Add a unit test for deduped owner objects

Repro from vercel/next.js#69545

Author: unstubbable

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

@@ -630,6 +630,83 @@ describe('ReactFlightDOMBrowser', () => {
     expect(container.innerHTML).toBe('<div></div>');
   });
 
+  it('should handle references to deduped owner objects', async () => {
+    // This is replicating React components as generated by @svgr/webpack:
+    let path1: React.ReactNode;
+    let path2: React.ReactNode;
+
+    function Svg1() {
+      return ReactServer.createElement(
+        'svg',
+        {id: '1'},
+        path1 || (path1 = ReactServer.createElement('path', {})),
+      );
+    }
+
+    function Svg2() {
+      return ReactServer.createElement(
+        'svg',
+        {id: '2'},
+        path2 || (path2 = ReactServer.createElement('path', {})),
+      );
+    }
+
+    function Server() {
+      return ReactServer.createElement(
+        ReactServer.Fragment,
+        {},
+        ReactServer.createElement(Svg1),
+        ReactServer.createElement(Svg2),
+      );
+    }
+
+    let stream = await serverAct(() =>
+      ReactServerDOMServer.renderToReadableStream(<Server />, webpackMap),
+    );
+
+    function ClientRoot({response}) {
+      return use(response);
+    }
+
+    let response = ReactServerDOMClient.createFromReadableStream(stream);
+    const container = document.createElement('div');
+    const root = ReactDOMClient.createRoot(container);
+
+    await act(() => {
+      root.render(<ClientRoot response={response} />);
+    });
+
+    const expectedHtml =
+      '<svg id="1"><path></path></svg><svg id="2"><path></path></svg>';
+
+    expect(container.innerHTML).toBe(expectedHtml);
+
+    // Render a second time:
+
+    // Assigning the path elements to variables in module scope (here simulated
+    // with the test's function scope), and rendering a second time, prevents
+    // the owner of the path elements (i.e. Svg1/Svg2) to be deduped. The owner
+    // of the path in Svg1 is fully inlined. The owner of the owner of the path
+    // in Svg2 is Server, which is deduped and replaced with a reference to the
+    // owner of the owner of the path in Svg1. This nested owner is actually
+    // Server from the previous render pass, which is kinda broken and libaries
+    // probably shouldn't generate code like this. This reference can only be
+    // resolved properly if owners are specifically handled when resolving
+    // outlined models.
+
+    stream = await serverAct(() =>
+      ReactServerDOMServer.renderToReadableStream(<Server />, webpackMap),
+    );
+
+    response = ReactServerDOMClient.createFromReadableStream(stream);
+
+    await act(() => {
+      root.render(<ClientRoot response={response} />);
+    });
+
+    expect(container.innerHTML).toBe(expectedHtml);
+  });
+
   it('should progressively reveal server components', async () => {
     let reportedErrors = [];