Change context depending on user caps to prevent clientside request i…

…n post editor.

Sync with #66543

lib/compat/wordpress-6.6/rest-api.php

@@ -197,3 +197,20 @@ function gutenberg_register_wp_rest_post_types_controller_fields() {
 	);
 }
 add_action( 'rest_api_init', 'gutenberg_register_wp_rest_post_types_controller_fields' );
+
+/**
+ * Preload theme and global styles paths to avoid flash of variation styles in post editor.
+ *
+ * @param array                   $paths REST API paths to preload.
+ * @param WP_Block_Editor_Context $context Current block editor context.
+ * @return array Filtered preload paths.
+ */
+function gutenberg_block_editor_preload_paths_6_6( $paths, $context ) {
+	if ( 'core/edit-post' === $context->name ) {
+		$paths[] = '/wp/v2/global-styles/themes/' . get_stylesheet();
+		$paths[] = '/wp/v2/themes?context=edit&status=active';
+		$paths[] = '/wp/v2/global-styles/' . WP_Theme_JSON_Resolver_Gutenberg::get_user_global_styles_post_id() . '?context=edit';
+	}
+	return $paths;
+}
+add_filter( 'block_editor_rest_api_preload_paths', 'gutenberg_block_editor_preload_paths_6_6', 10, 2 );

lib/compat/wordpress-6.7/rest-api.php

@@ -51,9 +51,9 @@ function gutenberg_block_editor_preload_paths_6_7( $paths, $context ) {
 	}
 
 	// Preload theme and global styles paths.
-	$excluded_paths = array();
 	if ( 'core/edit-site' === $context->name || 'core/edit-post' === $context->name ) {
 		$active_theme     = get_stylesheet();
+		$excluded_paths   = array();
 		$global_styles_id = WP_Theme_JSON_Resolver_Gutenberg::get_user_global_styles_post_id();
 		$paths[]          = '/wp/v2/global-styles/themes/' . $active_theme . '?context=view';
 		$paths[]          = '/wp/v2/global-styles/themes/' . $active_theme . '/variations?context=view';

lib/compat/wordpress-6.8/rest-api.php

@@ -0,0 +1,50 @@
+<?php
+/**
+ * PHP and WordPress configuration compatibility functions for the Gutenberg
+ * editor plugin changes related to REST API.
+ *
+ * @package gutenberg
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	die( 'Silence is golden.' );
+}
+
+/**
+ * Update the preload paths registered in Core (`site-editor.php` or `edit-form-blocks.php`).
+ *
+ * @param array                   $paths REST API paths to preload.
+ * @param WP_Block_Editor_Context $context Current block editor context.
+ * @return array Filtered preload paths.
+ */
+function gutenberg_block_editor_preload_paths_6_8( $paths, $context ) {
+	// Preload theme and global styles paths.
+	if ( 'core/edit-site' === $context->name || 'core/edit-post' === $context->name ) {
+		$excluded_paths   = array();
+		$global_styles_id = WP_Theme_JSON_Resolver_Gutenberg::get_user_global_styles_post_id();
+
+		/*
+		 * Removes any edit or view context paths originating from Core,
+		 * or elsewhere, e.g., gutenberg_block_editor_preload_paths_6_6().
+		 * This also ensures there no duplicates. block_editor_rest_api_preload() does
+		 * not dedupe, and will render request output into the HTML for all provided paths.
+		 */
+		$excluded_paths[] = '/wp/v2/global-styles/' . $global_styles_id . '?context=view';
+		// Removes any edit context path originating from gutenberg_block_editor_preload_paths_6_6().
+		$excluded_paths[] = '/wp/v2/global-styles/' . $global_styles_id . '?context=edit';
+		foreach ( $paths as $key => $path ) {
+			if ( in_array( $path, $excluded_paths, true ) ) {
+				unset( $paths[ $key ] );
+			}
+		}
+
+		/*
+		 * Now add the global styles path with the correct context based on user caps.
+		 */
+		$context = current_user_can( 'edit_theme_options' ) ? 'edit' : 'view';
+		$paths[] = "/wp/v2/global-styles/$global_styles_id?context=$context";
+	}
+
+	return $paths;
+}
+add_filter( 'block_editor_rest_api_preload_paths', 'gutenberg_block_editor_preload_paths_6_8', 10, 2 );

lib/load.php

@@ -47,6 +47,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 	require __DIR__ . '/compat/wordpress-6.7/rest-api.php';
 
 	// WordPress 6.8 compat.
+	require __DIR__ . '/compat/wordpress-6.8/rest-api.php';
 	require __DIR__ . '/compat/wordpress-6.8/block-comments.php';
 	require __DIR__ . '/compat/wordpress-6.8/class-gutenberg-rest-comment-controller-6-8.php';