[Fizz] Fix Suspense SSR content hidden for no-JS users (#35460)

packages/react-dom/src/__tests__/ReactDOMFizzServerNoScript-test.js

@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails react-core
+ * @jest-environment ./scripts/jest/ReactDOMServerIntegrationEnvironment
+ */
+
+'use strict';
+
+let React;
+let ReactDOMFizzServer;
+let Suspense;
+
+describe('ReactDOMFizzServerNoScript', () => {
+  beforeEach(() => {
+    jest.resetModules();
+    React = require('react');
+    Suspense = React.Suspense;
+    ReactDOMFizzServer = require('react-dom/server');
+  });
+
+  it('renders large content inline for no-JS support (size-based outlining disabled)', async () => {
+    // Generate content larger than progressiveChunkSize (100)
+    const largeContent = 'A'.repeat(2000);
+
+    function App() {
+      return (
+        <Suspense fallback="Loading...">
+          <div>{largeContent}</div>
+        </Suspense>
+      );
+    }
+
+    let streamedContent = '';
+    const writable = new (require('stream').Writable)({
+      write(chunk, encoding, callback) {
+        streamedContent += chunk.toString();
+        callback();
+      },
+    });
+
+    await new Promise(resolve => {
+      const {pipe} = ReactDOMFizzServer.renderToPipeableStream(<App />, {
+        progressiveChunkSize: 100,
+        onAllReady() {
+          pipe(writable);
+          resolve();
+        },
+      });
+    });
+
+    // Verify content is present in the initial stream (No-JS user sees it)
+    expect(streamedContent).toContain(largeContent);
+
+    // Verify fallback is NOT present (because it was inlined, so no pending state)
+    // Note: If it WAS outlined, we would see "Loading..."
+    expect(streamedContent).not.toContain('Loading...');
+  });
+});

packages/react-server/src/ReactFizzServer.js

@@ -5603,9 +5603,7 @@ function flushSegment(
     // blocked on something later in the stream anyway.
     !flushingPartialBoundaries &&
     isEligibleForOutlining(request, boundary) &&
-    (flushedByteSize + boundary.byteSize > request.progressiveChunkSize ||
-      hasSuspenseyContent(boundary.contentState) ||
-      boundary.defer)
+    (hasSuspenseyContent(boundary.contentState) || boundary.defer)
   ) {
     // Inlining this boundary would make the current sequence being written too large
     // and block the parent for too long. Instead, it will be emitted separately so that we