Lark for Visual Studio Code

The VS Code Lark Parser extension provides rich language support for Lark grammar files.

✨ Features

• ✅ Syntax Highlighting: Complete TextMate grammar for Lark files

  • Rule definitions (lowercase identifiers)
  • Terminal definitions (UPPERCASE identifiers)
  • Directives (%import, %ignore, %declare, %override, %extend)
  • Operators (?, *, +, |, ->, !, ...)
  • Comments (// and #)
  • Number, Strings and regex literals
  • Priority specifications

• ✅ Language Server Protocol (LSP): Full intellisense support

  • Diagnostics: Real-time syntax error detection and validation
  • Code Completion: Intelligent suggestions for rules, terminals, and keywords
  • Hover Information: Documentation and symbol information on hover
  • Go to Definition: Navigate to rule and terminal definitions
  • Find References: Locate all usages of symbols across your grammar
  • Document Symbols: Outline view showing all rules and terminals
  • Semantic Analysis: Advanced grammar validation and error reporting

• ✅ Markdown Integration: Lark code blocks in Markdown files

• ✅ Custom Icons: Dedicated file icons for .lark files

• ✅ Configuration: Customizable language server settings

• ✅ Views & Providers: Tree views for improved workspace navigation

  • Terminals and Rules views provide quick access to terminal and rule definitions
  • Providers are implemented via a generic LarkTreeDataProvider with specialized LarkTerminalProvider and LarkRuleProvider
  • View container and custom icons are included for better discoverability

• ✅ Formatting: Document formatting support via the Lark Language Server

  • Use the built-in "Format Document" command (Shift+Alt+F) or enable format-on-save in VS Code
  • Formatting is provided by the language server (LSP) and requires the bundled or installed server to implement the formatting handlers

📦 Installation

1. Open Visual Studio Code.
2. Go to the Extensions view by clicking on the Extensions icon in the Activity Bar on the side of the window or by pressing Ctrl+Shift+X.
3. Search for "Lark".
4. Click on the "Install" button for the extension named "Lark" [↗] by Dynova [↗].
5. Once installed, you can start using Lark syntax highlighting and intellisense in your .lark files.

🛠️ Requirements

• Python 3.9+: Required for the language server

The extension automatically uses its bundled dependencies and doesn't require Poetry or a virtual environment setup. For development, Poetry is recommended but not required for end users.

Note: The extension can either use the bundled Python environment shipped with the extension or a user-specified Python interpreter (see Configuration). A new command is available to remove the bundled environment if you need a clean re-installation.

⚙️ Configuration

Optional settings you can add to your settings.json:

{
    "files.associations": {
        "*.lark": "lark"
    },
    "lark.server.enabled": true,
    "lark.server.pythonPath": "pythonPath",
    "lark.server.arguments": ["--log-level", "INFO"],
    "lark.server.trace": "off"
}

Server Resolution Order:

1. Custom path: If lark.server.pythonPath is configured, uses that executable

2. Python extension environment: If the official Python extension is installed, uses its selected interpreter

3. System Python: Final fallback to system Python with source path

Language server resolution order:

1. Installed language server: Checks if a language server is installed in the specified Python environment with a supported version.
2. Bundled server: Uses the bundled Python environment.

Important configuration notes:

• lark.server.pythonPath: Set a custom Python executable to run the language server. If unset, the extension will prefer the Python extension's interpreter (if present) or fall back to system Python.
• lark.server.trace: Controls server tracing (off/messages/verbose).
• Formatting: formatting is exposed via the language server; no additional client configuration is required beyond enabling the server.

New commands available in the Command Palette:

• Lark: Show Logs — Open the extension output channel for troubleshooting
• Lark: Restart Language Server — Restart the language server process
• Lark: Remove Bundled Environment — Remove the bundled Python environment so the extension can reinstall it cleanly

Views and how to use them:

• Open the Explorer side bar and look for the "Lark" view container. Inside it you'll find the "Terminals" and "Rules" views which show symbols discovered by the language server. Use the context menu on entries to reveal ranges or perform registered commands.

Virtual workspace support:

• The extension detects virtual workspaces (for example, GitHub Codespaces or remote editors) and adjusts the document selector to include non-file schemes so language features remain available.

📝 Release Notes

All changes are listed in our change log ↗.

🤝 Contributing

Contributions are greatly appreciated. Check the contribution guidelines ↗ for more information.

Please fork this repository and open a pull request to make grammar tweaks, add support for other subgrammars etc.

👥 Contributors

See the list of contributors in our contributors page ↗.

📜 License

This project is licensed under the terms of the Apache-2.0 license. See the LICENSE ↗ file.

⚠️ Disclaimer

The Lark Parser team already provides an extension for Visual Studio Code that includes syntax highlighting as part of the Lark grammar syntax support ↗ published in their github organization Lark Parser ↗, gently provided by Dirk Thomas.

This extension is based on the same grammar but is actively maintained independently by Dynova ↗ as an open source project.