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name: vscode-extension-builder description: Specialized knowledge for creating, configuring, testing, and publishing VS Code extensions. Use when creating a new VS Code extension from scratch, setting up extension infrastructure (package.json contributes, activation events, testing), configuring extension publishing (.vscodeignore, vsce, marketplace), debugging extension-specific issues (CI failures, marketplace rendering), or implementing extension best practices.

VS Code Extension Creator

Create, configure, test, and publish VS Code extensions with extension-specific best practices.

Core Workflow

1. Initialize - Create package.json with extension manifest
2. Implement - Write extension.ts with activate/deactivate
3. Test - Set up @vscode/test-electron with CI
4. Publish - Bump version, update CHANGELOG, push to main → automated publishing

Publishing Process

1. Update CHANGELOG.md with new version section
2. Bump version in package.json (semantic versioning)
3. Commit and push to main
4. GitHub Actions automatically:
   • Creates Git tag
   • Publishes to marketplace (if version not already published)
   • Skips if tag exists (idempotent)

Critical Learnings

Activation Events

onCommand:extension.commandId (load when command executed) preferred over * (load on startup)

CI Test Workflow

Tests run on pull_request only, not on push to main (avoids redundant post-merge execution)

.vscodeignore

Copy**/*.ts          # Exclude TypeScript
!out/**/*.d.ts   # Include declarations

Linux CI Testing

Requires xvfb-run -a npm test for GUI tests

Marketplace README

Use absolute GitHub URLs: https://raw.githubusercontent.com/user/repo/main/images/demo.png

Version Matching

@types/vscode version must match engines.vscode

References

• package.json - Extension manifest, contributes schema
• testing - @vscode/test-electron, CI setup
• publishing - vsce, .vscodeignore rules
• pitfalls - Common mistakes