Adding and updating a custom shop order post status when upgrading WooCommerce 2.1 and below to 2.2 and up

custom-woocommerce-order-status.php

<?php
/*
Plugin Name: Custom Order Status for WooCommerce Shop Orders
Plugin URI:  http://scotcrop.com/2014/10/11/adding-and-updating-a-custom-shop-order-post-status-when-upgrading-woocommerce-2-1-and-below-to-2-2-and-up/
Description: Creates a new WooCommerce Order Status called In-Production and updates shop orders that were converted to a post status of 'publish' after upgrading from WooCommerce 2.1 and earlier to 2.2 and later.
Version:     1.0
Author:      Scott Cropper
Author URI:  http://scotcrop.com
License:     GPL2
License URI: https://www.gnu.org/licenses/gpl-2.0.html
*/

// Register a new post status to be used for WooCommmerce Orders
add_action( 'init', 'register_in_production_order_status' );

// Add a new order status to list of WC_Order statuses
add_filter( 'wc_order_statuses', 'add_in_production_order_status' );

// Run the update function when activated
register_activation_hook( __FILE__, 'update_published_orders' );

function register_in_production_order_status() {

    $args = array(
        'label'       => 'In-Production',
        'public'      => true,
        'label_count' => _n_noop( 'In-Production <span class="count">(%s)</span>', 'In-Production <span class="count">(%s)</span>' ),
    );

    register_post_status( 'wc-in-production', $args );

}


function add_in_production_order_status( $order_statuses ) {

    $updated_order_statuses = array();

    foreach ( $order_statuses as $key => $status ) {

        $updated_order_statuses[ $key ] = $status;

        // Check for and insert after 'Processing' order status
        if ( 'wc-processing' === $key ) {

            $updated_order_statuses['wc-in-production'] = 'In-Production';
        
        }
    
    }

    return $updated_order_statuses;

}


function update_published_orders() {

    // Adding post_status => 'publish' to these args would narrow the results but
    // you run into an issue with a WooCommerce filter trying to help and getting in the way
    // See
    // http://docs.woothemes.com/wc-apidocs/source-function-wc_shop_order_status_backwards_compatibility.html#669-715
    $args = array(
        'post_type' => 'shop_order',
        'posts_per_page' => -1,
    );

    $shop_orders = new WP_Query( $args );

    if ( $shop_orders->have_posts() ) { 

        while ( $shop_orders->have_posts() ) {

            $shop_orders->the_post();

            $post_id = get_the_id();

            if ( 'publish' == get_post_status( $post_id ) ) {

                $shop_order = array(
                  'ID' => $post_id,
                  'post_status' => 'wc-in-production',
                );

                wp_update_post( $shop_order );

            }

        }

    }

    wp_reset_postdata();

}

For some additional background on why this code is useful check out - http://develop.woothemes.com/woocommerce/2014/08/wc-2-2-order-statuses-plugin-compatibility/