How to determine if WP_Customize_Nav_Menu_Item_Setting is a 'taxonomy' type?

Question

I'm following the answer given for Add settings to menu items in the Customizer.

I'd like to inspect if a menu item is of type taxonomy. However, get_post_type returns nav_menu_item. How do I dig deeper?

    function customize_save_after($wp_customize)
    {
        foreach ( $wp_customize->settings() as $setting ) {
            if ( $setting instanceof WP_Customize_Nav_Menu_Item_Setting ) {
                $type = get_post_type($setting->post_id); // Returns 'nav_menu_item'.
                // How to retrieve the underlying type?
                $underlying_type = ....?

                if ($underlying_type !== 'taxonomy')
                {
                    return;
                }

                update_post_meta( $setting->post_id, '_my-custom-setting-field', (!empty( $setting->my_custom_setting_field) ) );
            }
        }
    }

Answer 1

It's easy to get the type of the menu item.

Just call the setting's value() method, which in the case of a nav menu item, would return an array with items like type (sample value: post_type or taxonomy) and object (sample value: post, page or category).

So in your case, just check whether the type's value is taxonomy.

$value           = $setting->value();
$underlying_type = is_array( $value ) ? $value['type'] : '';

/* Sample dump output of the $value array:
Array
(
    [menu_item_parent] => 0
    [object_id] => 1
    [object] => category
    [type] => taxonomy
    [type_label] => Category
    [url] => https://example.com/category/uncategorized/
    [title] => 
    [target] => 
    [attr_title] => 
    [description] => 
    [classes] => 
    [xfn] => 
    [position] => 3
    [status] => publish
    [original_title] => Uncategorized
    [nav_menu_term_id] => 89
    [_invalid] => 
)
*/

Answer 2

After going over the referenced question again, I noticed that some code was not pasted in the answer that was shared in the github gist. The way to access the values is:

$unsanitized_post_value = $setting->manager->unsanitized_post_values()[ $setting->id ];