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Copilot Instructions

This is the official Prettier VS Code extension (prettier.prettier-vscode). It provides code formatting using Prettier for Visual Studio Code, supporting JavaScript, TypeScript, CSS, HTML, Vue, and many other languages.

Development

  • Use npm as the package manager
  • Run npm install to install dependencies
  • Run npm run compile to build for development
  • Run npm run test to run tests (no VS Code instance can be running)
  • Run npm run lint to check linting
  • Run npm run prettier to format code

Architecture

Entry points:

  • Desktop: src/extension.ts → bundled to dist/extension.js
  • Browser: Same entry, bundled to dist/web-extension.js (uses BrowserModuleResolver instead of ModuleResolver)

Core components:

  • src/extension.ts - Extension activation, creates ModuleResolver, PrettierEditService, and StatusBar
  • src/PrettierEditService.ts - Registers VS Code document formatting providers, handles format requests
  • src/ModuleResolver.ts - Resolves local/global Prettier installations, falls back to bundled Prettier
  • src/PrettierInstance.ts - Interface for Prettier loading, with PrettierMainThreadInstance and PrettierWorkerInstance implementations

esbuild produces two bundles:

  • Node bundle (dist/extension.js) for desktop VS Code
  • Web bundle (dist/web-extension.js) for vscode.dev/browser

Code Style

  • Use TypeScript for all source code
  • Follow existing code patterns in the codebase
  • Extension settings are prefixed with prettier. and defined in package.json
  • Use the VS Code extension API patterns already established in the codebase

Testing

  • Test fixtures live in test-fixtures/ with their own package.json and Prettier configurations
  • The .do-not-use-prettier-vscode-root marker file stops module resolver from searching above test fixtures
  • Tests run inside a VS Code instance using the Extension Development Host

Code Review Guidelines

When reviewing pull requests, focus on:

Security

  • No hardcoded secrets or credentials
  • Workspace Trust is respected when resolving modules from untrusted workspaces
  • User input is validated before use in file paths or module resolution

VS Code Extension Best Practices

  • Disposables are properly registered with context.subscriptions to prevent memory leaks
  • Async operations handle errors appropriately
  • User-facing messages go through LoggingService or VS Code's message APIs
  • Settings changes are handled correctly (some require reload)

Prettier Compatibility

  • Changes work with both Prettier v2 (sync) and v3+ (async/worker)
  • Module resolution fallback chain is maintained: local → global → bundled
  • Config file watching covers all Prettier config formats

Performance

  • Avoid blocking the extension host main thread
  • PrettierWorkerInstance runs Prettier in a worker thread to avoid blocking
  • Module and config resolution results are cached appropriately

Browser Compatibility

  • Code in the main bundle should work in both Node.js and browser contexts
  • Browser-specific code uses BrowserModuleResolver
  • No Node.js-only APIs in shared code paths