Language Server

The lsp command starts the Beacon Language Server Protocol server for editor integration.

Usage

beacon-cli lsp [OPTIONS]

Options

--tcp <PORT> - Use TCP on the specified port (TODO: not yet implemented)
--log-file <PATH> - Write logs to the specified file

Communication Modes

stdio (Default)

The default mode uses standard input/output for LSP communication. This is the standard mode for editor integration:

beacon-cli lsp

Editors spawn the LSP server and communicate via pipes. This is automatically configured by editor plugins.

TCP Mode (TODO)

TCP mode allows remote LSP connections and easier debugging:

beacon-cli lsp --tcp 9257

Logging

stderr (Default)

By default, logs are written to stderr:

beacon-cli lsp 2> lsp.log

File Logging

Use the --log-file option to write logs to a specific file:

beacon-cli lsp --log-file /tmp/beacon-lsp.log

The log file is created if it doesn't exist and appended to if it does.

Environment Variables

Control log level via the RUST_LOG environment variable:

# Info level (default)
RUST_LOG=info beacon-cli lsp

# Debug level for verbose logging
RUST_LOG=debug beacon-cli lsp

# Trace level for very verbose logging
RUST_LOG=trace beacon-cli lsp

Editor Integration

VS Code

The Beacon VS Code extension automatically spawns the LSP server. No manual configuration needed.

Neovim

Configure nvim-lspconfig:

require'lspconfig'.beacon.setup{
  cmd = { "beacon-cli", "lsp" },
  filetypes = { "python" },
  root_dir = function(fname)
    return vim.fn.getcwd()
  end,
}

Emacs (lsp-mode)

Add to your configuration:

(add-to-list 'lsp-language-id-configuration '(python-mode . "python"))
(lsp-register-client
 (make-lsp-client :new-connection (lsp-stdio-connection '("beacon-cli" "lsp"))
                  :major-modes '(python-mode)
                  :server-id 'beacon))

LSP Features

The Beacon LSP server provides:

Full type inference (Hindley-Milner)
Hover information with inferred types
Go to definition
Find references
Document/workspace symbols
Semantic tokens
Inlay hints (type annotations)
Code actions
Diagnostics (type errors)
Auto-completion

See the LSP documentation for detailed feature descriptions.

Beacon.rs