Plugin: Compatibility fixes for WP 5.9 and Site Editor (#42549)

lib/compat/wordpress-6.0/site-editor.php

@@ -0,0 +1,95 @@
+<?php
+/**
+ * Compatibility fixes for WP 5.9 and Site Editor.
+ *
+ * It can be removed after the minimum required WP version is 6.0
+ *
+ * @package WordPress
+ */
+
+/**
+ * Return the correct template for the site's home page.
+ *
+ * @access private
+ * @since 6.0.0
+ *
+ * @return array|null A template object, or null if none could be found
+ */
+function gutenberg_resolve_home_template() {
+	$show_on_front = get_option( 'show_on_front' );
+	$front_page_id = get_option( 'page_on_front' );
+
+	if ( 'page' === $show_on_front && $front_page_id ) {
+		return array(
+			'postType' => 'page',
+			'postId'   => $front_page_id,
+		);
+	}
+
+	$hierarchy = array( 'front-page', 'home', 'index' );
+	$template  = resolve_block_template( 'home', $hierarchy, '' );
+
+	if ( ! $template ) {
+		return null;
+	}
+
+	return array(
+		'postType' => 'wp_template',
+		'postId'   => $template->id,
+	);
+}
+
+/**
+ * Do a server-side redirection if missing `postType` and `postId`
+ * query args when visiting site editor.
+ *
+ * Note: This is a backward compatibility redirect for WP 5.9.
+ *
+ * @return void
+ */
+function gutenberg_site_editor_maybe_redirect() {
+	// Skip redirection for WP 6.0 and later.
+	if ( function_exists( '_resolve_home_block_template' ) ) {
+		return;
+	}
+
+	// Check theme support. The action runs before checks in the Site Editor.
+	if ( ! wp_is_block_theme() ) {
+		return;
+	}
+
+	if ( empty( $_GET['postType'] ) && empty( $_GET['postId'] ) ) {
+		$template = gutenberg_resolve_home_template();
+		if ( ! empty( $_GET['styles'] ) ) {
+			$template['styles'] = sanitize_key( $_GET['styles'] );
+		}
+
+		$redirect_url = add_query_arg(
+			$template,
+			admin_url( 'site-editor.php' )
+		);
+		wp_safe_redirect( $redirect_url );
+		exit;
+	}
+}
+add_action( 'load-site-editor.php', 'gutenberg_site_editor_maybe_redirect' );
+
+/**
+ * Add home template settings for WP 5.9.
+ *
+ * @param array                   $settings Existing block editor settings.
+ * @param WP_Block_Editor_Context $context The current block editor context.
+ * @return array
+ */
+function gutenberg_site_editor_homepage_setting( $settings, $context ) {
+	if ( isset( $context->post ) ) {
+		return $settings;
+	}
+
+	if ( ! isset( $settings['__unstableHomeTemplate'] ) ) {
+		$settings['__unstableHomeTemplate'] = gutenberg_resolve_home_template();
+	}
+
+	return $settings;
+}
+add_filter( 'block_editor_settings_all', 'gutenberg_site_editor_homepage_setting', 10, 2 );

lib/load.php

@@ -70,7 +70,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 require __DIR__ . '/compat/wordpress-6.0/class-wp-theme-json-6-0.php';
 require __DIR__ . '/compat/wordpress-6.0/class-wp-theme-json-resolver-6-0.php';
 require __DIR__ . '/compat/wordpress-6.0/block-patterns.php';
-require __DIR__ . '/compat/wordpress-6.0/block-template.php';
+require __DIR__ . '/compat/wordpress-6.0/site-editor.php';
 require __DIR__ . '/compat/wordpress-6.0/edit-form-blocks.php';
 require __DIR__ . '/compat/wordpress-6.0/block-patterns-update.php';
 require __DIR__ . '/compat/wordpress-6.0/client-assets.php';