Function ensureQueryFn

packages/query-core/src/utils.ts:534–565

(
  options: {
    queryFn?: QueryFunction<TQueryFnData, TQueryKey> | SkipToken
    queryHash?: string
  },
  fetchOptions?: FetchOptions<TQueryFnData>,
)

export type SkipToken = typeof skipToken

export function ensureQueryFn<
  TQueryFnData = unknown,
  TQueryKey extends QueryKey = QueryKey,
>(
  options: {
    queryFn?: QueryFunction<TQueryFnData, TQueryKey> | SkipToken
    queryHash?: string
  },
  fetchOptions?: FetchOptions<TQueryFnData>,
): QueryFunction<TQueryFnData, TQueryKey> {
  if (process.env.NODE_ENV !== 'production') {
    if (options.queryFn === skipToken) {
      console.error(
        `Attempted to invoke queryFn when set to skipToken. This is likely a configuration error. Query hash: '${options.queryHash}'`,
      )
    }
  }

  // if we attempt to retry a fetch that was triggered from an initialPromise
  // when we don't have a queryFn yet, we can't retry, so we just return the already rejected initialPromise
  // if an observer has already mounted, we will be able to retry with that queryFn
  if (!options.queryFn && fetchOptions?.initialPromise) {
    return () => fetchOptions.initialPromise!
  }

  if (!options.queryFn || options.queryFn === skipToken) {
    return () =>
      Promise.reject(new Error(`Missing queryFn: '${options.queryHash}'`))
  }

  return options.queryFn
}

/**
 * Resolves a `throwOnError` option to a boolean.