lfe-ls

LFE Language Server implementation

About ↟

LFE language server written in LFE.

I started this project because I wanted to try LFE in a real project and LFE has a bit of a lack of tooling.
It is largely work in progress. The following LSP functionality is implemented:

• initialize request/response
• initialized notification
• textDocument/didOpen notification which loads and maintains documents in memory.
• textDocument/didChange notification which updates the document in memory. Currently the sync transfers the full document. There is room form optimization here to implement a incremental sync.
• textDocument/didClose notification which deletes the document in memory.
• textDocument/didSave notification
• textDocument/completion request/response implements global symbols and loaded modules as well as module functions.
• textDocument/publishDiagnostics notification to push compile diagnostics on saving a file.
• textDocument/hover request/response that shows module/function documentation

didOpen and didSave will compile the source file on the server to provide diagnostics to the client. However, this does not replace the C-c-k key sequence to compile the and reload the module in the REPL in order to take the changes into effect.

Planned further support is:

• showing signature support for functions

Auto-completion is rudimentary right now. It completes global symbols/atoms, functions/macros and functions on a module basis by parsing the text and looking for ':' character which indicates completing for a module. There is a lot of room for improvement. I.e.: functions within a module could be parsed from the text, or variables within a let.

Emacs lfe-mode tweaks

To allow Emacs with Eglot (or also lsp-mode) to trigger completion on : character one has to tweak the lfe-mode to change lfe-mode-syntax-table and set : to be a punctuation character. Here is the full function (found in lfe-mode.el):

(defvar lfe-mode-syntax-table
  (let ((table (copy-syntax-table lisp-mode-syntax-table)))
    ;; Like scheme we allow [ ... ] as alternate parentheses.
    (modify-syntax-entry ?\[ "(]  " table)
    (modify-syntax-entry ?\] ")[  " table)
    ;; ":" character should be used as punctuation to separate symbols
    (modify-syntax-entry ?: "." table)
    table)
  "Syntax table in use in Lisp Flavoured Erlang mode buffers.")

Support for ltest

lfe-ls automatically adds _build/test/lib as include to the compiler. So if ltest is added as a test dependency then its includes like:

(include-lib "ltest/include/ltest-macros.lfe")

will automatically be found.

Project support

In order to allow lfe-ls to work with a workspace folder it is a must to create a git repository in the folder your are operating. That will Emacs to recognize the folder as a project.

Build ↟

Compile with:

$ rebar3 lfe compile

To create a release do:

$ rebar3 as prod do clean,release,escriptize

An executable can be started as _build/prod/bin/lfe-ls.

Eglot for Emacs:

To add lfe-ls as a server in Eglot the following can be added to the Eglot config:

(add-to-list
   'eglot-server-programs
   '(lfe-mode . ("/path/to/lfe-ls/_build/prod/bin/lfe-ls"
                 "--transport" "tcp" "--port" :autoport)))

Start the Project REPL ↟

$ rebar3 lfe repl

Starting the repl in this way wilkl automatically start the lfe-ls application and ls server.

Tests ↟

$ rebar3 as test eunit

License ↟

Apache License, Version 2.0

Copyright © 2022, Manfred Bergmann mb@software-by-mabe.com.