wp-includes/block-supports/custom-css.php:162Registers the style block attribute for block types that support it.
$block_typeWP_Block_Typefunction wp_register_custom_css_support( $block_type ) { // Setup attributes and styles within that if needed. if ( ! $block_type->attributes ) { $block_type->attributes = array(); } // Check for existing style attribute definition e.g. from block.json. if ( array_key_exists( 'style', $block_type->attributes ) ) { return; } $has_custom_css_support = block_has_support( $block_type, array( 'customCSS' ), true ); if ( $has_custom_css_support ) { $block_type->attributes['style'] = array( 'type' => 'object', ); }}Unchanged from 7.0.4 through 7.1.0.
Signature, return type and hooks compared across 2 parsed releases.
src/wp-includes/block-supports/custom-css.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.