just-lsp

just-lsp is a server implementation of the language server protocol for just, the command runner.

Installation

just-lsp should run on any system, including Linux, MacOS, and the BSDs.

The easiest way to install it is by using cargo, the Rust package manager:

cargo install just-lsp

Otherwise, see below for the complete package list:

Cross-platform

Package Manager	Package	Command
Cargo	just-lsp	cargo install just-lsp

Linux

Operating System	Package Manager	Package	Command
Arch	pacman	just-lsp	pacman -S just-lsp

Pre-built binaries

Pre-built binaries for Linux, MacOS, and Windows can be found on the releases page.

Usage

just-lsp can be used with any LSP client, this section documents integration with some of the more popular ones.

Neovim

You can use the release build of just-lsp by setting up the just server on lspconfig, so somewhere in your config:

local lsp = require('lspconfig')

lsp.just.setup({
  -- ...
})

This assumes just-lsp is installed on your system and is in your $PATH.

Features

The server implements a decent amount of the language server protocol specification. This section aims to document some of them.

textDocument/codeAction

We provide a code action for each recipe. These code actions run the selected recipe using just, populating a buffer with its output (stderr + stdout).

textDocument/completion

Completions are provided to you as you type. We currently show recipes, built-in functions, and constants.

textDocument/definition

You're able to go to a recipe, parameter or assignment definition from an identifier.

textDocument/documentHighlight

Like references, but highlights them inside the document.

textDocument/foldingRange

Code folding for recipes.

textDocument/formatting

You're able to format your justfile. This calls just --fmt --unstable and writes the result to your buffer.

textDocument/hover

You can request hover information for syntactic elements like recipes, built-in functions, constants, etc. and see information about them.

textDocument/publishDiagnostics

We try to publish useful diagnostics. Some of them include checks for non-existent aliases, dependencies, and syntax errors.

textDocument/references

All references to an identifier can be shown. This includes aliases, dependencies, recipes, and more.

textDocument/rename

Workspace-wide symbol renaming is supported.

Development

I use Neovim to work on this project, and I load the development build of this server to test out my changes instantly. This section describes a development setup using Neovim as the LSP client, for other clients you would need to look up their respective documentation.

First, clone the repository:

git clone https://github.com/terror/just-lsp

Build the project:

cd just-lsp
cargo build

Add this to your editor configuration:

local lsp = require('lspconfig')

local configs = require('lspconfig.configs')

if not configs.just_lsp then
  configs.just_lsp = {
    default_config = {
      cmd = { '/path/to/just-lsp/target/debug/just-lsp' },
      filetypes = { 'just' },
      root_dir = function(fname)
        return lsp.util.find_git_ancestor(fname)
      end,
      settings = {},
    },
  }
end

local on_attach = function(client)
  -- Add your implementation here
end

local capabilities = {} -- Define what functionality the LSP client is able to handle

lsp.just_lsp.setup({
  on_attach = on_attach,
  capabilities = capabilities,
})

n.b. You'll need to replace /path/to/just-lsp/target/debug/just-lsp with the actual absolute path to the binary.

on_attach is a function that gets called after an LSP client gets attached to a buffer, mine just sets up a few mappings:

local on_attach = function(client)
  client.server_capabilities.semanticTokensProvider = nil

  map('n', '<leader>ar', '<cmd>lua vim.lsp.buf.rename()<CR>')
  map('n', '<leader>s', '<cmd>lua vim.lsp.buf.format({ async = true })<CR>')
  map('n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>')
  map('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>')
  map('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>')
  map('n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>')
end

...and capabilities is a table defining what functionality the LSP client is able to handle, I use default capabilities provided by cmp-nvim-lsp:

local capabilities = require('cmp_nvim_lsp').default_capabilities()

n.b. This will require you to have the nvim-lspconfig (and optionally cmp-nvim-lsp) plugin installed.

Prior Art

Check out just, the command runner.