REPL, CDP Debugging & Language Server (REPL, Debug & LSP)

High developer velocity requires rich interactive exploration, visual breakpoint debugging, and intelligent IDE completion. Beejs delivers three integrated systems:

1. Interactive REPL (bee repl): Powered by Rustyline with smart multiline detection and persistent command history;
2. CDP Debugger (bee debug / --inspect): Standard Chrome DevTools Protocol compatible endpoint;
3. Language Server (bee lsp): LSP 3.17 compliant server providing real-time diagnostics, formatting, and hover docs.

1. Modern Interactive REPL (bee repl)

Launch the REPL from the command line:

$ bee repl

1.1 Features

• Smart Multiline Block Detection: Automatically shifts to a continuation prompt (... ) when detecting open braces {, unclosed parentheses (, brackets [, or template strings `;
• Persistent History: Automatically saves command history across sessions to ~/.beejs_history with up/down arrow recall;
• Full Line Editing: Emacs-style keybindings, cursor movement, word skipping, and deletion;
• Built-in Directives:
  • .help: View help information;
  • .clear: Clear the console and reset context;
  • .exit: Exit the session cleanly (or press Ctrl+D).

2. Chrome DevTools Protocol Debugging (bee debug)

Beejs implements the standard Chrome DevTools Protocol (CDP). You can attach Chrome DevTools or VS Code to set breakpoints, step through code, and inspect scopes.

2.1 Starting a Debugging Session

# Start and pause on the first statement awaiting debugger
$ bee debug app.ts

# Or with flag
$ bee run --inspect-brk app.ts

Console output:

Debugger listening on ws://127.0.0.1:9229/ws
Visit chrome://inspect in Google Chrome to connect.
Waiting for debugger connection before executing code...

2.2 Connecting in Chrome

1. Open chrome://inspect in Google Chrome or Chromium;
2. Under Remote Target, locate your running Beejs target;
3. Click inspect to launch dedicated DevTools;
4. Set breakpoints, step over (F10), step into (F11), and inspect call stacks and variables.

3. Language Server Protocol (bee lsp)

Beejs includes a Language Server Protocol (LSP 3.17) daemon for editors such as VS Code, Neovim, Helix, and Sublime Text.

3.1 Running the Server

$ bee lsp

3.2 Implemented Capabilities

• textDocument/publishDiagnostics: Pushes AST diagnostics and syntax errors in real-time as you type;
• textDocument/formatting: Calls bee fmt for zero-config document formatting;
• textDocument/hover: Provides rich Markdown tooltips and type signatures for bee:ai, Tensor, LLM, and AgentPipeline.