I would like to use App-data metafields and tried it. But “Unexpected error” occurred when I executed metafieldsSet mutation according to this document.
The steps are:
Create a Shopify app and create an access token including all access scopes.
It does look like you’re following the docs correctly, so I’ve reached out to our internal devs to see if there’s an issue on our side. When you get this error is there any response error codes returned too?
It seems that this is a bug on our side, related to how app reserved namespaces are used with app data metafields. While we work on a fix for this, a workaround would be to specify a non-app reserverved namespace. (for example: “custom”, and not “$app:foo” or “app–{YOURAPPID}–foo”)
I have the same issue (getting “Unexpected system error. Try again later.”) using a reserved namespace and while using a non-app reserved namespace work, it’s clearly an issue regarding on critical parts like Checkout Functions (as stated here: https://shopify.dev/docs/apps/functions/input-output/variables-queries)