block-mods.php

<?php
/**
 * Plugin Name: Block Modifications
 * Description: A plugin that modifies and extends native Gutenberg Block functionality
 * Author:      Media Mechanics
 * Author URI:  https://mediamechanics.com
 * Version:     1.0
 *
 * @package     BlockMods
 */

namespace BlockMods;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
};

function editor_assets() {
	wp_enqueue_script(
		'block-mods-editor-script',
		plugin_dir_url( __FILE__ ) . 'build/index.js',
		[ 'wp-blocks', 'wp-i18n', 'wp-element', 'wp-editor' ],
		'1.0'
	);
}
add_action( 'enqueue_block_editor_assets', __NAMESPACE__ . '\editor_assets' );


/**
 * Add classes to post-title block
 *
 * @NOTE Post Title Block doens't have a REACT save function so we do this instead
 * to modify the HTML output on the public side. This will not cause a block render
 * issue in admin (i.e. Recover Block) since the block doesn't save any HTML in the editor
 */
function add_post_title_class( $block_content = '', $block = [] ) {
	if ( isset( $block['blockName'] ) && 'core/post-title' === $block['blockName'] ) {
		$defaults = [
			'level' => 2,
			'hasRule' => true,
			'hasTopMargin' => false
		];
		$args = wp_parse_args( $block['attrs'], $defaults );
		$has_green_underline = $args && array_key_exists('hasRule', $args) && $args['hasRule'] === true ? ' has-green-underline ' : ' ' ;
		$has_top_margin = $args && array_key_exists('hasTopMargin', $args) && $args['hasTopMargin'] === true ? ' has-top-margin ' : ' ' ;
		$html = str_replace(
			'wp-block-post-title',
			'wp-block-post-title' . $has_green_underline . $has_top_margin,
			$block_content
		);
		return $html;
	}
	return $block_content;
}
add_filter( 'render_block', __NAMESPACE__ . '\add_post_title_class', 10, 2 );