If we have exceeded our allocated space for inlining objects defer any objects

eligible to be a lazy reference (other lazy references and elements).

This allows these to stream in on the client.

We ping these instead of retrying them, which places them after the currently
running task in the stream.

Author: sebmarkbage

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

@@ -160,6 +160,61 @@ describe('ReactFlightDOMEdge', () => {
     });
   }
 
+  function dripStream(input) {
+    const reader = input.getReader();
+    let nextDrop = 0;
+    let controller = null;
+    let streamDone = false;
+    const buffer = [];
+    function flush() {
+      if (controller === null || nextDrop === 0) {
+        return;
+      }
+      while (buffer.length > 0 && nextDrop > 0) {
+        const nextChunk = buffer[0];
+        if (nextChunk.byteLength <= nextDrop) {
+          nextDrop -= nextChunk.byteLength;
+          controller.enqueue(nextChunk);
+          buffer.shift();
+          if (streamDone && buffer.length === 0) {
+            controller.done();
+          }
+        } else {
+          controller.enqueue(nextChunk.subarray(0, nextDrop));
+          buffer[0] = nextChunk.subarray(nextDrop);
+          nextDrop = 0;
+        }
+      }
+    }
+    const output = new ReadableStream({
+      start(c) {
+        controller = c;
+        async function pump() {
+          for (;;) {
+            const {value, done} = await reader.read();
+            if (done) {
+              streamDone = true;
+              break;
+            }
+            buffer.push(value);
+            flush();
+          }
+        }
+        pump();
+      },
+      pull() {},
+      cancel(reason) {
+        reader.cancel(reason);
+      },
+    });
+    function drip(n) {
+      nextDrop += n;
+      flush();
+    }
+
+    return [output, drip];
+  }
+
   async function readResult(stream) {
     const reader = stream.getReader();
     let result = '';
@@ -576,6 +631,67 @@ describe('ReactFlightDOMEdge', () => {
     expect(serializedContent.length).toBeLessThan(150 + expectedDebugInfoSize);
   });
 
+  it('should break up large sync components by outlining into streamable elements', async () => {
+    const paragraphs = [];
+    for (let i = 0; i < 20; i++) {
+      const text =
+        'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris' +
+        'porttitor tortor ac lectus faucibus, eget eleifend elit hendrerit.' +
+        'Integer porttitor nisi in leo congue rutrum. Morbi sed ante posuere,' +
+        'aliquam lorem ac, imperdiet orci. Duis malesuada gravida pharetra. Cras' +
+        'facilisis arcu diam, id dictum lorem imperdiet a. Suspendisse aliquet' +
+        'tempus tortor et ultricies. Aliquam libero velit, posuere tempus ante' +
+        'sed, pellentesque tincidunt lorem. Nullam iaculis, eros a varius' +
+        'aliquet, tortor felis tempor metus, nec cursus felis eros aliquam nulla.' +
+        'Vivamus ut orci sed mauris congue lacinia. Cras eget blandit neque.' +
+        'Pellentesque a massa in turpis ullamcorper volutpat vel at massa. Sed' +
+        'ante est, auctor non diam non, vulputate ultrices metus. Maecenas dictum' +
+        'fermentum quam id aliquam. Donec porta risus vitae pretium posuere.' +
+        'Fusce facilisis eros in lacus tincidunt congue.' +
+        i; /* trick dedupe */
+      paragraphs.push(<p key={i}>{text}</p>);
+    }
+
+    const stream = await serverAct(() =>
+      ReactServerDOMServer.renderToReadableStream(paragraphs),
+    );
+
+    const [stream2, drip] = dripStream(stream);
+
+    // Allow some of the content through.
+    drip(5000);
+
+    const result = await ReactServerDOMClient.createFromReadableStream(
+      stream2,
+      {
+        serverConsumerManifest: {
+          moduleMap: null,
+          moduleLoading: null,
+        },
+      },
+    );
+
+    // We should have resolved enough to be able to get the array even though some
+    // of the items inside are still lazy.
+    expect(result.length).toBe(20);
+
+    // Unblock the rest
+    drip(Infinity);
+
+    // Use the SSR render to resolve any lazy elements
+    const ssrStream = await serverAct(() =>
+      ReactDOMServer.renderToReadableStream(result),
+    );
+    const html = await readResult(ssrStream);
+
+    const ssrStream2 = await serverAct(() =>
+      ReactDOMServer.renderToReadableStream(paragraphs),
+    );
+    const html2 = await readResult(ssrStream2);
+
+    expect(html).toBe(html2);
+  });
+
   it('should be able to serialize any kind of typed array', async () => {
     const buffer = new Uint8Array([
       123, 4, 10, 5, 100, 255, 244, 45, 56, 67, 43, 124, 67, 89, 100, 20,

packages/react-server/src/ReactFlightServer.js

@@ -1605,6 +1605,24 @@ let debugID: null | number = null;
 let serializedSize = 0;
 const MAX_ROW_SIZE = 3200;
 
+function deferTask(request: Request, task: Task): ReactJSONValue {
+  // Like outlineTask but instead the item is scheduled to be serialized
+  // after its parent in the stream.
+  const newTask = createTask(
+    request,
+    task.model, // the currently rendering element
+    task.keyPath, // unlike outlineModel this one carries along context
+    task.implicitSlot,
+    request.abortableTasks,
+    __DEV__ ? task.debugOwner : null,
+    __DEV__ ? task.debugStack : null,
+    __DEV__ ? task.debugTask : null,
+  );
+
+  pingTask(request, newTask);
+  return serializeLazyID(newTask.id);
+}
+
 function outlineTask(request: Request, task: Task): ReactJSONValue {
   const newTask = createTask(
     request,
@@ -2449,6 +2467,10 @@ function renderModelDestructive(
 
         const element: ReactElement = (value: any);
 
+        if (serializedSize > MAX_ROW_SIZE) {
+          return deferTask(request, task);
+        }
+
         if (__DEV__) {
           const debugInfo: ?ReactDebugInfo = (value: any)._debugInfo;
           if (debugInfo) {
@@ -2507,6 +2529,10 @@ function renderModelDestructive(
         return newChild;
       }
       case REACT_LAZY_TYPE: {
+        if (serializedSize > MAX_ROW_SIZE) {
+          return deferTask(request, task);
+        }
+
         // Reset the task's thenable state before continuing. If there was one, it was
         // from suspending the lazy before.
         task.thenableState = null;