implement basic streaming for renderIntoContainer

Author: gnoff

packages/react-dom-bindings/src/client/ReactDOMHostConfig.js

@@ -15,7 +15,7 @@ import type {
   IntersectionObserverOptions,
   ObserveVisibleRectsCallback,
 } from 'react-reconciler/src/ReactTestSelectors';
-import type {ReactScopeInstance} from 'shared/ReactTypes';
+import type {ReactScopeInstance, Thenable} from 'shared/ReactTypes';
 import type {AncestorInfoDev} from './validateDOMNesting';
 
 import {
@@ -1409,6 +1409,24 @@ export function errorHydratingContainer(parentContainer: Container): void {
   }
 }
 
+export function getHydrationReadySignal(
+  container: Container,
+): null | Thenable<mixed> {
+  const signal = (container: any)._r;
+  if (
+    signal !== null &&
+    typeof signal === 'object' &&
+    typeof signal.then === 'function'
+  ) {
+    return signal;
+  }
+  return null;
+}
+
+export function clearHydrationReadySignal(container: Container) {
+  (container: any)._r = null;
+}
+
 // -------------------
 //     Test Selectors
 // -------------------

packages/react-dom-bindings/src/server/ReactDOMServerExternalRuntime.js

@@ -11,6 +11,7 @@ import {
   clientRenderBoundary,
   completeBoundaryWithStyles,
   completeBoundary,
+  completeContainer,
   completeSegment,
 } from './fizz-instruction-set/ReactDOMFizzInstructionSet';
 
@@ -81,6 +82,7 @@ function handleNode(node_ /*: Node */) {
   // $FlowFixMe[incompatible-cast]
   const node = (node_ /*: HTMLElement*/);
   const dataset = node.dataset;
+  let register = '';
   if (dataset['rxi'] != null) {
     clientRenderBoundary(
       dataset['bid'],
@@ -89,16 +91,21 @@ function handleNode(node_ /*: Node */) {
       dataset['stck'],
     );
     node.remove();
-  } else if (dataset['rri'] != null) {
+  } else if ((register = dataset['rri']) != null) {
     // Convert styles here, since its type is Array<Array<string>>
     completeBoundaryWithStyles(
+      register === 'c',
       dataset['bid'],
       dataset['sid'],
       JSON.parse(dataset['sty']),
     );
     node.remove();
-  } else if (dataset['rci'] != null) {
-    completeBoundary(dataset['bid'], dataset['sid']);
+  } else if ((register = dataset['rci']) != null) {
+    if (register === 'c') {
+      completeContainer(dataset['bid'], dataset['sid']);
+    } else {
+      completeBoundary(dataset['bid'], dataset['sid']);
+    }
     node.remove();
   } else if (dataset['rsi'] != null) {
     completeSegment(dataset['sid'], dataset['pid']);