs'

P.S. You can use Niv (written in Haskell) for easier management of the plugin updates.

VimPlug

Add this line into your .vimrc (Vim) or init.vim (Neovim):

Plug 'wenzel-hoffman/haskell-with-unicode.vim'

Restart Vim/Neovim and execute :PlugInstall

Pathogen

N.B. For Neovim just replace ~/.vim to ~/.config/nvim

Clone this repo into your ~/.vim/bundle directory and you are ready to go.

cd ~/.vim/bundle
git clone https://github.com/wenzel-hoffman/haskell-with-unicode.vim.git

Manual Installation

Copy content into your ~/.vim (Vim) or ~/.config/nvim (Neovim) directory.

Configuration

Features

To enable the features you would like to use, just add the according line to your .vimrc (Vim) or init.vim (Neovim).

let g:haskell_enable_quantification = 1   " to enable highlighting of `forall`
let g:haskell_enable_recursivedo = 1      " to enable highlighting of `mdo` and `rec`
let g:haskell_enable_arrowsyntax = 1      " to enable highlighting of `proc`
let g:haskell_enable_pattern_synonyms = 1 " to enable highlighting of `pattern`
let g:haskell_enable_typeroles = 1        " to enable highlighting of type roles
let g:haskell_enable_static_pointers = 1  " to enable highlighting of `static`
let g:haskell_backpack = 1                " to enable highlighting of backpack keywords

Highlighting

This plugin has an opinionated highlighting. If you do not like that you can switch to a more traditional mode by setting g:haskell_classic_highlighting to 1.

Disabling Template Haskell and QuasiQuoting syntax is possible by setting g:haskell_disable_TH to 1.

Indentation

If you dislike how indentation works you can disable it by setting g:haskell_indent_disable to 1.

To configure indentation you can use the following variables to change indentation depth, just add the according line to your .vimrc (Vim) or init.vim (Neovim).

Haskell

• let g:haskell_indent_if = 3

  if bool
  >>>then ...
  >>>else ...

• let g:haskell_indent_case = 2

  case xs of
  >>[]     -> ...
  >>(y:ys) -> ...

• let g:haskell_indent_let = 4

  let x = 0 in
  >>>>x

• let g:haskell_indent_where = 6

  where f :: Int -> Int
  >>>>>>f x = x

• let g:haskell_indent_before_where = 2

  foo
  >>where

• let g:haskell_indent_after_bare_where = 2

  where
  >>foo

• let g:haskell_indent_do = 3

  do x <- a
  >>>y <- b

• let g:haskell_indent_in = 1

  let x = 1
  >in x

• let g:haskell_indent_guard = 2

  f x y
  >>|

This plugin also supports an alterative style for case indentation.

• let g:haskell_indent_case_alternative = 1

  f xs ys = case xs of
  >>[]     -> ...
  >>(y:ys) -> ...

Cabal

• let g:cabal_indent_section = 2 (limited to max. 4 spaces)

  executable name
  >>main-is:             Main.hs

Using hindent

Additionally you can use the vim-hindent plugin to achieve automatic indentation using hindent. Mind that hindent itself recommends to just use formatprg feature for this purpose:

setlocal formatprg=hindent

And then press gq to reformat. See :help 'formatprg' and :help gq for detauls.

Author

• Original author of the haskell-vim plugin: raichoo
• Author/maintainer of this fork: Viacheslav Lotsmanov