Variant data missing on Purchase event for Woocommerce variable subscriptions

[Jasperste]

Hello there,

We are using GA4 for Ecommerce tracking for our Woocommerce site with Woocommerce subscriptions using GTM4WP. We seem to have configured everything properly, when testing the view with Tag Manager we for example see the following for addToCart:

  event: "add_to_cart",
  ...
  productType: "variable-subscription",
  productIsVariable: 0,
  ecomm_prodid: "508",
  ecomm_pagetype: "product",
  ecomm_totalvalue: 64.99,
  ecommerce: {
    currencyCode: "EUR",
    detail: {
      products: [
        {
          id: 508,
          name: "Running on track",
          sku: "running-01",
          category: "training",
          price: 64.99,
          stocklevel: "",
          brand: "trainingcoach",
          variant: "bronze"
        }
      ]
    },
    currency: "EUR",
    value: 64.99,
    items: [
      {
        item_id: 508,
        item_name: "Running on track",
        item_brand: "trainingcoach",
        price: 64.99,
        item_category: "training",
        google_business_vertical: "retail",
        id: "508",
        item_variant: "bronze",
        quantity: "1"
      }
    ],
    add: {
      products: [
        {
          name: "Name",
          id: 508,
          price: 64.99,
          category: "training",
          stocklevel: "",
          brand: "trainingcoach",
          variant: "bronze",
          quantity: "1"
        }
      ]
    }
  },

This is for a variable subscription with variants. As you can see it registers the variant correctly, so we are able to differentiate that this is a variant of product X. However when we do the actual purchase the data is different (I used a 100% off coupon):

  event: "purchase",
  ...
  ecommerce: {
    currencyCode: "EUR",
    purchase: {
      actionField: {
        id: "x_y_z",
        affiliation: "",
        revenue: 0,
        tax: 0,
        shipping: 0,
        coupon: "mydiscount1"
      },
      products: [
        {
          id: 508,
          name: "Running on track",
          sku: "running-01",
          category: "",
          price: 0,
          stocklevel: null,
          brand: "",
          quantity: 1
        }
      ]
    },
    currency: "EUR",
    items: [
      {
        item_id: 508,
        item_name: "Running on track",
        item_brand: "",
        price: "",
        item_category: "",
        quantity: 1,
        google_business_vertical: "retail",
        id: "508"
      }
    ],
    transaction_id: "x_y_z",
    affiliation: "",
    value: 0,
    tax: 0,
    shipping: 0,
    coupon: "mydiscount1"
  },
  ecomm_prodid: [508],
  ecomm_pagetype: "purchase",

It now misses out on the variant data (variant: "bronze". Is this expected, a misconfiguration on our side or is this a bug? It seems like the latter where the purchase doesn't get registered correctly and holding the variant data. Also some other data seems to be missing like category being an empty string.

Happy to approve a PR or create a PR with the right pointers, if this can be solved within this repo.

Expected
The Purchase event to hold data about the variant, similar to the addToCart event.

Actual
The Purchase event doesn't mention anything about the variant, in this case it's being the bronze variant.