Carousel: Enable core lightbox on single image blocks

[ryelle]

Fixes #36820

Proposed changes:

This PR removes the code to disable the core lightbox feature. As noted in this comment thread, the core feature is better for single image blocks, so it should not be disabled. The Jetpack carousel is still used for galleries though, so there is also code to remove the lightbox settings on image blocks in galleries (otherwise you get a double-lightbox view).

Screenshots

The setting is back on Image blocks.

On the front end, the core lightbox is used, you can tell by hovering over the image and seeing the "Expand" icon button (focused here).

The core lightbox setting is also available on galleries, but it does nothing different when applied (in fact, as far as I can tell, none of these have any effect, it always uses the JP Carousel).

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:

1. Check that Carousel is enabled in Jetpack > Settings > Writing tab > Media section
2. Create or edit a post with images
3. When inserting an image block, you should see the option to link to "Enlarge on click"
4. On the front end, it should use the core lightbox
5. When inserting a gallery block, you'll also see an option to "Enlarge on click"
6. On the front end, it will still use the Jetpack Carousel

The expected behavior, for each click option:

	Carousel enabled	Carousel disabled
Image: image file	image file	image file
Image: attachment	Jetpack Carousel	attachment page†
Image: enlarge	Core lightbox	Core lightbox
Gallery: image file	Jetpack Carousel	image file
Gallery: attachment	Jetpack Carousel	attachment page†
Gallery: enlarge	Jetpack Carousel‡	Core lightbox
Gallery: none	Jetpack Carousel‡	nothing

† The attachment page will redirect to image file on newer installs, since attachment pages have been disabled (see WordPress/gutenberg#56019). It is kind of strange that the attachment page == carousel, but that's the current behavior.
‡ Since there is no link, these don't have an interactive element, and so the carousel cannot be activated by keyboard. The fact that the carousel still opens on "none" has already been reported #28030.

[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 (Jetpack), and enable the update/carousel-core-lightbox-images branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack update/carousel-core-lightbox-images

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]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/modules/carousel/jetpack-carousel.php	54/605 (8.93%)	0.15%	-10 💚

Full summary · PHP report · JS report