Code review for 6.1.1 global stylesheet cache testing plugin

README.md

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+# Test for Trac 56970
+
+Moves global stylesheet from transient to WP_Object_Cache, and resolves an inline CSS issue related to Gallery blocks when upgrading to WordPress 6.1.1. Tested with starting version of 5.9.5 and 6.0.3.
+
+See [Trac 56970](https://core.trac.wordpress.org/ticket/56970) for additional details.
+
+## Purpose
+If testing with this plugin is shown to resolve the issues reported in [Trac 56970](https://core.trac.wordpress.org/ticket/56970), then the [proposed fix](https://github.com/WordPress/wordpress-develop/pull/3712) could be included in a future minor release.
+
+## Installation
+Copy `hotfix-56970.php` to your `wp-content/plugins/` folder, and activate it on the *Plugins > Installed Plugins* screen.
+
+## Testing
+Testing requires starting with a standard WordPress install of version 5.9 through 6.0.3. Steps adapted from [Trac 56970#comment:42](https://core.trac.wordpress.org/ticket/56970#comment:42).
+
+1. Create a new site using WordPress 5.9 through 6.0.3.
+2. Navigate to *Appearance > Themes* and activate **Twenty Twenty-One**.
+3. Navigate to *Settings > Permalinks* and select anything *except for* the "Plain" structure.
+4. Navigate to *Posts > Add New*. Insert a Gallery block and add three images.
+5. Save the post and view it on the frontend. Confirm that the images are displayed in 3 columns.
+6. [Install and activate the test plugin](#installation).
+7. Upgrade the site to WordPress 6.1.1.
+8. View the same post from Step 4, and confirm that it displays the images in 3 columns on the frontend.
+9. Navigate to *Posts > All Posts* and edit the post. Confirm that the images in the block editor are displayed in 3 columns and no errors occur.
+
+## Reporting Issues
+Please open an issue in [this test plugin repository](https://github.com/ironprogrammer/wp-hotfix-56970/issues).

hotfix-56970.php

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 <?php
 /**
- * Plugin Name: Hotfix for Trac 56970
- * Description: Cleans theme.json cache. See <a href="https://core.trac.wordpress.org/ticket/56970">Trac 56970</a>.
+ * Plugin Name: Test for Trac 56970
+ * Description: Moves global stylesheet from transient to WP_Object_Cache. See <a href="https://core.trac.wordpress.org/ticket/56970">Trac 56970</a>.
  * Version: 0.1
  */
 
+// Initialize plugin.
+WP_Hotfix_56970_Controller::init();
+
+class WP_Hotfix_56970_Controller {
+	public static function init() {
+		add_action( 'init', 'wp_hotfix_56970_init' );
+	}
+}
+
+function wp_hotfix_56970_init() {
+	global $wp_version;
+
+	// Issue described in Trac 56970 only affects upgrade from < 6.1 to 6.1.1.
+	if ( '6.1.1' === $wp_version ) {
+		// Unhook default global styles enqueue.
+		remove_action( 'wp_enqueue_scripts', 'wp_enqueue_global_styles' );
+		remove_action( 'wp_footer', 'wp_enqueue_global_styles', 1 );
+
+		// Hook override global styles enqueue.
+		add_action( 'wp_enqueue_scripts', 'wp_hotfix_611_enqueue_global_styles' );
+		add_action( 'wp_footer', 'wp_hotfix_611_enqueue_global_styles', 1 );
+
+		// Hook override for block editor styles.
+		add_filter( 'block_editor_settings_all', 'wp_hotfix_611_get_block_editor_settings', PHP_INT_MAX );
+
+		// Unhook default cache cleaning mechanism.
+		remove_action( 'switch_theme', array( 'WP_Theme_JSON_Resolver', 'clean_cached_data' ) );
+		remove_action( 'start_previewing_theme', array( 'WP_Theme_JSON_Resolver', 'clean_cached_data' ) );
+
+		// Hook override cache cleaning mechanism.
+		add_action( 'switch_theme', 'wp_hotfix_611_wp_clean_theme_json_caches' );
+		add_action( 'start_previewing_theme', 'wp_hotfix_611_wp_clean_theme_json_caches' );
+		add_action( 'plugins_loaded', 'wp_hotfix_611_wp_add_non_persistent_theme_json_cache_group' );
+	}
+}
+
+/**
+ * Override wp_enqueue_global_styles in wp-includes/script-loader.php.
+ *
+ * Enqueues the global styles defined via theme.json.
+ */
+function wp_hotfix_611_enqueue_global_styles() {
+	$separate_assets  = wp_should_load_separate_core_block_assets();
+	$is_block_theme   = wp_is_block_theme();
+	$is_classic_theme = ! $is_block_theme;
+
+	/*
+	 * Global styles should be printed in the head when loading all styles combined.
+	 * The footer should only be used to print global styles for classic themes with separate core assets enabled.
+	 *
+	 * See https://core.trac.wordpress.org/ticket/53494.
+	 */
+	if (
+		( $is_block_theme && doing_action( 'wp_footer' ) ) ||
+		( $is_classic_theme && doing_action( 'wp_footer' ) && ! $separate_assets ) ||
+		( $is_classic_theme && doing_action( 'wp_enqueue_scripts' ) && $separate_assets )
+	) {
+		return;
+	}
+
+	/*
+	 * If loading the CSS for each block separately, then load the theme.json CSS conditionally.
+	 * This removes the CSS from the global-styles stylesheet and adds it to the inline CSS for each block.
+	 * This filter must be registered before calling wp_get_global_stylesheet();
+	 */
+	add_filter( 'wp_theme_json_get_style_nodes', 'wp_filter_out_block_nodes' );
+
+	$stylesheet = wp_hotfix_611_get_global_stylesheet();
+
+	if ( empty( $stylesheet ) ) {
+		return;
+	}
+
+	wp_register_style( 'global-styles', false, array(), true, true );
+	wp_add_inline_style( 'global-styles', $stylesheet );
+	wp_enqueue_style( 'global-styles' );
+
+	// Add each block as an inline css.
+	wp_add_global_styles_for_blocks();
+}
+
+/**
+ * Override wp_get_global_stylesheet in wp-includes/global-styles-and-settings.php.
+ *
+ * Returns the stylesheet resulting of merging core, theme, and user data.
+ *
+ * @param array $types Types of styles to load. Optional.
+ *                     It accepts 'variables', 'styles', 'presets' as values.
+ *                     If empty, it'll load all for themes with theme.json support
+ *                     and only [ 'variables', 'presets' ] for themes without theme.json support.
+ * @return string Stylesheet.
+ */
+function wp_hotfix_611_get_global_stylesheet( $types = array() ) {
+	// Ignore cache when `WP_DEBUG` is enabled, so it doesn't interfere with the theme developers workflow.
+	$can_use_cached = empty( $types ) && ! WP_DEBUG;
+	$cache_key      = 'wp_get_global_stylesheet';
+	$cache_group    = 'theme_json';
+	if ( $can_use_cached ) {
+		$cached = wp_cache_get( $cache_key, $cache_group );
+		if ( $cached ) {
+			return $cached;
+		}
+	}
+	$tree                = WP_Theme_JSON_Resolver::get_merged_data();
+	$supports_theme_json = WP_Theme_JSON_Resolver::theme_has_support();
+	if ( empty( $types ) && ! $supports_theme_json ) {
+		$types = array( 'variables', 'presets', 'base-layout-styles' );
+	} elseif ( empty( $types ) ) {
+		$types = array( 'variables', 'styles', 'presets' );
+	}
+
+	/*
+	 * If variables are part of the stylesheet, then add them.
+	 * This is so themes without a theme.json still work as before 5.9:
+	 * they can override the default presets.
+	 * See https://core.trac.wordpress.org/ticket/54782
+	 */
+	$styles_variables = '';
+	if ( in_array( 'variables', $types, true ) ) {
+		/*
+		 * Only use the default, theme, and custom origins. Why?
+		 * Because styles for `blocks` origin are added at a later phase
+		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
+		 * @see wp_add_global_styles_for_blocks
+		 */
+		$origins          = array( 'default', 'theme', 'custom' );
+		$styles_variables = $tree->get_stylesheet( array( 'variables' ), $origins );
+		$types            = array_diff( $types, array( 'variables' ) );
+	}
+
+	/*
+	 * For the remaining types (presets, styles), we do consider origins:
+	 *
+	 * - themes without theme.json: only the classes for the presets defined by core
+	 * - themes with theme.json: the presets and styles classes, both from core and the theme
+	 */
+	$styles_rest = '';
+	if ( ! empty( $types ) ) {
+		/*
+		 * Only use the default, theme, and custom origins. Why?
+		 * Because styles for `blocks` origin are added at a later phase
+		 * (i.e. in the render cycle). Here, only the ones in use are rendered.
+		 * @see wp_add_global_styles_for_blocks
+		 */
+		$origins = array( 'default', 'theme', 'custom' );
+		if ( ! $supports_theme_json ) {
+			$origins = array( 'default' );
+		}
+		$styles_rest = $tree->get_stylesheet( $types, $origins );
+	}
+	$stylesheet = $styles_variables . $styles_rest;
+	if ( $can_use_cached ) {
+		wp_cache_set( $cache_key, $stylesheet, $cache_group );
+	}
+	return $stylesheet;
+}
+
+/**
+ * Add styles to the block editor settings.
+ *
+ * @param array $settings Existing block editor settings.
+ * @return array New block editor settings.
+ */
+function wp_hotfix_611_get_block_editor_settings( $settings ) {
+	// Recreate global styles.
+	$new_global_styles = array();
+	$presets           = array(
+		array(
+			'css'            => 'variables',
+			'__unstableType' => 'presets',
+			'isGlobalStyles' => true,
+		),
+		array(
+			'css'            => 'presets',
+			'__unstableType' => 'presets',
+			'isGlobalStyles' => true,
+		),
+	);
+	foreach ( $presets as $preset_style ) {
+		$actual_css = wp_hotfix_611_get_global_stylesheet( array( $preset_style['css'] ) );
+		if ( '' !== $actual_css ) {
+			$preset_style['css'] = $actual_css;
+			$new_global_styles[] = $preset_style;
+		}
+	}
+
+	if ( WP_Theme_JSON_Resolver::theme_has_support() ) {
+		$block_classes = array(
+			'css'            => 'styles',
+			'__unstableType' => 'theme',
+			'isGlobalStyles' => true,
+		);
+	} else {
+		// If there is no `theme.json` file, ensure base layout styles are still available.
+		$block_classes = array(
+			'css'            => 'base-layout-styles',
+			'__unstableType' => 'base-layout',
+			'isGlobalStyles' => true,
+		);
+	}
+	$styles_css = wp_hotfix_611_get_global_stylesheet( array( $block_classes['css'] ) );
+	if ( '' !== $styles_css ) {
+		$block_classes['css'] = $styles_css;
+		$new_global_styles[]  = $block_classes;
+	}
+
+	$settings['styles'] = array_merge( $new_global_styles, get_block_editor_theme_styles() );
+
+	return $settings;
+}
+
+/**
+ * Clean the caches under the theme_json group.
+ */
+function wp_hotfix_611_wp_clean_theme_json_caches() {
+	wp_cache_delete( 'wp_get_global_stylesheet', 'theme_json' );
+	WP_Theme_JSON_Resolver::clean_cached_data();
+}
+
+/**
+ * Tell cache mechanisms not to persist theme.json data across requests for data
+ * stored under the wp_get_global_stylesheet cache group.
+ */
+function wp_hotfix_611_wp_add_non_persistent_theme_json_cache_group() {
+	wp_cache_add_non_persistent_groups( 'theme_json' );
+}