syntax-highlighting-code-comments.php

<?php
/**
 * Plugin Name: Syntax-highlighting Code Comments
 * Plugin URI: https://gist.github.com/westonruter/d35a909df087d90e0100d111eed77faa
 * Description: Extension plugin for Syntax-highlighting Code Block to also add syntax highlighting to code in comments.
 * Version: 0.1.1
 * Author: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * License: GPL2
 * License URI: https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain: syntax-highlighting-code-block
 * Requires PHP: 5.6
 * Gist Plugin URI: https://gist.github.com/westonruter/d35a909df087d90e0100d111eed77faa
 *
 * @package Syntax_Highlighting_Code_Comments
 */

namespace Syntax_Highlighting_Code_Comments;

use WP_Block_Type;
use WP_Block_Type_Registry;

/**
 * Make <code>...</code> in (comment) text syntax-highlighted.
 *
 * The <code> element may be optionally wrapped in a <pre> tags, and then start and end on a line by itself. In other
 * words it must be presented as a block/paragraph and not inline; when <code> appears inline in paragraphs, it will
 * not be syntax-highlighted.
 *
 * @param string $comment_text Comment text.
 * @return string Syntax-highlighted.
 */
function filter_comment_text( $comment_text ) {
	if ( ! function_exists( '\Syntax_Highlighting_Code_Block\render_block' ) ) {
		return $comment_text;
	}

	$registry   = WP_Block_Type_Registry::get_instance();
	$block_type = $registry->get_registered( 'core/code' );
	if ( ! $block_type instanceof WP_Block_Type ) {
		return $comment_text;
	}

	$attributes = [];
	foreach ( $block_type->attributes as $name => $schema ) {
		if ( isset( $schema['default'] ) ) {
			$attributes[ $name ] = $schema['default'];
		}
	}

	$pattern = implode(
		'',
		[
			'(?<=^|\n)',
			'(<pre[^>]*?>\s*)?',
			'<code[^>]*?>(?P<contents>[^<]*?)</code>',
			'(\s*</pre>)?',
			'(?=\r?\n|$)',
		]
	);

	return preg_replace_callback(
		"#{$pattern}#si",
		static function( $matches ) use ( $attributes ) {
			$contents = $matches['contents'];
			$before   = '<pre><code>';
			$after    = '</code></pre>';
			return \Syntax_Highlighting_Code_Block\render_block( $attributes, $before . $contents . $after );
		},
		$comment_text
	);
}

add_filter( 'comment_text', __NAMESPACE__ . '\filter_comment_text', 20 );