From ae515caebf6f56fc7d5bbdd65e8140f70bd04288 Mon Sep 17 00:00:00 2001
From: Felix Arntz <felix-arntz@leaves-and-love.net>
Date: Tue, 20 Jun 2023 17:54:19 +0000
Subject: [PATCH] Editor: Introduce `WP_Theme_JSON::prepend_to_selector()` to
 improve code quality and performance.

The `WP_Theme_JSON::append_to_selector()` method was previously used for both appending and prepending which violated the single responsibility principle. It resulted in additional conditionals which also came at a performance cost, particularly because the method is called over 1,000 times during a regular WordPress request.

With the new `WP_Theme_JSON::prepend_to_selector()` method, there are now two distinct methods for the two distinct purposes. The now useless third parameter on `WP_Theme_JSON::append_to_selector()` has been removed (rather than deprecated), which is acceptable given that it is a protected method on a class that is not intended for extensions.

Props bor0, costdev, flixos90, isabel_brison, oandregal, spacedmonkey.
Fixes #58193.
See #58457.

Built from https://develop.svn.wordpress.org/trunk@55950


git-svn-id: http://core.svn.wordpress.org/trunk@55462 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/class-wp-theme-json.php | 46 +++++++++++++++++++++++------
 wp-includes/version.php             |  2 +-
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/wp-includes/class-wp-theme-json.php b/wp-includes/class-wp-theme-json.php
index 6b21f343b1..74f3971bf2 100644
--- a/wp-includes/class-wp-theme-json.php
+++ b/wp-includes/class-wp-theme-json.php
@@ -795,20 +795,45 @@ class WP_Theme_JSON {
 	 *
 	 * @since 5.8.0
 	 * @since 6.1.0 Added append position.
+	 * @since 6.3.0 Removed append position parameter.
 	 *
 	 * @param string $selector  Original selector.
 	 * @param string $to_append Selector to append.
-	 * @param string $position  A position sub-selector should be appended. Default 'right'.
 	 * @return string The new selector.
 	 */
-	protected static function append_to_selector( $selector, $to_append, $position = 'right' ) {
+	protected static function append_to_selector( $selector, $to_append ) {
 		if ( ! str_contains( $selector, ',' ) ) {
-			return 'right' === $position ? $selector . $to_append : $to_append . $selector;
+			return $selector . $to_append;
 		}
 		$new_selectors = array();
 		$selectors     = explode( ',', $selector );
 		foreach ( $selectors as $sel ) {
-			$new_selectors[] = 'right' === $position ? $sel . $to_append : $to_append . $sel;
+			$new_selectors[] = $sel . $to_append;
+		}
+		return implode( ',', $new_selectors );
+	}
+
+	/**
+	 * Prepends a sub-selector to an existing one.
+	 *
+	 * Given the compounded $selector "h1, h2, h3"
+	 * and the $to_prepend selector ".some-class " the result will be
+	 * ".some-class h1, .some-class  h2, .some-class  h3".
+	 *
+	 * @since 6.3.0
+	 *
+	 * @param string $selector   Original selector.
+	 * @param string $to_prepend Selector to prepend.
+	 * @return string The new selector.
+	 */
+	protected static function prepend_to_selector( $selector, $to_prepend ) {
+		if ( ! str_contains( $selector, ',' ) ) {
+			return $to_prepend . $selector;
+		}
+		$new_selectors = array();
+		$selectors     = explode( ',', $selector );
+		foreach ( $selectors as $sel ) {
+			$new_selectors[] = $to_prepend . $sel;
 		}
 		return implode( ',', $new_selectors );
 	}
@@ -900,7 +925,7 @@ class WP_Theme_JSON {
 						$element_selector = array( $el_selector );
 						break;
 					}
-					$element_selector[] = static::append_to_selector( $el_selector, $selector . ' ', 'left' );
+					$element_selector[] = static::prepend_to_selector( $el_selector, $selector . ' ' );
 				}
 				static::$blocks_metadata[ $block_name ]['elements'][ $el_name ] = implode( ',', $element_selector );
 			}
@@ -1537,10 +1562,13 @@ class WP_Theme_JSON {
 			$slugs = static::get_settings_slugs( $settings, $preset_metadata, $origins );
 			foreach ( $preset_metadata['classes'] as $class => $property ) {
 				foreach ( $slugs as $slug ) {
-					$css_var     = static::replace_slug_in_string( $preset_metadata['css_vars'], $slug );
-					$class_name  = static::replace_slug_in_string( $class, $slug );
-					$stylesheet .= static::to_ruleset(
-						static::append_to_selector( $selector, $class_name ),
+					$css_var    = static::replace_slug_in_string( $preset_metadata['css_vars'], $slug );
+					$class_name = static::replace_slug_in_string( $class, $slug );
+
+					// $selector is often empty, so we can save ourselves the `append_to_selector()` call then.
+					$new_selector = '' === $selector ? $class_name : static::append_to_selector( $selector, $class_name );
+					$stylesheet  .= static::to_ruleset(
+						$new_selector,
 						array(
 							array(
 								'name'  => $property,
diff --git a/wp-includes/version.php b/wp-includes/version.php
index fb601e3fd6..6ffd42b459 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.3-alpha-55949';
+$wp_version = '6.3-alpha-55950';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.