React Compatibility: Replace legacy ReactDOM.render method with createRoot.

[coder-karen]

Fixes #38644

Proposed changes:

• This PR changes ReactDOM.render usage to be via ReactDOM.createRoot, to ensure compatibility with React 19.
• Additionally, in projects/packages/forms/src/dashboard/index.js there was an additional deprecated function being used - unescape. This has been replaced with decodeURIComponent.
• Also, the frontend-management.js file is no longer imported anywhere - it used to be most recently in the Map block (removed here). However, the file may be used in the future based on this issue - Blocks: Convert blocks to use FrontendManagement #15838 - so I've left it with changes and presumably any hiccups when importing down the line will be able to be resolved then.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

#38644

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

In all the below examples, the following console warning should be gone with the branch checked out: Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead., and visible on trunk.

Testing on self-hosted / Atomic:

• Forms:
  • On the feedback page at /wp-admin/edit.php?post_type=feedback, click 'View' in the top right, and select 'Inbox' to use the new Jetpack forms dashboard. This should enable and take you to /wp-admin/admin.php?page=jetpack-forms#/landing. The page should render as expected.
• Search:
  • Add a Jetpack Search subscription to your test site, and enable Instant Search - /wp-admin/admin.php?page=jetpack#/performance. Navigate to Customberg (/wp-admin/admin.php?page=jetpack-search-configure). The page should render as expected.
  • On Atomic sites, in trunk you'll see two of the ReactDOM.render console errors - the one we're testing is related to jp-search-configure.js and this is the one that disappears. The other comes from widgets.wp.com, so will remain when this branch is checked out.
• AI chat block:
  • Add a Jetpack AI Search block (you may need a Search plan). You don't need to ask a question, just add the block and save. Go to the post / page preview or published version, if published. The block should behave as expected. If you are testing on Atomic, you'll have to make sure the site is public or the block won't work properly.
• Story block:
  • Add a Jetpack Story block to a post or page. Go to the post / page preview or published version, if published. The block should behave as expected.

Testing on Simple:

• Follow the steps as above after following the steps in the generated comment below to apply the changes on your sandboxed site.
  • Script debug won't be enabled, so you won't see the console errors on trunk. In this case we're just testing the functionality.
  • When testing Search, you may need a paid plan (Business includes Instant Search). You can enable Instant Search at /wp-admin/admin.php?page=jetpack-search.
  • When testing AI chat, as with Atomic the site has to be public for this to work.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the update/react-19-compat-ReactDOM-render branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack update/react-19-compat-ReactDOM-render
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

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The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

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Once your PR is ready for review, check one last time that all required checks appearing at the bottom of this PR are passing or skipped.
Then, add the "[Status] Needs Team Review" label and ask someone from your team review the code. Once reviewed, it can then be merged.
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Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen daily.
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly. The next release is scheduled for August 6, 2024 (scheduled code freeze on August 5, 2024).

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[monsieur-z]

The cde changes look good. I tested with a self-hosted site and everything worked as expected