Change the user role on purchase in WooCommerce

change-the-user-role-on-purchase-in-woocommerce.php

add_action( 'woocommerce_order_status_processing', 'change_role_on_purchase', 10, 2 );
add_action( 'woocommerce_order_status_completed', 'change_role_on_purchase', 10, 2 );
function change_role_on_purchase( $order_id, $order ) {
    $user = $order->get_user(); // Get the WP_User Object

    // Check for "customer" user roles only
    if( is_a( $user, 'WP_User' ) && in_array( 'customer', (array) $user->roles ) ) {
        // Remove WooCommerce "customer" role
        $user->remove_role( 'customer' ); 

        // Add new role
        $user->add_role( 'editor' );
    }
}