wp_register_border_support() │ WP 5.8.0

Registers the style attribute used by the border feature if needed for block types that support borders.

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

Changelog

Since 5.8.0 Introduced.
Since 6.1.0 Improved conditional blocks optimization.

wp_register_border_support() code WP 6.9.1

wp-includes/block-supports/border.php 
function wp_register_border_support( $block_type ) {
	// Setup attributes and styles within that if needed.
	if ( ! $block_type->attributes ) {
		$block_type->attributes = array();
	}

	if ( block_has_support( $block_type, '__experimentalBorder' ) && ! array_key_exists( 'style', $block_type->attributes ) ) {
		$block_type->attributes['style'] = array(
			'type' => 'object',
		);
	}

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