---

name: vscode-extension-dev description: Expert guidance for developing, testing, and publishing Visual Studio Code extensions. Use when building or modifying VS Code extensions.

VS Code Extension Developer Skill

You are an expert in Visual Studio Code extension development. Use this skill to guide the user through the lifecycle of creating, enhancing, and publishing extensions.

1. Project Structure & Manifest (package.json)

The package.json is the manifest file and is crucial for VS Code extensions.

• engines.vscode: Specifies the minimum compatible version of VS Code.
• activationEvents: Array of events that trigger your extension's activation (e.g., onCommand:id, onLanguage:id, workspaceContains:**\/package.json, or *). Note: VS Code 1.74+ handles many activation events automatically based on contribution points.
• contributes: The core configuration for UI elements and capabilities.
  • commands: Register commands visible in the Command Palette.
  • menus: Add commands to menus (e.g., editor/context, view/title).
  • viewsContainers: Add custom sidebars/activity bars.
  • views: Add tree views to containers.
  • configuration: Define user settings.
  • keybindings: Bind commands to keyboard shortcuts.
• main: The entry point file (e.g., ./out/extension.js).

2. Development Workflow

• Setup: Ensure vscode module is installed (npm install vscode). Note: The vscode module is deprecated; use @types/vscode for development and rely on the engine version.
• Running: Press F5 in VS Code to launch the Extension Development Host. This opens a new window with your extension loaded.
• Reloading: Use Ctrl+R (or Cmd+R on Mac) in the Extension Development Host to reload changes.
• Debugging: Set breakpoints in your source code. Use the Debug Console to inspect variables.

3. The vscode API

• vscode.commands: registerCommand to bind logic to command IDs.
• vscode.window:
  • showInformationMessage, showErrorMessage for notifications.
  • createStatusBarItem for status bar entries.
  • createTreeView for custom views.
  • activeTextEditor for the current editor.
• vscode.workspace:
  • getConfiguration for settings.
  • workspaceFolders for open folders.
  • fs for file system operations (use this over Node's fs when possible for remote support).
• vscode.languages: Register completion providers, hover providers, diagnostics, etc.

4. Best Practices

• Lazy Activation: Only activate your extension when necessary. Avoid using * activation unless absolutely required.
• Disposables: Always push created resources (commands, listeners) to context.subscriptions to ensure they are cleaned up when the extension is deactivated.

  Copycontext.subscriptions.push(disposable);
  

• Webviews: Use strict Content Security Policy (CSP). Use asWebviewUri to load local resources.
• Performance: Do not block the main thread. Use async/await for I/O and heavy operations.

5. Testing

• Use @vscode/test-electron or @vscode/test-cli for integration tests.
• Tests run inside a special instance of VS Code.

6. Packaging and Publishing

• Tool: vsce (Visual Studio Code Extensions CLI).
• Install: npm install -g @vscode/vsce.
• Package: vsce package creates a .vsix file.
• Publish: vsce publish uploads to the Marketplace (requires a Personal Access Token).
• Files: Ensure .vscodeignore is configured to exclude development files (src, tsconfig.json, etc.) from the package.

7. Common Tasks

Registering a Command

Copyimport * as vscode from "vscode";

export function activate(context: vscode.ExtensionContext) {
  let disposable = vscode.commands.registerCommand(
    "myExtension.helloWorld",
    () => {
      vscode.window.showInformationMessage("Hello World!");
    },
  );

  context.subscriptions.push(disposable);
}

Tree View Provider

Implement vscode.TreeDataProvider<T>.

• getTreeItem(element: T): vscode.TreeItem
• getChildren(element?: T): ProviderResult<T[]>

Configuration

Access settings defined in package.json:

Copyconst config = vscode.workspace.getConfiguration("myExtension");
const value = config.get("mySetting");