Fizz implementation

This is semantically the same as just throwing an error. It just triggers client rendering. The difference is in how it gets logged. On the server we log to onPostpone instead of onError. On the client this doesn't trigger a recoverable error. It's just silent since it was intentional.
facebook · Aug 17, 2023 · dbcc12f · dbcc12f
1 parent eec516e
commit dbcc12f
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diff --git a/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js b/packages/react-dom/src/__tests__/ReactDOMFizzServer-test.js
@@ -6040,4 +6040,95 @@ describe('ReactDOMFizzServer', () => {
       console.error = originalConsoleError;
     }
   });
+
+  // @gate enablePostpone
+  it('client renders postponed boundaries without erroring', async () => {
+    function Postponed({isClient}) {
+      if (!isClient) {
+        React.unstable_postpone('testing postpone');
+      }
+      return 'client only';
+    }
+
+    function App({isClient}) {
+      return (
+        <div>
+          <Suspense fallback={'loading...'}>
+            <Postponed isClient={isClient} />
+          </Suspense>
+        </div>
+      );
+    }
+
+    const errors = [];
+
+    await act(() => {
+      const {pipe} = renderToPipeableStream(<App isClient={false} />, {
+        onError(error) {
+          errors.push(error.message);
+        },
+      });
+      pipe(writable);
+    });
+
+    expect(getVisibleChildren(container)).toEqual(<div>loading...</div>);
+
+    ReactDOMClient.hydrateRoot(container, <App isClient={true} />, {
+      onRecoverableError(error) {
+        errors.push(error.message);
+      },
+    });
+    await waitForAll([]);
+    // Postponing should not be logged as a recoverable error since it's intentional.
+    expect(errors).toEqual([]);
+    expect(getVisibleChildren(container)).toEqual(<div>client only</div>);
+  });
+
+  // @gate enablePostpone
+  it('errors if trying to postpone outside a Suspense boundary', async () => {
+    function Postponed() {
+      React.unstable_postpone('testing postpone');
+      return 'client only';
+    }
+
+    function App() {
+      return (
+        <div>
+          <Postponed />
+        </div>
+      );
+    }
+
+    const errors = [];
+    const fatalErrors = [];
+    const postponed = [];
+    let written = false;
+
+    const testWritable = new Stream.Writable();
+    testWritable._write = (chunk, encoding, next) => {
+      written = true;
+    };
+
+    await act(() => {
+      const {pipe} = renderToPipeableStream(<App />, {
+        onPostpone(reason) {
+          postponed.push(reason);
+        },
+        onError(error) {
+          errors.push(error.message);
+        },
+        onShellError(error) {
+          fatalErrors.push(error.message);
+        },
+      });
+      pipe(testWritable);
+    });
+
+    expect(written).toBe(false);
+    // Postponing is not logged as an error but as a postponed reason.
+    expect(errors).toEqual([]);
+    expect(postponed).toEqual(['testing postpone']);
+    // However, it does error the shell.
+    expect(fatalErrors).toEqual(['testing postpone']);
+  });
 });
diff --git a/packages/react-dom/src/__tests__/ReactDOMFizzServerBrowser-test.js b/packages/react-dom/src/__tests__/ReactDOMFizzServerBrowser-test.js
@@ -503,4 +503,43 @@ describe('ReactDOMFizzServerBrowser', () => {
       `"<link rel="preload" href="init.js" as="script" fetchPriority="low" nonce="R4nd0m"/><link rel="modulepreload" href="init.mjs" fetchPriority="low" nonce="R4nd0m"/><div>hello world</div><script nonce="${nonce}">INIT();</script><script src="init.js" nonce="${nonce}" async=""></script><script type="module" src="init.mjs" nonce="${nonce}" async=""></script>"`,
     );
   });
+
+  // @gate enablePostpone
+  it('errors if trying to postpone outside a Suspense boundary', async () => {
+    function Postponed() {
+      React.unstable_postpone('testing postpone');
+      return 'client only';
+    }
+
+    function App() {
+      return (
+        <div>
+          <Postponed />
+        </div>
+      );
+    }
+
+    const errors = [];
+    const postponed = [];
+
+    let caughtError = null;
+    try {
+      await ReactDOMFizzServer.renderToReadableStream(<App />, {
+        onError(error) {
+          errors.push(error.message);
+        },
+        onPostpone(reason) {
+          postponed.push(reason);
+        },
+      });
+    } catch (error) {
+      caughtError = error;
+    }
+
+    // Postponing is not logged as an error but as a postponed reason.
+    expect(errors).toEqual([]);
+    expect(postponed).toEqual(['testing postpone']);
+    // However, it does error the shell.
+    expect(caughtError.message).toEqual('testing postpone');
+  });
 });
diff --git a/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js b/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
@@ -35,6 +35,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -100,6 +101,7 @@ function renderToReadableStream(
       onShellReady,
       onShellError,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMFizzServerBun.js b/packages/react-dom/src/server/ReactDOMFizzServerBun.js
@@ -35,6 +35,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -101,6 +102,7 @@ function renderToReadableStream(
       onShellReady,
       onShellError,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMFizzServerEdge.js b/packages/react-dom/src/server/ReactDOMFizzServerEdge.js
@@ -35,6 +35,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -100,6 +101,7 @@ function renderToReadableStream(
       onShellReady,
       onShellError,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMFizzServerNode.js b/packages/react-dom/src/server/ReactDOMFizzServerNode.js
@@ -49,6 +49,7 @@ type Options = {
   onShellError?: (error: mixed) => void,
   onAllReady?: () => void,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -80,6 +81,7 @@ function createRequestImpl(children: ReactNodeList, options: void | Options) {
     options ? options.onShellReady : undefined,
     options ? options.onShellError : undefined,
     undefined,
+    options ? options.onPostpone : undefined,
   );
 }
 

diff --git a/packages/react-dom/src/server/ReactDOMFizzStaticBrowser.js b/packages/react-dom/src/server/ReactDOMFizzStaticBrowser.js
@@ -34,6 +34,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -85,6 +86,7 @@ function prerender(
       undefined,
       undefined,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMFizzStaticEdge.js b/packages/react-dom/src/server/ReactDOMFizzStaticEdge.js
@@ -34,6 +34,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -85,6 +86,7 @@ function prerender(
       undefined,
       undefined,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMFizzStaticNode.js b/packages/react-dom/src/server/ReactDOMFizzStaticNode.js
@@ -36,6 +36,7 @@ type Options = {
   progressiveChunkSize?: number,
   signal?: AbortSignal,
   onError?: (error: mixed) => ?string,
+  onPostpone?: (reason: string) => void,
   unstable_externalRuntimeSrc?: string | BootstrapScriptDescriptor,
 };
 
@@ -99,6 +100,7 @@ function prerenderToNodeStreams(
       undefined,
       undefined,
       onFatalError,
+      options ? options.onPostpone : undefined,
     );
     if (options && options.signal) {
       const signal = options.signal;

diff --git a/packages/react-dom/src/server/ReactDOMLegacyServerImpl.js b/packages/react-dom/src/server/ReactDOMLegacyServerImpl.js
@@ -79,6 +79,7 @@ function renderToStringImpl(
     onShellReady,
     undefined,
     undefined,
+    undefined,
   );
   startWork(request);
   // If anything suspended and is still pending, we'll abort it before writing.

diff --git a/packages/react-dom/src/server/ReactDOMLegacyServerNodeStream.js b/packages/react-dom/src/server/ReactDOMLegacyServerNodeStream.js
@@ -86,6 +86,7 @@ function renderToNodeStreamImpl(
     onAllReady,
     undefined,
     undefined,
+    undefined,
   );
   destination.request = request;
   startWork(request);

diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js
@@ -109,6 +109,7 @@ import {
   enableHostSingletons,
   enableFormActions,
   enableAsyncActions,
+  enablePostpone,
 } from 'shared/ReactFeatureFlags';
 import isArray from 'shared/isArray';
 import shallowEqual from 'shared/shallowEqual';
@@ -2867,19 +2868,23 @@ function updateDehydratedSuspenseComponent(
         ({digest} = getSuspenseInstanceFallbackErrorDetails(suspenseInstance));
       }
 
-      let error;
-      if (message) {
-        // eslint-disable-next-line react-internal/prod-error-codes
-        error = new Error(message);
-      } else {
-        error = new Error(
-          'The server could not finish this Suspense boundary, likely ' +
-            'due to an error during server rendering. Switched to ' +
-            'client rendering.',
-        );
+      let capturedValue = null;
+      // TODO: Figure out a better signal than encoding a magic digest value.
+      if (!enablePostpone || digest !== 'POSTPONE') {
+        let error;
+        if (message) {
+          // eslint-disable-next-line react-internal/prod-error-codes
+          error = new Error(message);
+        } else {
+          error = new Error(
+            'The server could not finish this Suspense boundary, likely ' +
+              'due to an error during server rendering. Switched to ' +
+              'client rendering.',
+          );
+        }
+        (error: any).digest = digest;
+        capturedValue = createCapturedValue<mixed>(error, digest, stack);
       }
-      (error: any).digest = digest;
-      const capturedValue = createCapturedValue<mixed>(error, digest, stack);
       return retrySuspenseComponentWithoutHydrating(
         current,
         workInProgress,