queryFn

[csotiMatyas]

Hey, somewhere between 5.62.1 and 5.83.0 a check was added in useBaseQuery:

(  if (process.env.NODE_ENV !== 'production') {
    if (!defaultedOptions.queryFn) {
      console.error(
        `[${defaultedOptions.queryHash}]: No queryFn was passed as an option, and no default queryFn was found. The queryFn parameter is only optional when using a default queryFn. More info here: https://tanstack.com/query/latest/docs/framework/react/guides/default-query-function`,
      )
    }
  })

So if you are no longer supposed to use useQuery w/o a queryFn, how do you subscribe to the cache? I assume everybody used useQuery with a key to just sub to a keys data before this change. I have really not enough time to fiddle with the internals, so is this an OKEY way to sub to a keys data:

export function useQueryObserver<
  TQueryFnData = unknown,
  TError = DefaultError,
  TData = TQueryFnData,
  TQueryKey extends QueryKey = QueryKey,
>(
  options: UndefinedInitialDataOptions<TQueryFnData, TError, TData, TQueryKey>
) {
  const queryClient = useQueryClient();
  const defaultedOptions = queryClient.defaultQueryOptions(options);
  const [observer] = useState(
    () => new QueryObserver(queryClient, defaultedOptions)
  );

  return useSyncExternalStore(
    useCallback(
      (onStoreChange) => {
        const unsubscribe = observer.subscribe(
          notifyManager.batchCalls(onStoreChange)
        );

        observer.updateResult();

        return unsubscribe;
      },
      [observer]
    ),
    () => observer.getCurrentResult(),
    () => observer.getCurrentResult()
  );
}

[TkDodo]

So if you are no longer supposed to use useQuery w/o a queryFn

this was never a supported pattern and at best an issue in the typings.

how do you subscribe to the cache?

by calling useQuery that has a queryFn ?

[csotiMatyas]

Thank you for the answer!
That's absolutely impractical to have a queryFn everywhere you want to access your data, and i can't image people are really doing it. That would mean you would need to save in state every querys arguments and later pass them in. Conceptually you have a place you fetch your data and you access that data everywhere in the app.

Or am i missing something crucial as this aproach seems straight up absurd. I modified my custom useQueryObserver to better reflect the one in the source and it works as expected so why is pushback?

Best regards

[TkDodo]

You need access to every query argument anyways because everything you use inside the queryFn must be part of the queryKey!