Support async render function in getDataFromTree / getMarkupFromTree

src/react/ssr/getDataFromTree.ts

@@ -18,7 +18,7 @@ export function getDataFromTree(
 export type GetMarkupFromTreeOptions = {
   tree: React.ReactNode;
   context?: { [key: string]: any };
-  renderFunction?: (tree: React.ReactElement<any>) => string;
+  renderFunction?: (tree: React.ReactElement<any>) => string | Promise<string>;
 };
 
 export function getMarkupFromTree({
@@ -31,14 +31,14 @@ export function getMarkupFromTree({
 }: GetMarkupFromTreeOptions): Promise<string> {
   const renderPromises = new RenderPromises();
 
-  function process(): Promise<string> | string {
+  async function process(): Promise<string> {
     // Always re-render from the rootElement, even though it might seem
     // better to render the children of the component responsible for the
     // promise, because it is not possible to reconstruct the full context
     // of the original rendering (including all unknown context provider
     // elements) for a subtree of the original component tree.
     const ApolloContext = getApolloContext();
-    const html = renderFunction(
+    const html = await renderFunction(
       React.createElement(
         ApolloContext.Provider,
         { value: { ...context, renderPromises } },