erlang_ls

An Erlang server implementing Microsoft's Language Server Protocol 3.0.

Disclaimer

This project is still under heavy development and it is therefore not still suitable as a fully-functional language server for daily usage. Said that, contributors and early users are extremely welcome.

If you have any issues or questions about the project, feel free to open a new issue. You can also join the #language-server channel in the Erlanger Slack if you would like to get involved or if you prefer a more informal mean of communication.

A wiki is also available and I occasionally blog about the project on Medium.

Minimum Requirements

Erlang OTP 21+
rebar3 3.9.1+

Quickstart

Compile the project:

rebar3 escriptize

Emacs Setup

The official lsp-mode package already includea a client for the Erlang Language Server, so simply add the following to your .emacs file (assuming the erlang_ls executable is available in your PATH:

;; Install the yasnippet dependency
(package-install 'yasnippet)
;; Install the official lsp-mode package
(package-install 'lsp-mode)
;; Enable LSP automatically for Erlang files
(add-hook 'erlang-mode-hook #'lsp)

Ensure you have Erlang (i.e. erl, escript and friends) as part of your Emacs path. If you don't, you can try the following:

;; Ensure your Emacs environment looks like your user's shell one
(package-require 'exec-path-from-shell)
(exec-path-from-shell-initialize)

To enable logging on the client-side, just:

(setq lsp-log-io t)

Features

This section summarizes the functionalities currently implemented by the erlang_ls server.

Code Navigation

Code navigation is currently available for the following elements:

Function applications (both local and remote)
BIFs
Behaviour attributes
Included files
Type definitions
Record definitions
Macro definitions
Export list entries
Import list entries

Code Completion

Completion requests are sent from the client to the server to compute completion items at a given cursor position. Completion items are presented to the user for easy selection.

Code completion are currently triggered by one of the following characters: :.

Code completion is available for the following elements:

Exported functions

Customization

It is possible to customize the behaviour of the erlang_ls server by adding a erlang_ls.config file to the root of your projects.

A sample erlang_ls.config file would look like the following:

otp_path: "/path/to/otp/lib/erlang"
deps_dirs:
  - "lib/*"

Currently, the following customizations are possible:

Parameter	Description
otp_path	Path to the OTP installation
deps_dirs	List of directories containing dependencies. It supports wildcards.

Troubleshooting

It is possible to compile and start the language server in debug mode:

rebar3 as debug escriptize

Ensure you update your PATH to include the new executable which now resides in:

/path/to/erlang_ls/_build/debug/bin/erlang_ls

Once an instance of the server is running you can connect to it via:

erl -sname debug -remsh erlang_ls@`HOSTNAME`

The redbug application is included in debug mode, so feel free to use it.

References

https://microsoft.github.io/language-server-protocol/

License

The erlang_ls project is licensed under the Apache License 2.0. Please refer to the LICENSE file for details.

erszcz / erlang_ls