Apollo client, Discriminant loading in QueryResult type

[jsellam]

Hi everyone,

In react, when I use Apollo client for a query I got a QueryResult type with loading, data, and error.

in my code I have :

const result = useQuery(...)

if(result.loading){
 return <LoadingComponent />
}

if(result.error) {
 return <ErrorComponent />
}

if(result.data?.user){
 return <UserComponent user={result.data.user} />
}

I need to add a condition on if(result.data?.user) only for typescript. If loaded is set to true, and error to false, data should be present no ?
Actually there is no discriminant in the QueryResult definition. Do you think it could be a good new feature ?

[jsellam]

I have just seen that is the same feature request opened in 2019 #194

[phryneas]

There are various situations where loading might be false, no error is present and you still have no data - e.g. if you are currently skipping the query.
Unfortunately, it's not that simple and almost impossible to represent in types - it would be a big explosion of types, and you'd always have to check networkStatus, too, at least - a boolean alone will never be enough here.

That said, we will try to add some improvements in that direction in the future, but it will also get a lot better once you start using the suspenseful hooks like useSuspenseQuery instead of useQuery, as there are just no loading and error states to manage there.

[jsellam]

Thank you for you feeback @phryneas.
I understand the situation better now.

Actually I use assertIsDefined(result.data.user) before the final render. Suspence queries was in preview when I started my current project.