seqdiag_formatter

A lightweight Visual Studio Code extension that provides formatting and syntax highlighting for .seqdiag files used with SequenceDiagram.org.

✨ Features

🎯 Formatter

Automatically formats sequence diagram source code:

• Proper indentation for blocks (alt, opt, loop, group, par, etc.)

• Normalizes arrows:

  A->B:hello → A -> B : hello
  

• Fixes spacing around :

• Handles nested blocks correctly

• Converts common mistakes:

  bottom participants → bottomparticipants
  

🎨 Syntax Highlighting

Custom highlighting for better readability:

📦 Installation

Option 1: Install from VSIX

1. Download .vsix file
2. Open VS Code
3. Go to Extensions
4. Click ... → Install from VSIX
5. Select the file

Option 2: Command Line

code --install-extension your-extension-name.vsix

⚙️ Usage

Format Document

• Shortcut:

  Shift + Alt + F
  

• Or enable auto format on save:

{
  "[seqdiag]": {
    "editor.defaultFormatter": "your.publisher-id",
    "editor.formatOnSave": true
  }
}

🧪 Example

Before

bottom participants
User->UI:hello
alt success
UI->API:call
else fail
UI->User:error
end

After

bottomparticipants
User -> UI : hello
alt success
  UI -> API : call
else fail
  UI -> User : error
end

🧠 Supported Syntax

Supports most SequenceDiagram.org features:

• Participants (actor, boundary, control, etc.)
• Messages (->, -->, ->>, etc.)
• Fragments (alt, opt, loop, par, group, ...)
• Notes, boxes, references
• Activations (activate, deactivate)
• Styling and advanced syntax (non-breaking)

⚠️ Limitations

• No AST parsing (text-based formatter)
• No alignment of arrows (yet)
• Does not validate syntax errors

🚀 Roadmap

• Align arrows in columns
• Auto numbering (1. 2. 3.)
• Smarter formatting using AST
• Error detection

🛠 Development

npm install
npm run compile
F5 to run extension

📄 License

MIT License

🙌 Credits

• Inspired by SequenceDiagram.org
• Built for improving .seqdiag developer experience in VS Code