johncraigcole/hydrogen-v2-available-shipping-rates-cart-issue

Hydrogen Bug Replication for Storefront API carts with both errors and cart in a single response

When a buyer has been associated to a Storefront API cart a specific buyerIdentity fragment can cause a Storefront API cart query or mutation response to have both a valid cart and errors attributes. This happens when asking for the customer.lastIncompleteCheckout.availableShippingRates of the buyerIdentity on the cart query or mutation response. Here's an example of a BuyerIdentity graphql fragment asking for the info that causes a Shipping Address Can't Be Blank error unless a shipping address has been previously provided at checkout for the cart.

fragment buyer on BuyerIdentity {
  customer {
    lastIncompletCheckout {
      availableShippingRates {
        shippingRates {
          handle
        }
      }
    }
  }
}

At the moment, Hydrogen 2023.10.0 (and earlier) throw an error for any presence of a Storefront API mutaion or query response that contains errors in the response. With the cart query happening at the root, this error causes the app to crash.

Summary of Replication Project

This repo uses Hydrogen 2023.10.0 to provide a reproducilbe flow based on the demo starter template with tweaks to make reproducing the issue easier.

1. Added a custom cart handler in server.js that facilitates handling both line item add and buyer identity update of a Storefront API request in a single post.
2. Added a new cart action to cart.jsx route to invoke the custom cart handler function.
3. Added two new cart buttons to the PDP route. First, Add To Cart with Buyer Identity adds an item and buyer identity to the cart without using a query that will cause a cart error. Second Add To Cart with Buyer Identity Without Crash Protection that will switch the root cart query to one that will cause an error. These two buttons act like toggles setting a cookie crashprotection that signals to server.js to use a cart query that causes an error. crashprotection=off will cause the error, while the crashprotection cookie not being present, or any other value than off will force the use of a safe cart query.