Support Iterables in Flight

Author: sebmarkbage

packages/react-client/src/__tests__/ReactFlight-test.js

@@ -166,6 +166,34 @@ describe('ReactFlight', () => {
     expect(ReactNoop).toMatchRenderedOutput(<span>Hello, Seb Smith</span>);
   });
 
+  it('can render an iterable as an array', async () => {
+    function ItemListClient(props) {
+      return <span>{props.items}</span>;
+    }
+    const ItemList = clientReference(ItemListClient);
+
+    function Items() {
+      const iterable = {
+        [Symbol.iterator]: function* () {
+          yield 'A';
+          yield 'B';
+          yield 'C';
+        },
+      };
+      return <ItemList items={iterable} />;
+    }
+
+    const model = <Items />;
+
+    const transport = ReactNoopFlightServer.render(model);
+
+    await act(async () => {
+      ReactNoop.render(await ReactNoopFlightClient.read(transport));
+    });
+
+    expect(ReactNoop).toMatchRenderedOutput(<span>ABC</span>);
+  });
+
   it('can render a lazy component as a shared component on the server', async () => {
     function SharedComponent({text}) {
       return (

packages/react-server/src/ReactFlightServer.js

@@ -73,6 +73,7 @@ import {
 } from './ReactFlightNewContext';
 
 import {
+  getIteratorFn,
   REACT_ELEMENT_TYPE,
   REACT_FORWARD_REF_TYPE,
   REACT_FRAGMENT_TYPE,
@@ -1053,6 +1054,12 @@ export function resolveModelToJSON(
       }
       return (undefined: any);
     }
+    if (!isArray(value)) {
+      const iteratorFn = getIteratorFn(value);
+      if (iteratorFn) {
+        return Array.from((value: any));
+      }
+    }
 
     if (__DEV__) {
       if (value !== null && !isArray(value)) {