Function prerender

packages/react-dom/src/server/ReactDOMFizzStaticNode.js:192–285

(
  children: ReactNodeList,
  options?: Omit<Options, 'onHeaders'> & {
    onHeaders?: (headers: Headers) => void,
  },
)

}

function prerender(
  children: ReactNodeList,
  options?: Omit<Options, 'onHeaders'> & {
    onHeaders?: (headers: Headers) => void,
  },
): Promise<{
  postponed: null | PostponedState,
  prelude: ReadableStream,
}> {
  return new Promise((resolve, reject) => {
    const onFatalError = reject;

    function onAllReady() {
      let writable: Writable;
      const stream = 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},
      );

      const result =
        enablePostpone || enableHalt
          ? {
              postponed: getPostponedState(request),
              prelude: stream,
            }
          : ({
              prelude: stream,
            }: any);
      resolve(result);
    }

    const onHeaders = options ? options.onHeaders : undefined;
    let onHeadersImpl;
    if (onHeaders) {
      onHeadersImpl = (headersDescriptor: HeadersDescriptor) => {
        onHeaders(new Headers(headersDescriptor));
      };
    }
    const resources = createResumableState(
      options ? options.identifierPrefix : undefined,
      options ? options.unstable_externalRuntimeSrc : undefined,
      options ? options.bootstrapScriptContent : undefined,
      options ? options.bootstrapScripts : undefined,
      options ? options.bootstrapModules : undefined,