Blocks: Add isDefault to server side block styles registry

[gziolo]

Moved from GitHub (​https://github.com/WordPress/gutenberg/issues/30356, reported by ​xavivars).

What problem does this address?

[As documented here](​https://github.com/WordPress/gutenberg/blob/trunk/docs/reference-guides/filters/block-filters.md#block-style-variations), block styles can be registered both server side (using PHP method register_block_style) and client side (using wp.blocks.registerBlockStyle).

While server-side registration is a convenient method to easily register new block styles, it lacks the ability to register a style as the default one.

As an example, something that could easily be achieved like this in JS, is not doable in PHP

wp.blocks.registerBlockStyle( 'core/heading', [ 
	{
		name: 'default',
		label: 'Default',
		isDefault: true,
	},
	{
		name: 'alt',
		label: 'Alternate',
	}
]);

What is your proposed solution?

Extend register_block_style to also accept isDefault.
(it would probably require to change core code in ​https://github.com/WordPress/WordPress/blob/59d32bfe24cee58554ac82573d8a69dd6b6749ab/wp-includes/script-loader.php#L2311 )

[mukesh27]

Initial patch

[mukesh27]

Hi there!

Initital 53006.patch​ patch uploaded.

[gziolo]

That was quick, I will test next week if nobody beats me up to it :)

[xavivars]

So it seems it sounds like a idea. I didn't push a patch because I wanted to see what people thought before, via the github issue, but I'm glad you agree with the proposal

[gziolo]

This will require additional changes in ​https://developer.wordpress.org/block-editor/reference-guides/filters/block-filters/.

Given that I see inline_style and style_handle fields that use snake case, I'm leaning towards is_default.

I tested with

register_block_style(
    'core/list',
    array(
        'name'         => 'green-list',
        'label'        => __( 'Green List' ),
    )
);
register_block_style(
    'core/list',
    array(
        'name'         => 'blue-list',
        'label'        => __( 'Blue List' ),
        'is_default'   => true,
    )
);

I can confirm that it correctly applies changes with the example used.

[gziolo]

In 50703:

Blocks: Add is_default handling to server side block styles registry

Ensures that register_block_style lets developer pass is_default flag to mark one of the block style variations as the default one.

Props mukesh27, xavivars.
Fixes #53006.

[gziolo]

Documentation changes applied on the Gutenberg project side in ​https://github.com/WordPress/gutenberg/pull/30792.