Map nav menu locations on theme switch

This will send nav menu locations through three levels of mapping:
1. If both themes have only one location, that gets mapped.
2. If both themes have locations with the same slug, they get mapped.
3. Locations that (even partially) match slugs from a similar kind of menu location will get mapped.

Menu locations are mapped for Live Previews in the Customizer and during theme switches.

Props westonruter, obenland, welcher, melchoyce.
Fixes #39692.


Built from https://develop.svn.wordpress.org/trunk@41237


git-svn-id: http://core.svn.wordpress.org/trunk@41077 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-customize-nav-menus.php

@@ -27,12 +27,12 @@ final class WP_Customize_Nav_Menus {
 	public $manager;
 
 	/**
-	 * Previewed Menus.
+	 * Original nav menu locations before the theme was switched.
 	 *
-	 * @since 4.3.0
+	 * @since 4.9.0
 	 * @var array
 	 */
-	public $previewed_menus;
+	protected $original_nav_menu_locations;
 
 	/**
 	 * Constructor.
@@ -42,8 +42,8 @@ final class WP_Customize_Nav_Menus {
 	 * @param object $manager An instance of the WP_Customize_Manager class.
 	 */
 	public function __construct( $manager ) {
-		$this->previewed_menus = array();
-		$this->manager         = $manager;
+		$this->manager = $manager;
+		$this->original_nav_menu_locations = get_nav_menu_locations();
 
 		// See https://github.com/xwp/wp-customize-snapshots/blob/962586659688a5b1fd9ae93618b7ce2d4e7a421c/php/class-customize-snapshot-manager.php#L469-L499
 		add_action( 'customize_register', array( $this, 'customize_register' ), 11 );
@@ -582,6 +582,12 @@ final class WP_Customize_Nav_Menus {
 			$choices[ $menu->term_id ] = wp_html_excerpt( $menu->name, 40, '…' );
 		}
 
+		// Attempt to re-map the nav menu location assignments when previewing a theme switch.
+		$mapped_nav_menu_locations = array();
+		if ( ! $this->manager->is_theme_active() ) {
+			$mapped_nav_menu_locations = wp_map_nav_menu_locations( get_nav_menu_locations(), $this->original_nav_menu_locations );
+		}
+
 		foreach ( $locations as $location => $description ) {
 			$setting_id = "nav_menu_locations[{$location}]";
 
@@ -600,6 +606,11 @@ final class WP_Customize_Nav_Menus {
 				) );
 			}
 
+			// Override the assigned nav menu location if mapped during previewed theme switch.
+			if ( isset( $mapped_nav_menu_locations[ $location ] ) ) {
+				$this->manager->set_post_value( $setting_id, $mapped_nav_menu_locations[ $location ] );
+			}
+
 			$this->manager->add_control( new WP_Customize_Nav_Menu_Location_Control( $this->manager, $setting_id, array(
 				'label'       => $description,
 				'location_id' => $location,

wp-includes/default-filters.php

@@ -262,6 +262,7 @@ add_action( 'wp_footer',           'wp_print_footer_scripts',         20    );
 add_action( 'template_redirect',   'wp_shortlink_header',             11, 0 );
 add_action( 'wp_print_footer_scripts', '_wp_footer_scripts'                 );
 add_action( 'init',                'check_theme_switched',            99    );
+add_action( 'after_switch_theme',  '_wp_menus_changed'                      );
 add_action( 'after_switch_theme',  '_wp_sidebars_changed'                   );
 add_action( 'wp_print_styles',     'print_emoji_styles'                     );
 

wp-includes/nav-menu.php

@@ -1026,3 +1026,111 @@ function _wp_delete_customize_changeset_dependent_auto_drafts( $post_id ) {
 	}
 	add_action( 'delete_post', '_wp_delete_customize_changeset_dependent_auto_drafts' );
 }
+
+/**
+ * Handle menu config after theme change.
+ *
+ * @access private
+ * @since 4.9.0
+ */
+function _wp_menus_changed() {
+	$old_nav_menu_locations    = get_option( 'theme_switch_menu_locations', array() );
+	$new_nav_menu_locations    = get_nav_menu_locations();
+	$mapped_nav_menu_locations = wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations );
+
+	set_theme_mod( 'nav_menu_locations', $mapped_nav_menu_locations );
+	delete_option( 'theme_switch_menu_locations' );
+}
+
+/**
+ * Maps nav menu locations according to assignments in previously active theme.
+ *
+ * @since 4.9.0
+ *
+ * @param array $new_nav_menu_locations New nav menu locations assignments.
+ * @param array $old_nav_menu_locations Old nav menu locations assignments.
+ * @return array Nav menus mapped to new nav menu locations.
+ */
+function wp_map_nav_menu_locations( $new_nav_menu_locations, $old_nav_menu_locations ) {
+	$registered_nav_menus = get_registered_nav_menus();
+
+	// Short-circuit if there are no old nav menu location assignments to map.
+	if ( empty( $old_nav_menu_locations ) ) {
+		return $new_nav_menu_locations;
+	}
+
+	// If old and new theme have just one location, map it and we're done.
+	if ( 1 === count( $old_nav_menu_locations ) && 1 === count( $registered_nav_menus ) ) {
+		$new_nav_menu_locations[ key( $registered_nav_menus ) ] = array_pop( $old_nav_menu_locations );
+		return $new_nav_menu_locations;
+	}
+
+	$old_locations = array_keys( $old_nav_menu_locations );
+
+	// Map locations with the same slug.
+	foreach ( $registered_nav_menus as $location => $name ) {
+		if ( in_array( $location, $old_locations, true ) ) {
+			$new_nav_menu_locations[ $location ] = $old_nav_menu_locations[ $location ];
+			unset( $old_nav_menu_locations[ $location ] );
+		}
+	}
+
+	// If there are no old nav menu locations left, then we're done.
+	if ( empty( $old_nav_menu_locations ) ) {
+		return $new_nav_menu_locations;
+	}
+
+	/*
+	 * If old and new theme both have locations that contain phrases
+	 * from within the same group, make an educated guess and map it.
+	 */
+	$common_slug_groups = array(
+		array( 'header', 'main', 'navigation', 'primary', 'top' ),
+		array( 'bottom', 'footer', 'secondary', 'subsidiary' ),
+	);
+
+	// Go through each group...
+	foreach ( $common_slug_groups as $slug_group ) {
+
+		// ...and see if any of these slugs...
+		foreach ( $slug_group as $slug ) {
+
+			// ...and any of the new menu locations...
+			foreach ( $registered_nav_menus as $new_location => $name ) {
+
+				// ...actually match!
+				if ( false === stripos( $new_location, $slug ) && false === stripos( $slug, $new_location ) ) {
+					continue;
+				}
+
+				// Then see if any of the old locations...
+				foreach ( $old_nav_menu_locations as $location => $menu_id ) {
+
+					// ...and any slug in the same group...
+					foreach ( $slug_group as $slug ) {
+
+						// ... have a match as well.
+						if ( false === stripos( $location, $slug ) && false === stripos( $slug, $location ) ) {
+							continue;
+						}
+
+						// Make sure this location wasn't mapped and removed previously.
+						if ( ! empty( $old_nav_menu_locations[ $location ] ) ) {
+
+							// We have a match that can be mapped!
+							$new_nav_menu_locations[ $new_location ] = $old_nav_menu_locations[ $location ];
+
+							// Remove the mapped location so it can't be mapped again.
+							unset( $old_nav_menu_locations[ $location ] );
+
+							// Go back and check the next new menu location.
+							continue 3;
+						}
+					} // endforeach ( $slug_group as $slug )
+				} // endforeach ( $old_nav_menu_locations as $location => $menu_id )
+			} // endforeach foreach ( $registered_nav_menus as $new_location => $name )
+		} // endforeach ( $slug_group as $slug )
+	} // endforeach ( $common_slug_groups as $slug_group )
+
+	return $new_nav_menu_locations;
+}

wp-includes/theme.php

@@ -691,6 +691,7 @@ function switch_theme( $stylesheet ) {
 	}
 
 	$nav_menu_locations = get_theme_mod( 'nav_menu_locations' );
+	add_option( 'theme_switch_menu_locations', $nav_menu_locations );
 
 	if ( func_num_args() > 1 ) {
 		$stylesheet = func_get_arg( 1 );
@@ -731,13 +732,6 @@ function switch_theme( $stylesheet ) {
 		if ( 'wp_ajax_customize_save' === current_action() ) {
 			remove_theme_mod( 'sidebars_widgets' );
 		}
-
-		if ( ! empty( $nav_menu_locations ) ) {
-			$nav_mods = get_theme_mod( 'nav_menu_locations' );
-			if ( empty( $nav_mods ) ) {
-				set_theme_mod( 'nav_menu_locations', $nav_menu_locations );
-			}
-		}
 	}
 
 	update_option( 'theme_switched', $old_theme->get_stylesheet() );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.9-alpha-41236';
+$wp_version = '4.9-alpha-41237';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.