React 17 to 18 Upgrade Initiative

[rwa-siteimprove]

React 17 to 18 Migration Summary

Successfully migrated the swagger-ui repository from React 17 to React 18, implementing all necessary changes to support React 18's new concurrent rendering features and updated APIs.

Changes Implemented

Dependency Updates:

• Updated React from version 17.0.2 to ^18.2.0
• Updated ReactDOM from version 17.0.2 to ^18.2.0
• Updated react-test-renderer from version 17.0.2 to ^18.2.0
• Replaced @wojtekmaj/enzyme-adapter-react-17 with @wojtekmaj/enzyme-adapter-react-18 (version 0.7.1)

Code Updates:

• Migrated from ReactDOM.render() to ReactDOM.createRoot() API in the core rendering logic
• Implemented a WeakMap-based caching mechanism to prevent creating multiple roots on the same DOM node
• Updated test configuration to use React 18 compatible enzyme adapter
• Imported createRoot from react-dom/client as required by React 18

Compatibility Notes

All existing lifecycle methods in the codebase already use the UNSAFE_ prefix, making them compatible with React 18's StrictMode. React 18's automatic batching feature is enabled by default and will improve performance for state updates outside of React event handlers. No hydration changes were required as the application does not use server-side rendering. The migration maintains full backward compatibility while enabling access to React 18's new concurrent features like startTransition and useDeferredValue if needed in the future.