Hydrate proper error type for subclasses of Error

.changeset/hydrate-error-type.md

@@ -0,0 +1,5 @@
+---
+"react-router-dom": patch
+---
+
+Support proper hydration of `Error` subclasses such as `ReferenceError`/`TypeError`

package.json

@@ -118,10 +118,10 @@
       "none": "16.2 kB"
     },
     "packages/react-router-dom/dist/react-router-dom.production.min.js": {
-      "none": "12.6 kB"
+      "none": "12.7 kB"
     },
     "packages/react-router-dom/dist/umd/react-router-dom.production.min.js": {
-      "none": "18.6 kB"
+      "none": "18.7 kB"
     }
   }
 }

packages/react-router-dom/__tests__/data-browser-router-test.tsx

@@ -328,6 +328,49 @@ function testDomRouter(
       `);
     });
 
+    it("deserializes Error subclass instances from the window", async () => {
+      window.__staticRouterHydrationData = {
+        loaderData: {},
+        actionData: null,
+        errors: {
+          "0": {
+            message: "error message",
+            __type: "Error",
+            __subType: "ReferenceError",
+          },
+        },
+      };
+      let router = createTestRouter(
+        createRoutesFromElements(
+          <Route path="/" element={<h1>Nope</h1>} errorElement={<Boundary />} />
+        )
+      );
+      let { container } = render(<RouterProvider router={router} />);
+
+      function Boundary() {
+        let error = useRouteError() as Error;
+        return error instanceof Error ? (
+          <>
+            <pre>{error.toString()}</pre>
+            <pre>stack:{error.stack}</pre>
+          </>
+        ) : (
+          <p>No :(</p>
+        );
+      }
+
+      expect(getHtml(container)).toMatchInlineSnapshot(`
+        "<div>
+          <pre>
+            ReferenceError: error message
+          </pre>
+          <pre>
+            stack:
+          </pre>
+        </div>"
+      `);
+    });
+
     it("renders fallbackElement while first data fetch happens", async () => {
       let fooDefer = createDeferred();
       let router = createTestRouter(

packages/react-router-dom/__tests__/data-static-router-test.tsx

@@ -701,6 +701,51 @@ describe("A <StaticRouterProvider>", () => {
     );
   });
 
+  it("serializes Error subclass instances", async () => {
+    let routes = [
+      {
+        path: "/",
+        loader: () => {
+          throw new ReferenceError("oh no");
+        },
+      },
+    ];
+    let { query } = createStaticHandler(routes);
+
+    let context = (await query(
+      new Request("http://localhost/", {
+        signal: new AbortController().signal,
+      })
+    )) as StaticHandlerContext;
+
+    let html = ReactDOMServer.renderToStaticMarkup(
+      <React.StrictMode>
+        <StaticRouterProvider
+          router={createStaticRouter(routes, context)}
+          context={context}
+        />
+      </React.StrictMode>
+    );
+
+    // stack is stripped by default from SSR errors
+    let expectedJsonString = JSON.stringify(
+      JSON.stringify({
+        loaderData: {},
+        actionData: null,
+        errors: {
+          "0": {
+            message: "oh no",
+            __type: "Error",
+            __subType: "ReferenceError",
+          },
+        },
+      })
+    );
+    expect(html).toMatch(
+      `<script>window.__staticRouterHydrationData = JSON.parse(${expectedJsonString});</script>`
+    );
+  });
+
   it("supports a nonce prop", async () => {
     let routes = [
       {

packages/react-router-dom/index.tsx

@@ -278,11 +278,30 @@ function deserializeErrors(
         val.internal === true
       );
     } else if (val && val.__type === "Error") {
-      let error = new Error(val.message);
-      // Wipe away the client-side stack trace.  Nothing to fill it in with
-      // because we don't serialize SSR stack traces for security reasons
-      error.stack = "";
-      serialized[key] = error;
+      // Attempt to reconstruct the right type of Error (i.e., ReferenceError)
+      if (val.__subType) {
+        let ErrorConstructor = window[val.__subType];
+        if (typeof ErrorConstructor === "function") {
+          try {
+            // @ts-expect-error
+            let error = new ErrorConstructor(val.message);
+            // Wipe away the client-side stack trace.  Nothing to fill it in with
+            // because we don't serialize SSR stack traces for security reasons
+            error.stack = "";
+            serialized[key] = error;
+          } catch (e) {
+            // no-op - fall through and create a normal Error
+          }
+        }
+      }
+
+      if (serialized[key] == null) {
+        let error = new Error(val.message);
+        // Wipe away the client-side stack trace.  Nothing to fill it in with
+        // because we don't serialize SSR stack traces for security reasons
+        error.stack = "";
+        serialized[key] = error;
+      }
     } else {
       serialized[key] = val;
     }

packages/react-router-dom/server.tsx

@@ -179,6 +179,13 @@ function serializeErrors(
       serialized[key] = {
         message: val.message,
         __type: "Error",
+        // If this is a subclass (i.e., ReferenceError), send up the type so we
+        // can re-create the same type during hydration.
+        ...(val.name !== "Error"
+          ? {
+              __subType: val.name,
+            }
+          : {}),
       };
     } else {
       serialized[key] = val;