lsp-haskell

An Emacs Lisp library for interacting with a Haskell language server such as haskell-language-server using Microsoft's Language Server Protocol.

The library acts as a client for lsp-mode.

Functionality

This main functionality of lsp-haskell is:

Finding and launching the haskell-language-server binary
Providing configuration options to haskell-language-server

If you would like to know about how LSP functionality is provided in Emacs and how to use it, please consult lsp-mode. If you would like to know about the LSP functionality which is provided by the Haskell language server, please consult haskell-language-server.

Installation

Follow the lsp-mode installation instructions. Do not skip this! It has important information.

lsp-mode automatically requires the lsp-haskell package , so you do not need to require lsp-haskell unless you like being explicit. Similarly, lsp-haskell automatically requires the haskell-mode package, so you do not need to require haskell-mode.

You will need to set some hooks to ensure that lsp-mode is triggered when the haskell-mode major mode is entered.

(add-hook 'haskell-mode-hook #'lsp)
(add-hook 'haskell-literate-mode-hook #'lsp)

Configuration

HLS has some configuration you can modify using either the lsp-haskell or lsp customization groups:

(customize-group 'lsp-haskell)

; or

(customize-group 'lsp)

If you want to modify some configuration that this project doesn't support yet you can customize things explicitly yourself using lsp--set-configuration. For example:

(add-hook 'lsp-after-initialize-hook
          '(lambda ()
             (lsp--set-configuration
              '(:haskell (:plugin (:tactics (:config (:timeout_duration 5)))))
              )))

Language server installation

Follow the instructions on the haskell-language-server repositories to install the server binaries.

If you have installed the binaries to a location that is not on your PATH, or you are not using the haskell-language-server-wrapper, then you will need to customize the lsp-haskell-server-path variable to point to the executable you want to launch.

Server configuration

lsp-haskell provides a few options for for setting the server executable and arguments, and numerous settings for configuring the server itself (hlint, choice of formatting provider, etc.).

Note that server configuration settings will currently not be applied until the server is restarted.

Troubleshooting

lsp-haskell is just the glue between lsp-mode and haskell-language-server.

If you have an issue with Emacs, it is probably a lsp-mode issue. If you have an issue with the Haskell functionality itself, it is probably a haskell-language-server issue. If you have an issue specifically with how the two are joined together, then it belongs here!

If you're not sure what the problem is, the haskell-language-server README provides some troubleshooting instructions.

emacs-lsp / lsp-haskell

readme