Serialize Error values

packages/react-client/src/ReactFlightClient.js

@@ -1287,6 +1287,21 @@ function parseModelString(
           createFormData,
         );
       }
+      case 'Z': {
+        // Error
+        if (__DEV__) {
+          const ref = value.slice(2);
+          return getOutlinedModel(
+            response,
+            ref,
+            parentObject,
+            key,
+            resolveErrorDev,
+          );
+        } else {
+          return resolveErrorProd(response);
+        }
+      }
       case 'i': {
         // Iterator
         const ref = value.slice(2);
@@ -1881,11 +1896,7 @@ function formatV8Stack(
 }
 
 type ErrorWithDigest = Error & {digest?: string};
-function resolveErrorProd(
-  response: Response,
-  id: number,
-  digest: string,
-): void {
+function resolveErrorProd(response: Response): Error {
   if (__DEV__) {
     // These errors should never make it into a build so we don't need to encode them in codes.json
     // eslint-disable-next-line react-internal/prod-error-codes
@@ -1899,25 +1910,17 @@ function resolveErrorProd(
       ' may provide additional details about the nature of the error.',
   );
   error.stack = 'Error: ' + error.message;
-  (error: any).digest = digest;
-  const errorWithDigest: ErrorWithDigest = (error: any);
-  const chunks = response._chunks;
-  const chunk = chunks.get(id);
-  if (!chunk) {
-    chunks.set(id, createErrorChunk(response, errorWithDigest));
-  } else {
-    triggerErrorOnChunk(chunk, errorWithDigest);
-  }
+  return error;
 }
 
 function resolveErrorDev(
   response: Response,
-  id: number,
-  digest: string,
-  message: string,
-  stack: ReactStackTrace,
-  env: string,
-): void {
+  errorInfo: {message: string, stack: ReactStackTrace, env: string, ...},
+): Error {
+  const message: string = errorInfo.message;
+  const stack: ReactStackTrace = errorInfo.stack;
+  const env: string = errorInfo.env;
+
   if (!__DEV__) {
     // These errors should never make it into a build so we don't need to encode them in codes.json
     // eslint-disable-next-line react-internal/prod-error-codes
@@ -1957,16 +1960,8 @@ function resolveErrorDev(
     }
   }
 
-  (error: any).digest = digest;
   (error: any).environmentName = env;
-  const errorWithDigest: ErrorWithDigest = (error: any);
-  const chunks = response._chunks;
-  const chunk = chunks.get(id);
-  if (!chunk) {
-    chunks.set(id, createErrorChunk(response, errorWithDigest));
-  } else {
-    triggerErrorOnChunk(chunk, errorWithDigest);
-  }
+  return error;
 }
 
 function resolvePostponeProd(response: Response, id: number): void {
@@ -2622,17 +2617,20 @@ function processFullStringRow(
     }
     case 69 /* "E" */: {
       const errorInfo = JSON.parse(row);
+      let error;
       if (__DEV__) {
-        resolveErrorDev(
-          response,
-          id,
-          errorInfo.digest,
-          errorInfo.message,
-          errorInfo.stack,
-          errorInfo.env,
-        );
+        error = resolveErrorDev(response, errorInfo);
+      } else {
+        error = resolveErrorProd(response);
+      }
+      (error: any).digest = errorInfo.digest;
+      const errorWithDigest: ErrorWithDigest = (error: any);
+      const chunks = response._chunks;
+      const chunk = chunks.get(id);
+      if (!chunk) {
+        chunks.set(id, createErrorChunk(response, errorWithDigest));
       } else {
-        resolveErrorProd(response, id, errorInfo.digest);
+        triggerErrorOnChunk(chunk, errorWithDigest);
       }
       return;
     }

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

@@ -653,6 +653,46 @@ describe('ReactFlight', () => {
       `);
   });
 
+  it('can transport Error objects as values', async () => {
+    function ComponentClient({prop}) {
+      return `
+        is error: ${prop instanceof Error}
+        message: ${prop.message}
+        stack: ${normalizeCodeLocInfo(prop.stack).split('\n').slice(0, 2).join('\n')}
+        environmentName: ${prop.environmentName}
+      `;
+    }
+    const Component = clientReference(ComponentClient);
+
+    function ServerComponent() {
+      const error = new Error('hello');
+      return <Component prop={error} />;
+    }
+
+    const transport = ReactNoopFlightServer.render(<ServerComponent />);
+
+    await act(async () => {
+      ReactNoop.render(await ReactNoopFlightClient.read(transport));
+    });
+
+    if (__DEV__) {
+      expect(ReactNoop).toMatchRenderedOutput(`
+        is error: true
+        message: hello
+        stack: Error: hello
+    in ServerComponent (at **)
+        environmentName: Server
+      `);
+    } else {
+      expect(ReactNoop).toMatchRenderedOutput(`
+        is error: true
+        message: An error occurred in the Server Components render. The specific message is omitted in production builds to avoid leaking sensitive details. A digest property is included on this error instance which may provide additional details about the nature of the error.
+        stack: Error: An error occurred in the Server Components render. The specific message is omitted in production builds to avoid leaking sensitive details. A digest property is included on this error instance which may provide additional details about the nature of the error.
+        environmentName: undefined
+      `);
+    }
+  });
+
   it('can transport cyclic objects', async () => {
     function ComponentClient({prop}) {
       expect(prop.obj.obj.obj).toBe(prop.obj.obj);

packages/react-server/src/ReactFlightServer.js

@@ -2688,6 +2688,9 @@ function renderModelDestructive(
     if (typeof FormData === 'function' && value instanceof FormData) {
       return serializeFormData(request, value);
     }
+    if (value instanceof Error) {
+      return serializeErrorValue(request, value);
+    }
 
     if (enableBinaryFlight) {
       if (value instanceof ArrayBuffer) {
@@ -3114,6 +3117,36 @@ function emitPostponeChunk(
   request.completedErrorChunks.push(processedChunk);
 }
 
+function serializeErrorValue(request: Request, error: Error): string {
+  if (__DEV__) {
+    let message;
+    let stack: ReactStackTrace;
+    let env = (0, request.environmentName)();
+    try {
+      // eslint-disable-next-line react-internal/safe-string-coercion
+      message = String(error.message);
+      stack = filterStackTrace(request, error, 0);
+      const errorEnv = (error: any).environmentName;
+      if (typeof errorEnv === 'string') {
+        // This probably came from another FlightClient as a pass through.
+        // Keep the environment name.
+        env = errorEnv;
+      }
+    } catch (x) {
+      message = 'An error occurred but serializing the error message failed.';
+      stack = [];
+    }
+    const errorInfo = {message, stack, env};
+    const id = outlineModel(request, errorInfo);
+    return '$Z' + id.toString(16);
+  } else {
+    // In prod we don't emit any information about this Error object to avoid
+    // unintentional leaks. Since this doesn't actually throw on the server
+    // we don't go through onError and so don't register any digest neither.
+    return '$Z';
+  }
+}
+
 function emitErrorChunk(
   request: Request,
   id: number,
@@ -3403,6 +3436,9 @@ function renderConsoleValue(
     if (typeof FormData === 'function' && value instanceof FormData) {
       return serializeFormData(request, value);
     }
+    if (value instanceof Error) {
+      return serializeErrorValue(request, value);
+    }
 
     if (enableBinaryFlight) {
       if (value instanceof ArrayBuffer) {