Add iterator support as Replies

Author: sebmarkbage

packages/react-client/src/ReactFlightReplyClient.js

@@ -15,6 +15,7 @@ import {
   REACT_ELEMENT_TYPE,
   REACT_LAZY_TYPE,
   REACT_PROVIDER_TYPE,
+  getIteratorFn,
 } from 'shared/ReactSymbols';
 
 import {
@@ -159,6 +160,12 @@ export function processReply(
         );
         return serializePromiseID(promiseId);
       }
+      if (!isArray(value)) {
+        const iteratorFn = getIteratorFn(value);
+        if (iteratorFn) {
+          return Array.from((value: any));
+        }
+      }
 
       if (__DEV__) {
         if (value !== null && !isArray(value)) {

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMReply-test.js

@@ -17,14 +17,12 @@ global.TextDecoder = require('util').TextDecoder;
 
 // let serverExports;
 let webpackServerMap;
-let act;
 let ReactServerDOMServer;
 let ReactServerDOMClient;
 
 describe('ReactFlightDOMReply', () => {
   beforeEach(() => {
     jest.resetModules();
-    act = require('internal-test-utils').act;
     const WebpackMock = require('./utils/WebpackMock');
     // serverExports = WebpackMock.serverExports;
     webpackServerMap = WebpackMock.webpackServerMap;
@@ -57,4 +55,23 @@ describe('ReactFlightDOMReply', () => {
     expect('3' in object.array).toBe(false);
     expect('prop' in object).toBe(false);
   });
+
+  it('can pass an iterable as a reply', async () => {
+    const body = await ReactServerDOMClient.encodeReply({
+      [Symbol.iterator]: function* () {
+        yield 'A';
+        yield 'B';
+        yield 'C';
+      },
+    });
+    const iterable = await ReactServerDOMServer.decodeReply(
+      body,
+      webpackServerMap,
+    );
+    const items = [];
+    for (const item of iterable) {
+      items.push(item);
+    }
+    expect(items).toEqual(['A', 'B', 'C']);
+  });
 });