Language server protocol (LSP)¶

rumdl includes a built-in LSP server for real-time Markdown linting in your editor.

Starting the server¶

# Default: use stdio (for editor integration)
rumdl server

# With custom config
rumdl server --config .rumdl.toml

# Verbose logging (for debugging)
rumdl server --verbose

# TCP mode (for debugging)
rumdl server --port 9257

Capabilities¶

The rumdl LSP server provides:

Diagnostics: Real-time linting as you type
Code actions: Quick fixes for auto-fixable issues
Document formatting: Format entire document (rumdl fmt)
Range formatting: Format selected text

Editor configuration¶

Neovim (nvim-lspconfig)¶

Add to your Neovim configuration:

-- if you do not use nvim-lspconfig, add this rumdl config
vim.lsp.config("rumdl", {
  cmd = { "rumdl", "server" },
  filetypes = { "markdown" },
  root_markers = { ".git" },
})

vim.lsp.enable("rumdl")

Helix¶

Add to ~/.config/helix/languages.toml:

[language-server.rumdl]
command = "rumdl"
args = ["server"]

[[language]]
name = "markdown"
language-servers = ["rumdl"]

VS Code¶

Install the rumdl VS Code extension from the marketplace.

The extension automatically manages the LSP server.

Zed¶

Add to your Zed settings:

{
  "lsp": {
    "rumdl": {
      "binary": {
        "path": "rumdl",
        "arguments": ["server"]
      }
    }
  },
  "languages": {
    "Markdown": {
      "language_servers": ["rumdl"]
    }
  }
}

Sublime Text (LSP package)¶

Add to LSP settings (Preferences > Package Settings > LSP > Settings):

{
  "clients": {
    "rumdl": {
      "enabled": true,
      "command": ["rumdl", "server"],
      "selector": "text.html.markdown"
    }
  }
}

Emacs (lsp-mode)¶

Add to your Emacs configuration:

(with-eval-after-load 'lsp-mode
  (add-to-list 'lsp-language-id-configuration '(markdown-mode . "markdown"))
  (lsp-register-client
   (make-lsp-client
    :new-connection (lsp-stdio-connection '("rumdl" "server"))
    :major-modes '(markdown-mode)
    :server-id 'rumdl)))

Emacs (eglot)¶

Add to your Emacs configuration:

(with-eval-after-load 'eglot
  (add-to-list 'eglot-server-programs
               '(markdown-mode . ("rumdl" "server"))))

Configuration¶

The LSP server uses the same configuration as the CLI. It automatically discovers .rumdl.toml or pyproject.toml in your project.

You can override the config path:

rumdl server --config /path/to/.rumdl.toml

Or use built-in defaults only:

rumdl server --no-config

Troubleshooting¶

Enable verbose logging¶

rumdl server --verbose

This outputs detailed logs to stderr, which most editors capture in their LSP logs.

Check server is working¶

Test the server manually:

echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{}}}' | rumdl server

You should see a JSON response with server capabilities.

Common issues¶

Diagnostics not appearing:

Ensure the file is recognized as Markdown (check file extension)
Check that rumdl is in your PATH
Look at your editor's LSP logs for errors

Wrong config being used:

Use --verbose to see which config file is loaded
Use --config to specify an explicit path
Use --no-config to ignore all config files