README.org

lang/haskell

Table of Contents

• Description
  • External resources
  • Module Flags
  • Plugins
• Prerequisites
  • Cabal
  • LSP (haskell-ide-engine)
  • LSP (ghcide)
  • Stack
  • Haskell packages
• Configuration
  • Using the new-style cabal REPL
• Troubleshooting

Description

This module adds Haskell support, powered by either dante (the default) or LSP (haskell-language-server or ghcide).

• Code completion (company-ghc)
• Look up documentation (hoogle)
• eldoc support (dante)
• REPL (ghci)
• Syntax-checking (flycheck)
• Code navigation (dante)
• Snippets

External resources

Here are a few resources I’ve found indispensable in my Haskell adventures:

• Learn you a haskell for great good
• Haskell Programming from first principles
• Awesome Haskell: an extensive list of haskell resources
• The Haskell Tool Stack docs

Module Flags

• +dante Enables dante; a fork of intero aimed at lightweightedness. It doesn’t depend on stack, supports both cabal-only and stack projects, but lacks eldoc support.
• +ghcide Enables LSP support with ghcide (requires the :tools lsp module).
• +lsp Enables LSP support with haskell-ide-engine (requires the :tools lsp module).

Plugins

• haskell-mode
• +dante
  • dante
  • attrap
• +lsp
  • lsp-haskell

Prerequisites

Depending on whether you use Dante, haskell-language-server or ghcide, your dependencies will differ:

• Dante users need cabal, ghc and ghc-mod
• LSP users need the haskell-ide-engine LSP server OR ghcide
• All users will need the hoogle package

Cabal

To use Dante, you need cabal (the haskell package builder) and ghci (the compiler, syntax checker & repl):

MacOS

brew install cabal-install ghc

Arch Linux

sudo pacman -S cabal-install ghc

openSUSE

sudo zypper install cabal-install ghc

LSP (haskell-ide-engine)

You will need stack and git installed.

You will find a comprehensive install guide for haskell-ide-engine on its project page, but here’s a TL;DR:

MacOS

haskell-ide-engine must be build and installed manually on MacOS, e.g.

git clone https://github.com/haskell/haskell-ide-engine
cd haskell-ide-engine
make

Arch Linux

haskell-ide-engine-git is available on the AUR

yay -S haskell-ide-engine-git

LSP (ghcide)

See https://github.com/digital-asset/ghcide for install instructions.

Stack

To use LSP, you need stack:

MacOS

brew install haskell-stack
stack setup

Arch Linux

sudo pacman -S stack
# Replace pacaur with your AUR package manager of choice
pacaur -S ncurses5-compat-lib
stack setup

openSUSE

sudo zypper install stack
stack setup

Haskell packages

You’ll need to install the following packages using stack or cabal:

• (Dante users) ghc-mod

  stack install ghc-mod
  # or
  cabal install ghc-mod
      

• hoogle

  cabal update
  cabal install happy haskell-src-exts   # ghc-mod/hoogle dependencies
  cabal ghc-mod hoogle
  # or
  stack install ghc-mod
  stack install hoogle
      

And ensure the binaries for these packages are in your PATH, e.g.

# place this in your profile file, like ~/.bash_profile or ~/.zshenv
export PATH="~/.local/bin:$PATH"

Configuration

Using the new-style cabal REPL

haskell-mode will typically detect what REPL to run based on your project (e.g. stack, (old-style) cabal or ghc). If you want the new-style cabal REPL you must set haskell-process-type manually:

(setq haskell-process-type 'cabal-new-repl)

Troubleshooting

• Stack users: a dist/setup-config file in your project may cause ghc-mod to not work.