Likes and sharing panel: Render on demand

[sirreal]

Likes and sharing are two independent plugins that render checkboxes in the same panel of the Jetpack sidebar.

There is an issue where the absence of other, unrelated sidebar panels causes the entire sidebar to be hidden, unintentionally hiding likes and sharing options:

jetpack/extensions/shared/jetpack-plugin-sidebar.js

Lines 23 to 37 in 08a66d7

	if ( ! fills.length ) {
	return null;
	}
	return (
	<Fragment>
	<PluginSidebarMoreMenuItem target="jetpack" icon={ <JetpackLogo /> }>
	Jetpack
	</PluginSidebarMoreMenuItem>
	<PluginSidebar name="jetpack" title="Jetpack" icon={ <JetpackLogo /> }>
	{ fills }
	<JetpackLikesAndSharingPanel.Slot />
	</PluginSidebar>
	</Fragment>
	);

---

The likes and sharing panel becomes another plugin, very similar to the Jetpack sidebar. This allows slot/fill to work correctly at all the levels. It is an independent plugin so that it can register (render) the slot 1 time while being used by 0 or more independent plugins to cause the panel to render 0 or 1 times as necessary.

The panel is also a true fill of the Jetpack sidebar, fixing the initial problem where it was a sibling of the fills. The sidebar is not rendered if there are no fills, which is why the sibling approach was a problem. As a true fill, the existing mechanism to show/hide the sidebar remains untouched.

This PR also includes some Janitorial work around the existing sidebar and the slot/fills:

• Better use of named/default exports
• Do not attach slot to the fill as FillComponent.Slot. These slots are not intended to be rendered outside of these components, do not export them.
• Remove redundant component wrapping

---

Testing instructions (from #12045):

1. Edit both posts and pages and ensure that the Jetpack sidebar is visible when necessary (sidebar contains panels).
2. Enable and disable the Likes and Sharing button modules and ensure that checkboxes are only shown for active modules.
3. Finally, ensure the checkboxes still toggle the buttons on the front-end correctly.

---

Supersedes:

• Closes WIP Gutenberg extensions: Never hide the Likes and Sharing sidebar #12045
• Closes Shares and Likes: Fix Sidebar Slot/Fill Logic #12049
• fix/likes-shares-separate-boxes (no PR)

[jetpackbot]

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⚠️	"Proposed changelog entry" is missing for this PR. Please include any meaningful changes

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[simison]

Code looks good and this tests well and identically to #12045 (review)

Earlier behaviour wasn't hiding this only from pages, but also for non-public custom post types such as re-usable blocks where this probably shouldn't show up anyway. tThat's outside this refactoring and a separate bug and not stopping this from being merged.

[roccotripaldi]

Well done! A call to registerPlugin for the Likes and Sharing panel was what my prior implementation was missing. Thanks for fixing that!

[roccotripaldi]

i'll apply manually to .com

[jeherve]

this works well on my end 👍

[sirreal]

This should be good to merged, but I'm blocked by the wpcom check.

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello sirreal! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer, review, and approve D26942-code before merging this PR. Thank you!

[jeherve]

@sirreal Should be good now. D26942-code is the matching WordPress.com diff.

[codebykat]

THANK YOU @sirreal @roccotripaldi @simison @jeherve for moving so fast on this one 🎉

Best way to start a Monday!