Installation

A typical haskell-language-server installation consists of:

  • One binary file for each supported ghc version: haskell-language-server-${ghcVersion}

  • Another binary named haskell-language-version-wrapper which analyzes the project or file in the current working dir and calls the appropiate haskell-language-server-${ghcVersion} variant.

    • It accepts all executable arguments from the plain haskell-language-server

Prerequisites

  • For standalone .hs/.lhs files, ghc must be installed and on the PATH. The easiest way to install it is with ghcup or chocolatey on Windows.

  • For Cabal based projects, both ghc and cabal-install must be installed and on the PATH. It can also be installed with ghcup or chocolatey on Windows.

  • For Stack based projects, stack must be installed and on the PATH.

ghcup

If you are using ghcup to manage your installations, you can install haskell-language-server with

ghcup install hls

You can check if HLS is available for your platorm via ghcup here: https://haskell.org/ghcup/install/#supported-platforms.

You can also install HLS from source without checking out the code manually:

ghcup compile hls -v 1.4.0 8.10.7

Check ghcup compile hls --help for a full list of compilation options.

chocolatey

If you are using chocolatey to manage your installations in windows, you can install haskell-language-server with

choco install haskell-language-server

Visual Studio Code

If you are using Visual Studio Code, the Haskell extension will automatically download and install haskell-language-server for you.

Pre-built binaries

There are pre-built binaries available from the releases page for Linux, Windows and macOS. To install, download the haskell-language-server-wrapper executable for your platform as well as any haskell-language-server executables for the GHC versions you plan on working with, and either put them on your PATH or point your client to them.

Arch Linux

The preferred method of installation for development purposes is to use the haskell-language-server-static package from AUR. This package contains statically linked binaries for each supported GHC version and haskell-language-server-wrapper for automatic GHC version selection. It is updated regularly, requires no additional dependencies, and is independent of other haskell packages you may have on your system, including GHC. Its size is relatively large (approx. 900 MB), but if this is a problem for you, during installation you can disable the GHC versions you will not be using by editing the PKGBUILD file.

Alternatively, if you want to use dynamically linked Haskell packages from pacman, you can install the latest pre-compiled version of haskell-language-server from [community]:

sudo pacman -S haskell-language-server

In this case, haskell-language-server is compiled against the GHC distributed to Arch Linux, so you will need maintain a system wide Haskell development environment, and install GHC from pacman as well. See ArchWiki for the details of Haskell infrastructure on Arch Linux.

Fedora

Binary packages for Fedora are available from this Copr repo, built against the official Fedora ghc package.

FreeBSD

HLS is available for installation from official binary packages. Use

pkg install hs-haskell-language-server

to install it. At the moment, HLS installed this way only supports the same GHC version as the ports one.

Installation from source

Common pre-requirements

  • stack or cabal must be in your PATH

    • You need stack version >= 2.1.1 or cabal >= 2.4.0.0

  • git must be in your PATH

  • The directory where stackor cabal put the binaries must be in you PATH:

    • For stack you can get it with stack path --local-bin

    • For cabal it is by default $HOME/.cabal/bin in linux and %APPDATA%\cabal\bin in windows.

Tip: you can quickly check if some command is in your path by running the command. If you receive some meaningful output instead of “command not found”-like message then it means you have the command in PATH.

Linux-specific pre-requirements

On Linux you will need install a couple of extra libraries:

Debian 9/Ubuntu 18.04 or earlier:

sudo apt install libicu-dev libtinfo-dev libgmp-dev zlib1g-dev

Debian 10/Ubuntu 18.10 or later:

sudo apt install libicu-dev libncurses-dev libgmp-dev zlib1g-dev

Fedora:

sudo dnf install libicu-devel ncurses-devel zlib-devel

Windows-specific pre-requirements

In order to avoid problems with long paths on Windows you can do either one of the following:

  1. Clone the haskell-language-server to a short path, for example the root of your logical drive (e.g. to C:\hls). Even if you choose C:\haskell-language-server you could hit the problem. If this doesn’t work or you want to use a longer path, try the second option.

  2. If the Local Group Policy Editor is available on your system, go to: Local Computer Policy -> Computer Configuration -> Administrative Templates -> System -> Filesystem set Enable Win32 long paths to Enabled. If you don’t have the policy editor you can use regedit by using the following instructions here. You also need to configure git to allow longer paths by using unicode paths. To set this for all your git repositories use git config --system core.longpaths true (you probably need an administrative shell for this) or for just this one repository use git config core.longpaths true.

In addition make sure haskell-language-server.exe is not running by closing your editor, otherwise in case of an upgrade the executable can not be installed.

Download the source code

git clone https://github.com/haskell/haskell-language-server --recurse-submodules
cd haskell-language-server

Building

Note, on first invocation of the build script with stack, a GHC is being installed for execution. The GHC used for the install.hs can be adjusted in ./install/stack.yaml by using a different resolver.

Available commands can be seen with:

stack ./install.hs help

Remember, this will take time to download a Stackage-LTS and an appropriate GHC for build haskell-language-server the first time.

Install via cabal

The install-script can be invoked via cabal instead of stack with the command

cabal v2-run ./install.hs --project-file install/shake.project <target>

or using the existing alias script

./cabal-hls-install <target>

Running the script with cabal on windows requires a cabal version greater or equal to 3.0.0.0.

For brevity, only the stack-based commands are presented in the following sections.

Install specific GHC Version

The script will install the executables haskell-language-server-wrapper and haskell-language-server.

It will copy the latter appending the used ghc version, needed by the wrapper to choose the suitable version for the project at hand.

So installing the executables directly with stack install or cabal v2-install may not be enough for it to work properly.

Install haskell-language-server for the latest available and supported GHC version (and hoogle docs):

stack ./install.hs hls

Install haskell-language-server for a specific GHC version (and hoogle docs):

stack ./install.hs hls-8.8.3

hls-8.8.3 target will build the project and install haskell-language-server-wrapper, haskell-language-server, haskell-language-server-8.8.3 and haskell-language-server-8.8 executables.

The Haskell Language Server can also be built with cabal v2-build instead of stack build. This has the advantage that you can decide how the GHC versions have been installed. To see what GHC versions are available, the command cabal-hls-install ghcs can be used. It will list all supported GHC versions that are on the path for build with their respective installation directory. If you think, this list is incomplete, you can try to modify the PATH variable, such that the executables can be found. Note, that the targets hls and data depend on the found GHC versions.

An example output is:

> ./cabal-hls-install ghcs
******************************************************************
Found the following GHC paths:
ghc-8.6.5: /opt/bin/ghc-8.6.5
ghc-8.8.3: /opt/bin/ghc-8.8.3

******************************************************************

If your desired ghc has been found, you use it to install haskell-language-server.

./cabal-hls-install hls-8.6.5

Installation from Hackage

Direct installation from Hackage, while possible via cabal install haskell-language-server, is not recommended for most people. Said command builds the haskell-language-server binary and installs it in the default Cabal binaries folder, but the binary will only work with projects that use the same GHC version that built it.

The package can be found here on Hackage: https://hackage.haskell.org/package/haskell-language-server

Installation via Homebrew

Homebrew users can install haskell-language-server using the following command:

brew install haskell-language-server

This formula contains HLS binaries compiled with GHC versions available via Homebrew; at the moment those are: 8.6.5, 8.8.4, 8.10.7.

You need to provide your own GHC/Cabal/Stack as required by your project, possibly via Homebrew.

Installation using nix

You can read full instructions on how to install HLS with nix in haskell4nix documentation.