Block Registration: add SlotFill to extend a block's description

[jeherve]

• Primary issue: Block API #41236
• Discussion about this: Blocks: Deprecate non-string descriptions #44455 (comment)

What problem does this address?

It was previously possible to use React nodes in a block's description, like so:

description: (
		<Fragment>
			<p>
				{ __(
					'This block does something really fancy and complex.',
					'my-fancy-complex-block'
				) }
			</p>
			<p>
				{ __( 'Here is a detailed description about the things my block does.', 'my-fancy-complex-block' ) }
			</p>
			<ExternalLink href={ supportLink }>{ __( 'Learn more about how to use me', 'my-fancy-complex-block' ) }</ExternalLink>
		</Fragment>
	),

This allowed adding extra information to a block's description, such as links to support documentation or more.

Unfortunately, this is no longer encouraged since #44455.

What is your proposed solution?

Instead of adding all that information to the block's description itself, and since adding it there can have some unintended side-effects, it would be nice to add a new SlotFill that would be displayed right below the block's description in the editor sidebar, and nowhere else.

[mtias]

@jeherve I'm curious if you'd expect this slot to be rendered wherever a block description is rendered. For example, in block previews in the inserter.

[jeherve]

I would expect it to appear in the primary block sidebar only, not in the previews in the inserter. That's just me though. Maybe this could be a parameter?

[mtias]

So it might be good to contextualize the slot as InspectorBlockInfo or similar instead of something more generic. A parameter would be problematic on its own. it's not easy to anticipate all the contexts in which a description of a block might be rendered where the extender didn't expect.