Backport to WP 6.3 - Navigation fallbacks from 4648

src/wp-includes/class-wp-classic-to-block-menu-converter.php

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+<?php
+/**
+ * WP_Classic_To_Block_Menu_Converter class
+ *
+ * @package WordPress
+ * @since 6.3.0
+ */
+
+/**
+ * Converts a Classic Menu to Block Menu blocks.
+ *
+ * @since 6.3.0.
+ * @access public
+ */
+class WP_Classic_To_Block_Menu_Converter {
+
+	/**
+	 * Converts a Classic Menu to blocks.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @param WP_Term $menu The Menu term object of the menu to convert.
+	 * @return string the serialized and normalized parsed blocks.
+	 */
+	public static function convert( $menu ) {
+
+		if ( ! is_nav_menu( $menu ) ) {
+			return new WP_Error(
+				'invalid_menu',
+				__( 'The menu provided is not a valid menu.' )
+			);
+		}
+
+		$menu_items = wp_get_nav_menu_items( $menu->term_id, array( 'update_post_term_cache' => false ) );
+
+		if ( empty( $menu_items ) ) {
+			return array();
+		}
+
+		// Set up the $menu_item variables.
+		// Adds the class property classes for the current context, if applicable.
+		_wp_menu_item_classes_by_context( $menu_items );
+
+		$menu_items_by_parent_id = static::group_by_parent_id( $menu_items );
+
+		$first_menu_item = isset( $menu_items_by_parent_id[0] )
+			? $menu_items_by_parent_id[0]
+			: array();
+
+		$inner_blocks = static::to_blocks(
+			$first_menu_item,
+			$menu_items_by_parent_id
+		);
+
+		return serialize_blocks( $inner_blocks );
+	}
+
+	/**
+	 * Returns an array of menu items grouped by the id of the parent menu item.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @param array $menu_items An array of menu items.
+	 * @return array
+	 */
+	private static function group_by_parent_id( $menu_items ) {
+		$menu_items_by_parent_id = array();
+
+		foreach ( $menu_items as $menu_item ) {
+			$menu_items_by_parent_id[ $menu_item->menu_item_parent ][] = $menu_item;
+		}
+
+		return $menu_items_by_parent_id;
+	}
+
+	/**
+	 * Turns menu item data into a nested array of parsed blocks
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @param array $menu_items               An array of menu items that represent
+	 *                                        an individual level of a menu.
+	 * @param array $menu_items_by_parent_id  An array keyed by the id of the
+	 *                                        parent menu where each element is an
+	 *                                        array of menu items that belong to
+	 *                                        that parent.
+	 * @return array An array of parsed block data.
+	 */
+	private static function to_blocks( $menu_items, $menu_items_by_parent_id ) {
+
+		if ( empty( $menu_items ) ) {
+			return array();
+		}
+
+		$blocks = array();
+
+		foreach ( $menu_items as $menu_item ) {
+			$class_name       = ! empty( $menu_item->classes ) ? implode( ' ', (array) $menu_item->classes ) : null;
+			$id               = ( null !== $menu_item->object_id && 'custom' !== $menu_item->object ) ? $menu_item->object_id : null;
+			$opens_in_new_tab = null !== $menu_item->target && '_blank' === $menu_item->target;
+			$rel              = ( null !== $menu_item->xfn && '' !== $menu_item->xfn ) ? $menu_item->xfn : null;
+			$kind             = null !== $menu_item->type ? str_replace( '_', '-', $menu_item->type ) : 'custom';
+
+			$block = array(
+				'blockName' => isset( $menu_items_by_parent_id[ $menu_item->ID ] ) ? 'core/navigation-submenu' : 'core/navigation-link',
+				'attrs'     => array(
+					'className'     => $class_name,
+					'description'   => $menu_item->description,
+					'id'            => $id,
+					'kind'          => $kind,
+					'label'         => $menu_item->title,
+					'opensInNewTab' => $opens_in_new_tab,
+					'rel'           => $rel,
+					'title'         => $menu_item->attr_title,
+					'type'          => $menu_item->object,
+					'url'           => $menu_item->url,
+				),
+			);
+
+			$block['innerBlocks']  = isset( $menu_items_by_parent_id[ $menu_item->ID ] )
+			? static::to_blocks( $menu_items_by_parent_id[ $menu_item->ID ], $menu_items_by_parent_id )
+			: array();
+			$block['innerContent'] = array_map( 'serialize_block', $block['innerBlocks'] );
+
+			$blocks[] = $block;
+		}
+
+		return $blocks;
+	}
+}

src/wp-includes/class-wp-navigation-fallback.php

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+<?php
+/**
+ * WP_Navigation_Fallback class
+ *
+ * Manages fallback behavior for Navigation menus.
+ *
+ * @package WordPress
+ * @subpackage Navigation
+ * @since 6.3.0
+ */
+
+/**
+ * Manages fallback behavior for Navigation menus.
+ *
+ * @access public
+ * @since 6.3.0.
+ */
+class WP_Navigation_Fallback {
+
+	/**
+	 * Gets (and/or creates) an appropriate fallback Navigation Menu.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return WP_Post|null the fallback Navigation Post or null.
+	 */
+	public static function get_fallback() {
+
+		$fallback = static::get_most_recently_published_navigation();
+
+		if ( $fallback ) {
+			return $fallback;
+		}
+
+		$fallback = static::create_classic_menu_fallback();
+
+		if ( $fallback && ! is_wp_error( $fallback ) ) {
+			// Return the newly created fallback post object which will now be the most recently created navigation menu.
+			return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
+		}
+
+		$fallback = static::create_default_fallback();
+
+		if ( $fallback && ! is_wp_error( $fallback ) ) {
+			// Return the newly created fallback post object which will now be the most recently created navigation menu.
+			return $fallback instanceof WP_Post ? $fallback : static::get_most_recently_published_navigation();
+		}
+
+		return null;
+	}
+
+	/**
+	 * Finds the most recently published `wp_navigation` post type.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return WP_Post|null the first non-empty Navigation or null.
+	 */
+	private static function get_most_recently_published_navigation() {
+
+		$parsed_args = array(
+			'post_type'              => 'wp_navigation',
+			'no_found_rows'          => true,
+			'update_post_meta_cache' => false,
+			'update_post_term_cache' => false,
+			'order'                  => 'DESC',
+			'orderby'                => 'date',
+			'post_status'            => 'publish',
+			'posts_per_page'         => 1,
+		);
+
+		$navigation_post = new WP_Query( $parsed_args );
+
+		if ( count( $navigation_post->posts ) > 0 ) {
+			return $navigation_post->posts[0];
+		}
+
+		return null;
+	}
+
+	/**
+	 * Creates a Navigation Menu post from a Classic Menu.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return int|WP_Error The post ID of the default fallback menu or a WP_Error object.
+	 */
+	private static function create_classic_menu_fallback() {
+		// See if we have a classic menu.
+		$classic_nav_menu = static::get_fallback_classic_menu();
+
+		if ( ! $classic_nav_menu ) {
+			return new WP_Error( 'no_classic_menus', __( 'No Classic Menus found.' ) );
+		}
+
+		// If there is a classic menu then convert it to blocks.
+		$classic_nav_menu_blocks = WP_Classic_To_Block_Menu_Converter::convert( $classic_nav_menu );
+
+		if ( empty( $classic_nav_menu_blocks ) ) {
+			return new WP_Error( 'cannot_convert_classic_menu', __( 'Unable to convert Classic Menu to blocks.' ) );
+		}
+
+		// Create a new navigation menu from the classic menu.
+		$classic_menu_fallback = wp_insert_post(
+			array(
+				'post_content' => $classic_nav_menu_blocks,
+				'post_title'   => $classic_nav_menu->name,
+				'post_name'    => $classic_nav_menu->slug,
+				'post_status'  => 'publish',
+				'post_type'    => 'wp_navigation',
+			),
+			true // So that we can check whether the result is an error.
+		);
+
+		return $classic_menu_fallback;
+	}
+
+	/**
+	 * Determine the most appropriate classic navigation menu to use as a fallback.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return WP_Term|null The most appropriate classic navigation menu to use as a fallback.
+	 */
+	private static function get_fallback_classic_menu() {
+		$classic_nav_menus = wp_get_nav_menus();
+
+		if ( ! $classic_nav_menus || is_wp_error( $classic_nav_menus ) ) {
+			return null;
+		}
+
+		$nav_menu = static::get_nav_menu_at_primary_location();
+
+		if ( $nav_menu ) {
+			return $nav_menu;
+		}
+
+		$nav_menu = static::get_nav_menu_with_primary_slug( $classic_nav_menus );
+
+		if ( $nav_menu ) {
+			return $nav_menu;
+		}
+
+		return static::get_most_recently_created_nav_menu( $classic_nav_menus );
+	}
+
+
+	/**
+	 * Sorts the classic menus and returns the most recently created one.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @param WP_Term[] $classic_nav_menus Array of classic nav menu term objects.
+	 * @return WP_Term The most recently created classic nav menu.
+	 */
+	private static function get_most_recently_created_nav_menu( $classic_nav_menus ) {
+		usort(
+			$classic_nav_menus,
+			static function( $a, $b ) {
+				return $b->term_id - $a->term_id;
+			}
+		);
+
+		return $classic_nav_menus[0];
+	}
+
+	/**
+	 * Returns the classic menu with the slug `primary` if it exists.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @param WP_Term[] $classic_nav_menus Array of classic nav menu term objects.
+	 * @return WP_Term|null The classic nav menu with the slug `primary` or null.
+	 */
+	private static function get_nav_menu_with_primary_slug( $classic_nav_menus ) {
+		foreach ( $classic_nav_menus as $classic_nav_menu ) {
+			if ( 'primary' === $classic_nav_menu->slug ) {
+				return $classic_nav_menu;
+			}
+		}
+
+		return null;
+	}
+
+
+	/**
+	 * Gets the classic menu assigned to the `primary` navigation menu location
+	 * if it exists.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return WP_Term|null The classic nav menu assigned to the `primary` location or null.
+	 */
+	private static function get_nav_menu_at_primary_location() {
+		$locations = get_nav_menu_locations();
+
+		if ( isset( $locations['primary'] ) ) {
+			$primary_menu = wp_get_nav_menu_object( $locations['primary'] );
+
+			if ( $primary_menu ) {
+				return $primary_menu;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * Creates a default Navigation Block Menu fallback.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return int|WP_Error The post ID of the default fallback menu or a WP_Error object.
+	 */
+	private static function create_default_fallback() {
+
+		$default_blocks = static::get_default_fallback_blocks();
+
+		// Create a new navigation menu from the fallback blocks.
+		$default_fallback = wp_insert_post(
+			array(
+				'post_content' => $default_blocks,
+				'post_title'   => _x( 'Navigation', 'Title of a Navigation menu' ),
+				'post_name'    => 'navigation',
+				'post_status'  => 'publish',
+				'post_type'    => 'wp_navigation',
+			),
+			true // So that we can check whether the result is an error.
+		);
+
+		return $default_fallback;
+	}
+
+	/**
+	 * Gets the rendered markup for the default fallback blocks.
+	 *
+	 * @since 6.3.0.
+	 *
+	 * @return string default blocks markup to use a the fallback.
+	 */
+	private static function get_default_fallback_blocks() {
+		$registry = WP_Block_Type_Registry::get_instance();
+
+		// If `core/page-list` is not registered then use empty blocks.
+		return $registry->is_registered( 'core/page-list' ) ? '<!-- wp:page-list /-->' : '';
+	}
+}