Code Editor: Fix after private-api removal

[sirreal]

Proposed changes:

Fixes the improved code editor feature after the EditorContentSlotFill private API it relied on was removed in WordPress/gutenberg#72681.

This implements the code editor replacement using the same technique that was used for the CSS editors.

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)?

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

No.

Testing instructions:

Test this out on a WordPress.com simple site.
Without this patch, the improved editor is unavailable and the regular editor is used.

With this patch, the improved editor is shown.

Interact with the improved editor and ensure that changes are correctly synced between the visual and code editors.

[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 WoA dev 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 (WordPress.com Site Helper), and enable the fix/code-editor-private-api branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack-mu-wpcom-plugin fix/code-editor-private-api

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!

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/jetpack-mu-wpcom/src/features/code-editor/class-code-editor.php	0/33 (0.00%)	0.00%	-10 💚

Full summary · PHP report

[ockham]

Confirming that this works as expected!

Before	After

[ockham]

BTW IIUC this was a regression that wasn't detected by tests. Would it make sense to add some minimal e2e coverage (as a follow-up) to make sure it's the improved editor that's being used?

[ockham]

I'm not able to do an in-depth review of the code due to lack of familiarity, but I can confirm that this tests as advertised 👍

[sirreal]

this was a regression that wasn't detected by tests

It was using a private API and designed to fail gracefully falling back to the regular editor. This worked perfectly.

Would it make sense to add some minimal e2e coverage

That's a good idea. I am concerned about making any tests very coupled to the implementation. It may need to examine whether one editor or another is used where the UI is a code editor with the same contents.