Janet LSP

A Language Server (LSP) for the Janet programming language.

Overview

The goal of this project is to provide an augmented editor/tooling experience for Janet, via a self-contained, Language Server Protocol-compliant language server (which is itself implemented in Janet!).

Current features include:

• Auto-completion based on symbols in the Janet Standard Library and defined in user code
• On-hover definition of symbols as returned by (doc ,symbol)
• Inline compiler errors
• Pop-up signature help

Planned features include:

• Jump to definition/implementation
• Find references from definition/implementation
• Refactoring helps
• Symbol renaming helps

Possible (but de-prioritized) features include:

• Syntax highlighting for Janet via semantic tokens

Desirable, but possibly more complicated/difficult features include:

• Stand-alone (i.e. non-Editor-dependent) usage via API/CLI

Caveats

• MacOS support is mostly untested (but as far as I know there shouldn't be major differences).
• The only editor integration currently tested against is Visual Studio Code.
• I've never written a language server before, so I don't really know what I'm doing. Help me, if you'd like!

Clients (i.e. Editors)

Currently, Janet LSP is being regularly tested and is expected to work out of the box with two major editors:

• Visual Studio Code, which you can try/take advantage of by installing the Janet++ extension from the VS Code marketplace, and
• Neovim, which ships with support for LSP servers.

Other editors that implement LSP client protocols, either built-in or through editor extensions, include:

• Emacs
• Vim
• Sublime Text
• Helix
• Kakoune
• Zed

If you get Janet LSP working with any of these options, please let me know!

Getting Started (for Development)

Clone this project and Build the stand-alone binary and .jimage file

Requires Janet and jpm.

$ git clone https://github.com/CFiggers/janet-lsp
$ cd janet-lsp
$ jpm deps
$ jpm build

A .jimage (Janet image) file will be generated in /build. Using a .jimage file makes Janet LSP fully cross-platform (wherever there is a compatible Janet binary on the user's path). But it also means that you must have a Janet binary to use Janet LSP (this author struggles to imagine a scenario where you would both need the LSP and NOT have Janet itself installed).

Installing

After running the commands above, the following command will copy the janet-lsp binscript to a location that can be executed via the command line.

$ jpm install

Test successful install by running the following:

$ janet-lsp --version

Debug Console

Starting in version 0.0.3, you can start a debug console by passing --console to any invocation of Janet LSP, including any of the following:

$ ./build/janet-lsp --console
  OR
$ janet ./build/janet-lsp.jimage --console
  OR
$ janet ./src/main.janet --console

In this mode, the LSP will launch a simple RPC server that listens on port 8037 (by default, configurable with the --debug-port flag). Janet LSPs with version >= 0.0.3 will check for a listening server on port 8037 (or the port specified by --debug-port) and, if found, transmit anything sent through the (logging/log) function to be printed out by the debug console.

In the future, the debug console may function as a networked REPL allowing commands to be sent to the running language server process (but right now it functions in listen-only mode).

Contributions

Issues and Pull Requests welcome.

Prior Art

This project is a hard fork from (with much appreciation to) JohnDoneth/janet-language-server, which is Copyright (c) 2022 JohnDoneth and contributors.