Function resume

packages/react-dom/src/server/ReactDOMFizzServerNode.js:370–442

(
  children: ReactNodeList,
  postponedState: PostponedState,
  options?: WebStreamsResumeOptions,
)

> & {signal: AbortSignal};

function resume(
  children: ReactNodeList,
  postponedState: PostponedState,
  options?: WebStreamsResumeOptions,
): Promise<ReactDOMServerReadableStream> {
  return new Promise((resolve, reject) => {
    let onFatalError;
    let onAllReady;
    const allReady = new Promise<void>((res, rej) => {
      onAllReady = res;
      onFatalError = rej;
    });

    function onShellReady() {
      let writable: Writable;
      const stream: ReactDOMServerReadableStream = (new ReadableStream(
        {
          type: 'bytes',
          start: (controller): ?Promise<void> => {
            writable =
              createFakeWritableFromReadableStreamController(controller);
          },
          pull: (controller): ?Promise<void> => {
            startFlowing(request, writable);
          },
          cancel: (reason): ?Promise<void> => {
            stopFlowing(request);
            abort(request, reason);
          },
        },
        // $FlowFixMe[prop-missing] size() methods are not allowed on byte streams.
        {highWaterMark: 0},
      ): any);
      // TODO: Move to sub-classing ReadableStream.
      stream.allReady = allReady;
      resolve(stream);
    }
    function onShellError(error: mixed) {
      // If the shell errors the caller of `renderToReadableStream` won't have access to `allReady`.
      // However, `allReady` will be rejected by `onFatalError` as well.
      // So we need to catch the duplicate, uncatchable fatal error in `allReady` to prevent a `UnhandledPromiseRejection`.
      allReady.catch(() => {});
      reject(error);
    }
    const request = resumeRequest(
      children,
      postponedState,
      resumeRenderState(
        postponedState.resumableState,
        options ? options.nonce : undefined,
      ),
      options ? options.onError : undefined,
      onAllReady,
      onShellReady,
      onShellError,
      onFatalError,
      options ? options.onPostpone : undefined,
    );