Language Server Protocol (LSP) implementation for Vim script, written in Rust.

• Diagnostics (syntax errors + lint rules)
• Completion (built-in functions + user-defined symbols with scope support)
• Go to definition (same file + cross-file autoload support)
• Hover information (function signatures, autoload file paths)
• Find references (same file + cross-file)
• Document symbols (outline)
• Rename (cross-file support)
• Signature help (parameter info on function calls)
• Workspace symbols (project-wide symbol search)
• Document highlight (highlight symbol under cursor)
• Folding range (function/if/for/while/try/augroup)
• Selection range (smart expand selection via syntax tree)
• Code actions (quick fixes for lint rules)
• Formatting (configuration)

Total: 786 functions

Total: 149 variables

Only variables with help documentation tags are supported. Runtime-defined variables (e.g., g:markdown_* syntax options) are excluded due to dynamic naming and noise.

• Rust 1.85+
• Nix (optional, for development environment)

nix run github:kawarimidoll/hjkls

Add to your flake.nix inputs:

{
  inputs = {
    hjkls.url = "github:kawarimidoll/hjkls";
    # ...
  };
}

Then add to your home configuration:

{ inputs, pkgs, ... }:
{
  home.packages = [
    inputs.hjkls.packages.${pkgs.system}.default
  ];
}

cargo install --git https://github.com/kawarimidoll/hjkls

vim.lsp.config("hjkls", {
  cmd = { "/path/to/hjkls" },
  filetypes = { "vim" },
  root_markers = { ".git" },
})

vim.lsp.enable("hjkls")

yegappan/lsp is a Vim9 script-based LSP client.

let lspServers = [#{
      \   name: 'hjkls',
      \   filetype: ['vim'],
      \   path: '/path/to/hjkls',
      \   args: [],
      \ }]

let lspOptions = #{
      \   autoComplete: v:true,
      \   autoHighlight: v:true,
      \   showDiagWithVirtualText: v:true,
      \   showSignature: v:true,
      \ }

autocmd VimEnter * ++once call LspOptionsSet(lspOptions) | call LspAddServer(lspServers)

vim-lsp is a popular async LSP client.

augroup hjkls_lsp
  autocmd!
  autocmd User lsp_setup call lsp#register_server({
        \ 'name': 'hjkls',
        \ 'cmd': ['/path/to/hjkls'],
        \ 'allowlist': ['vim'],
        \ })
augroup END

let g:lsp_diagnostics_enabled = 1
let g:lsp_diagnostics_virtual_text_enabled = 1

Neovim 0.11:

vim.api.nvim_create_autocmd("LspAttach", {
  callback = function(args)
    vim.opt.completeopt = { "menuone", "noselect", "fuzzy" }
    local client = vim.lsp.get_client_by_id(args.data.client_id)
    if client and client:supports_method("textDocument/completion") then
      vim.lsp.completion.enable(true, client.id, args.buf, { autotrigger = true })
    end
  end,
})

Neovim 0.12+ (nightly):

vim.api.nvim_create_autocmd("LspAttach", {
  callback = function(args)
    -- 'complete' with 'o' flag: include omnifunc (LSP) in CTRL-N/P completion
    -- 'autocomplete': trigger completion automatically as you type
    vim.bo[args.buf].complete = ".,o"
    vim.bo[args.buf].autocomplete = true
    vim.opt.completeopt = { "menuone", "noselect", "fuzzy" }
  end,
})

-- Highlight references to the symbol under cursor
vim.api.nvim_create_autocmd({ "CursorHold", "CursorHoldI" }, {
  callback = function()
    if #vim.lsp.get_clients({ bufnr = 0 }) > 0 then
      vim.lsp.buf.document_highlight()
    end
  end,
})
vim.api.nvim_create_autocmd({ "CursorMoved", "CursorMovedI" }, {
  callback = function()
    vim.lsp.buf.clear_references()
  end,
})

-- Enable LSP folding (zc=close, zo=open, zR=open all, zM=close all)
vim.api.nvim_create_autocmd("LspAttach", {
  callback = function(args)
    local client = vim.lsp.get_client_by_id(args.data.client_id)
    if client and client:supports_method("textDocument/foldingRange") then
      vim.wo[args.buf].foldmethod = "expr"
      vim.wo[args.buf].foldexpr = "v:lua.vim.lsp.foldexpr()"
      vim.wo[args.buf].foldlevel = 99 -- start with all folds open
    end
  end,
})

cp .envrc.sample .envrc
direnv allow

just          # Show available commands
just build    # Build debug binary
just release  # Build release binary
just check    # Run clippy and check
just fmt      # Format code (Rust, Markdown, YAML, Nix)
just test     # Run tests
just dev-nvim # Open sample file in Neovim for manual testing
just dev-vim  # Open sample file in Vim for manual testing

tree-sitter-vim (v0.4.0) cannot correctly parse <Cmd>...<CR> style mappings (e.g., nmap qu <Cmd>quit<CR>). The grammar's command_argument: /\S+/ greedily consumes <CR>, preventing _map_rhs_statement from recognizing its closing token. This causes the parser to emit ERROR or MISSING nodes.

hjkls includes a workaround to detect and suppress these false positives so that valid <Cmd> mappings do not appear as syntax errors.

• tower-lsp-server - LSP server framework for Rust
• texter - Text management library with tree-sitter integration
• tree-sitter-vim - Vim script grammar for tree-sitter
• salsa - Incremental computation framework
• vim-language-server - Prior art: Vim script LSP in TypeScript

MIT