stan-language-server

A language server for the Stan probabilistic programming language written in TypeScript and using Bun to build an executable binary.

Features

• Auto-completion: Keywords, functions, distributions, data types, and constraints
• Hover information: Documentation and type information
• Diagnostics: Real-time syntax and semantic error detection
• Code formatting: Using the official Stan compiler
• Include file support: Full #include resolution and compilation

Editor-specific configuration

VSCode:

Install the extension from Marketplace or open-vsx.

Neovim

There are many ways to install language servers in neovim. Here is one (if you have a different or better way, consider contributing it!):

Download the latest language server executable from GitHub and put it somewhere in your PATH. Then in your nvim config folder add lua/lsp/init.lua with:

local servers = {
    stan_ls = "lsp.stan",
}

local function setup_server(name, config_module)
    local config = require(config_module)

    vim.api.nvim_create_autocmd("FileType", {
        pattern = config.filetypes,
        callback = function()
            if #vim.lsp.get_clients({ bufnr = 0, name = name }) > 0 then
                return
            end

            local root_dir = vim.fs.root(0, config.root_markers)
            print(string.format("Starting %s for buffer %d with root: %s", name, vim.api.nvim_get_current_buf(),
                root_dir or "none"))

            vim.lsp.start({
                name = name,
                cmd = config.cmd,
                root_dir = root_dir,
                initialization_options = config.settings or {},
                on_exit = function(code, signal)
                    print(string.format("%s exited with code %d, signal %d", name, code, signal))
                end,
            })
        end,
    })
end

for server_name, config_path in pairs(servers) do
    setup_server(server_name, config_path)
end

Then in lua/lsp/stan.lua add the following:

return {
    cmd = { "stan-language-server", "--stdio" },
    filetypes = { "stan" },
    root_markers = { ".git" },
    settings = {
        maxLineLength = 78,
        includePaths = {},
    },
}

Zed

Install the Stan extension.

Sublime Text 4

Using LSP for Sublime Text, download the latest release and add the following to the settings file:

{
  "clients": {
    "stan-lsp": {
      "enabled": true,
      "command": ["/YOUR/PATH/TO/stan-language-server", "--stdio"],
      "selector": "source.stan | source.stanfunctions",
      "initializationOptions": {},
      "settings": {
        "stan-language-server": { "includePaths": [], "maxLineLength": 78 }
      }
  }
}

Emacs (eglot)

Assuming you are using stan-ts-mode, download the latest release and add the following to your init.el:

; elgot is built in to emacs 29+, but a similar config would work for lsp-mode
(with-eval-after-load 'eglot
    (add-to-list 'eglot-server-programs
        '(stan-ts-mode . ("/YOUR/PATH/TO/stan-language-server" "--stdio"))))

For developers

Development uses bun

To install dependencies:

bun install

Building a binary executable:

bun build:binary

To run unit tests:

bun test

To run end-to-end tests:

pip install pytest pytest-lsp
bun build:binary && pytest tests/