wp_register_custom_classname_support() │ WP 5.6.0

Registers the custom classname block attribute for block types that support it.

Internal function — this function is designed to be used by the kernel itself. It is not recommended to use this function in your code.

No Hooks.

Returns

null. Nothing (null).

Usage

wp_register_custom_classname_support( $block_type );
$block_type(WP_Block_Type) (required)
Block Type.

Changelog

Since 5.6.0 Introduced.

wp_register_custom_classname_support() code WP 7.1.2

wp-includes/block-supports/custom-classname.php 
function wp_register_custom_classname_support( $block_type ) {
	$has_custom_classname_support = block_has_support( $block_type, 'customClassName', true );

	if ( $has_custom_classname_support ) {
		if ( ! $block_type->attributes ) {
			$block_type->attributes = array();
		}

		if ( ! array_key_exists( 'className', $block_type->attributes ) ) {
			$block_type->attributes['className'] = array(
				'type' => 'string',
			);
		}
	}
}