How to update/change an order in google analytics - google-analytics

Question

So I've been fiddling with this for a while now and I can't wrap my head around how analytics does it's calculations on purchases when updating an order with new/changed products.
I'm utilizing the datalayer(dl) and push my purchase event to the dl, which GTM listens to via a trigger event, all standard so far.
{
"event": "purchase",
"currencyCode": "SEK",
"ecommerce": {
"purchase": {
"actionField": {
"id": "123",
"tax": 30.0,
"action": "purchase"
},
"products": [
{
"name": "name",
"id": "123",
"price": "5.0",
"brand": "brand",
"category": "category",
"quantity": 2
}
]
}
}
}
But then our customers has the ability to change their orders. So with a bit of research On here I was able to defer that you can add products with a negative quantity on the existing order to remove products after a changed order.
So this resulted in, something not optimal but it works for the orders products atleast. In this case I want one more item of the same. So I do this:
{
"event": "purchase",
"currencyCode": "SEK",
"ecommerce": {
"purchase": {
"actionField": {
"id": "123",
"tax": newTax -= oldTax,
"action": "purchase"
},
"products": [
{
"name": "name",
"id": "123",
"price": "5.0",
"brand": "brand",
"category": "category",
"quantity": 3
},
{
"name": "name",
"id": "123",
"price": "5.0",
"brand": "brand",
"category": "category",
"quantity": -2
}
]
}
}
}
And it works for everything except the total of the purchase. Since that's calculated based on the products in the order why doesn't that update automatically when I update the order? Do I need to send in the oldTotal -= newTotal as well or is there a delay in the recalculations in analytics?

Answer 1

Instead of letting it calculate the total revenue on its own, have you tried adding the total revenue, total tax and total shipping on your own. These fields are present in the actionField as follows:-
"actionField": {
"id": "123",
"action": "purchase"
'revenue': 'newRev - oldRev', // difference of new revenue and old revenue
'tax':'newTax - oldTax', // difference of new tax and old tax
'shipping': 'newShipping - oldShipping' // difference of new shipping and old shipping
},
Of course do add the products as well.
In the canned GA reports, it will automatically add the old revenue and the new revenue amounts and use that as the revenue total.