twentytwentyfive-stylesheet-inlining.php

<?php
/**
 * Plugin Name: Twenty Twenty-Five Stylesheet Inlining
 * Plugin URI: https://gist.github.com/westonruter/09e553a7b66d1a2e68cd5a9ed351c59b
 * Description: Minifies and adds <code>path</code> style data for the <code>twentytwenty-five-style</code> stylesheet so it can be inlined. See <a href="https://core.trac.wordpress.org/ticket/63007">#63007</a>.
 * Requires at least: 6.5
 * Requires PHP: 7.2
 * Version: 0.1.0
 * Author: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * License: GPLv2 or later
 * License URI: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * Update URI: https://gist.github.com/westonruter/09e553a7b66d1a2e68cd5a9ed351c59b
 * GitHub Plugin URI: https://gist.github.com/westonruter/09e553a7b66d1a2e68cd5a9ed351c59b
 *
 * @package TwentyTwentyFiveStylesheetInlining
 */

namespace TwentyTwentyFiveStylesheetInlining;

add_action(
	'wp_enqueue_scripts',
	static function () {
		wp_style_add_data(
			'twentytwentyfive-style',
			'path',
			get_parent_theme_file_path( 'style.css' )
		);
	},
	20
);

function get_theme_style_css(): string {
	static $css = null;
	if ( null !== $css ) {
		return $css;
	}
	$css = file_get_contents( get_parent_theme_file_path( 'style.css' ) ); // 2,505 bytes before minification
	if ( ! SCRIPT_DEBUG ) {
		// Strip out CSS comments, collapse whitespace, and remove unneeded spaces in this specific CSS file.
		// This works for TT5's theme CSS, but it is not a complete solution applicable to any stylesheet.
		// For a general solution, a proper CSS tokenizer should be used. Alternatively, the CSS should go a build step so that there is a style.min.css minified version available!
		$css = trim( preg_replace( '#/\*.*?\*/\s*#s', '', $css ) );
		$css = preg_replace( '/\s+/', ' ', $css );
		$css = preg_replace( '/(?<=[{};:,+]) | (?=[{};:,!+])/', '', $css );
		$css = str_replace( ';}', '}', $css );
		// 586 bytes after minification
	}
	return $css;
}

add_filter(
	'pre_wp_filesize',
	static function ( $size, $path ) {
		if ( get_parent_theme_file_path( 'style.css' ) === $path ) {
			$size = strlen( get_theme_style_css() );
		}
		return $size;
	},
	10,
	2
);

add_action(
	'wp_head',
	static function () {
		$style = wp_styles()->query( 'twentytwentyfive-style' );

		if ( $style && $style->src === false ) {
			$style->extra['after'][0] = get_theme_style_css();
		}
	},
	2
);