I am attempting to work on some integration with Shopify and Shippo, part of the process is sending an email to our warehouse including the order line items with the Shipping Label attached as a PDF.
When we create the label in Shippo, the fulfillment information is updated in Shopify correctly, but I was wondering if there was any way to link the two back up reliably from an API perspective since the Shippo API appears to not include any invoice information. I see a link to an internal order object, but the API docs don't seem to stipulate any further information and the Shopify Fulfillment record does not appear to include any Shippo object id.
The only thing I see if the Shippo Order Metadata field which includes the order number, so I suppose I could parse this and make the request to Shopify's API but I would prefer a more concrete link if one is available.
We (I'm working on Shippo's product team) currently don't officially support Shopify Fulfillments with Shippo API label purchases.
That said, we have an Orders API endpoint in beta. The Orders endpoint allows you to retrieve all Orders of a Shippo account, including those imported automatically from Shopify. Each order, like all other Shippo resources, has an object_id field.
When you create a label through the Shippo API's Transaction endpoint, you can link the Order to the Transaction by sending the additional flag order, setting it to the object_id of the corresponding Order (e.g.: { ... "order": "<order-object-id>" ... }). This will trigger the corresponding Fulfillment of the order on its shopping cart platform, in your case Shopify.
Feel free to reach out to product@goshippo.com if you have more questions about this endpoint. Please keep in mind that it is still in closed beta and the endpoint might change in the future.