Function streamedQuery

packages/query-core/src/streamedQuery.ts:51–120

({
  streamFn,
  refetchMode = 'reset',
  reducer = (items, chunk) =>
    addToEnd(items as Array<TQueryFnData>, chunk) as TData,
  initialValue = [] as TData,
}: StreamedQueryParams<TQueryFnData, TData, TQueryKey>)

 * @param initialValue - Initial value to be used while the first chunk is being fetched, and returned if the stream yields no values.
 */
export function streamedQuery<
  TQueryFnData = unknown,
  TData = Array<TQueryFnData>,
  TQueryKey extends QueryKey = QueryKey,
>({
  streamFn,
  refetchMode = 'reset',
  reducer = (items, chunk) =>
    addToEnd(items as Array<TQueryFnData>, chunk) as TData,
  initialValue = [] as TData,
}: StreamedQueryParams<TQueryFnData, TData, TQueryKey>): QueryFunction<
  TData,
  TQueryKey
> {
  return async (context) => {
    const query = context.client
      .getQueryCache()
      .find({ queryKey: context.queryKey, exact: true })
    const isRefetch = !!query && query.isFetched()
    if (isRefetch && refetchMode === 'reset') {
      query.setState({
        ...query.resetState,
        fetchStatus: 'fetching',
      })
    }

    let result = initialValue

    let cancelled: boolean = false as boolean
    const streamFnContext = addConsumeAwareSignal<
      OmitKeyof<typeof context, 'signal'>
    >(
      {
        client: context.client,
        meta: context.meta,
        queryKey: context.queryKey,
        pageParam: context.pageParam,
        direction: context.direction,
      },
      () => context.signal,
      () => (cancelled = true),
    )

    const stream = await streamFn(streamFnContext)

    const isReplaceRefetch = isRefetch && refetchMode === 'replace'

    for await (const chunk of stream) {
      if (cancelled) {
        break
      }

      if (isReplaceRefetch) {
        // don't append to the cache directly when replace-refetching
        result = reducer(result, chunk)
      } else {
        context.client.setQueryData<TData>(context.queryKey, (prev) =>
          reducer(prev === undefined ? initialValue : prev, chunk),