Woocommerce REST API v2: Issue with adding custom data to orders - woocommerce

Question

I have a site running an old version of Woo v2.5.5 using legacy v3 for the API. I was able to use the action woocommerce_api_order_response to add data to the orders.
Something like:
add_action( 'woocommerce_api_order_response', 'add_testing_api_function', 10, 1 );
function add_testing_api_function( $order_data ) {
$order_data['foo'] = "testing";
return $order_data;
}
This works fine over the older API link:
https://example.com/wc-api/v3/orders?consumer_key=KEY&consumer_secret=SECRET
However, I need to update to Woo v3.3+ and the REST API is server up as:
https://example.com/wp-json/wc/v2/orders?consumer_key=KEY&consumer_secret=SECRET
My custom data no longer appears, and the hook does not appear to work. Is there another I can use?

Answer 1

WC API is indeed a great tool. Adding your own custom data to WC API shop order's response in WooCommerce 3.x can still be achieved as easily as it used to be with the legacy version of the API.
WooCommerce has these prepare filters for most of their API responses (see). Note that the format of them is woocommerce_rest_prepare_{$post_type}, where $post_type is a post type or taxonomy name like shop_orders or product_cat. In WooCommerce 2.7+ some of these filters also have a _object suffix.
As long as our intent is to add custom data to orders, the right filter to use will be woocommerce_rest_prepare_shop_order_object, where shop_order is our {$post_type} followed the _object suffix (as described above).
The following function conditionally gets user meta and returns the user's social profile's avatar url if available.
/**
* Add custom data to WC API shop order response
* Overriding "$object" here with $order so it's easier to access its properties
*/
function my_wc_rest_prepare_order( $response, $order, $request ) {
if( empty( $response->data ) )
return $response;
$order_id = $order->get_id();
// Get an instance of the WC_Order object
$order = wc_get_order($order_id);
// Get the user ID from WC_Order methods
$user_id = $order->get_customer_id(); // $order->get_user_id(); // or $order->get_customer_id();
// check for WooCommerce Social Login User Avatar
if( class_exists( 'WC_Social_Login' ) ) {
$fb_avatar = get_user_meta( $user_id, '_wc_social_login_facebook_profile_image', true );
$gplus_avatar = get_user_meta( $user_id, '_wc_social_login_google_profile_image', true );
}
$social_data = array();
$avatar_url = array();
$customer_picture = array(
'default' => get_avatar_url( $user_id ),
'facebook' => ( $fb_avatar ) ? esc_url( $fb_avatar ) : '',
'google' => ( $gplus_avatar ) ? esc_url( $gplus_avatar ) : ''
);
$response->data['social_data']['avatar_url'] = $customer_picture;
return $response;
}
add_filter( 'woocommerce_rest_prepare_shop_order_object', 'my_wc_rest_prepare_order', 10, 3 );
Result:
[{
"social_data": {
"avatar_url": {
"default": "https://secure.gravatar.com/avatar/6e27402273b47316097247a2057492f8?s=96&d=mm&r=g",
"facebook": "https://graph.facebook.com/2028542057604385/picture?width=150&height=150",
"google": ""
}
},
}]