Recommended way to type useQuery data if we know it cannot be undefined?

[taylorkline]

I have a query that is ran in an AppLoader component to fetch some app-wide account data. Unless that data is successfully retrieved, none of its children could possibly be rendered.

Given that, how can I intelligently type data from useGetAccountQuery / useGetAccountQueryState to indicate that it cannot possibly be undefined?

Right now I have:

  // @ts-ignore: data will be AccountResponse here
  const { data }: { data: AccountResponse } = useGetAccountQuery();

But I know that this is completely silly and unsafe since, for example, changing the ResultType of the getAccount endpoint would not raise any warnings.

How can I just type data as ResultType instead of ResultType | undefined?

This is probably trivial to anyone with more familiarity with TypeScipt than I, so thank you in advance for your help.

[phryneas]

Hmm. Something like

function assertHasData<T>(x: {data?: T}): asserts x is {data: T} {}


const result = useGetAccountQuery();
assertHasData(result)

// result.data is defined here

or

function assertIsDefined<T>(x: T|undefined): asserts x is T {}


const { data } = useGetAccountQuery();
assertIsDefined(data)

// data is defined here

[taylorkline]

Thanks, super helpful!