fix(react-router-dom): Fix usePrompt invalid blocker state transition

.changeset/prompt-effect-order.md

@@ -0,0 +1,5 @@
+---
+"react-router-dom": patch
+---
+
+Reorder effects in `unstable_usePrompt` to avoid throwing an exception if the prompt is unblocked and a navigation is performed syncronously

contributors.yml

@@ -223,3 +223,4 @@
 - yuleicul
 - zheng-chuang
 - istarkov
+- louis-young

packages/react-router-dom/__tests__/use-prompt-test.tsx

@@ -0,0 +1,126 @@
+import * as React from "react";
+import { fireEvent, render, screen, waitFor } from "@testing-library/react";
+import {
+  Link,
+  RouterProvider,
+  createBrowserRouter,
+  unstable_usePrompt as usePrompt,
+} from "../index";
+import "@testing-library/jest-dom";
+import { JSDOM } from "jsdom";
+
+describe("usePrompt", () => {
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe("when navigation is blocked", () => {
+    it("shows window.confirm and blocks navigation when it returns false", async () => {
+      let testWindow = getWindowImpl("/");
+      const windowConfirmMock = jest
+        .spyOn(window, "confirm")
+        .mockImplementationOnce(() => false);
+
+      let router = createBrowserRouter(
+        [
+          {
+            path: "/",
+            Component() {
+              usePrompt({ when: true, message: "Are you sure??" });
+              return <Link to="/arbitrary">Navigate</Link>;
+            },
+          },
+          {
+            path: "/arbitrary",
+            Component: () => <h1>Arbitrary</h1>,
+          },
+        ],
+        { window: testWindow }
+      );
+
+      render(<RouterProvider router={router} />);
+      expect(screen.getByText("Navigate")).toBeInTheDocument();
+
+      fireEvent.click(screen.getByText("Navigate"));
+      await new Promise((r) => setTimeout(r, 0));
+
+      expect(windowConfirmMock).toHaveBeenNthCalledWith(1, "Are you sure??");
+      expect(screen.getByText("Navigate")).toBeInTheDocument();
+    });
+
+    it("shows window.confirm and navigates when it returns true", async () => {
+      let testWindow = getWindowImpl("/");
+      const windowConfirmMock = jest
+        .spyOn(window, "confirm")
+        .mockImplementationOnce(() => true);
+
+      let router = createBrowserRouter(
+        [
+          {
+            path: "/",
+            Component() {
+              usePrompt({ when: true, message: "Are you sure??" });
+              return <Link to="/arbitrary">Navigate</Link>;
+            },
+          },
+          {
+            path: "/arbitrary",
+            Component: () => <h1>Arbitrary</h1>,
+          },
+        ],
+        { window: testWindow }
+      );
+
+      render(<RouterProvider router={router} />);
+      expect(screen.getByText("Navigate")).toBeInTheDocument();
+
+      fireEvent.click(screen.getByText("Navigate"));
+      await waitFor(() => screen.getByText("Arbitrary"));
+
+      expect(windowConfirmMock).toHaveBeenNthCalledWith(1, "Are you sure??");
+      expect(screen.getByText("Arbitrary")).toBeInTheDocument();
+    });
+  });
+
+  describe("when navigation is not blocked", () => {
+    it("navigates without showing window.confirm", async () => {
+      let testWindow = getWindowImpl("/");
+      const windowConfirmMock = jest
+        .spyOn(window, "confirm")
+        .mockImplementation(() => true);
+
+      let router = createBrowserRouter(
+        [
+          {
+            path: "/",
+            Component() {
+              usePrompt({ when: false, message: "Are you sure??" });
+              return <Link to="/arbitrary">Navigate</Link>;
+            },
+          },
+          {
+            path: "/arbitrary",
+            Component: () => <h1>Arbitrary</h1>,
+          },
+        ],
+        { window: testWindow }
+      );
+
+      render(<RouterProvider router={router} />);
+      expect(screen.getByText("Navigate")).toBeInTheDocument();
+
+      fireEvent.click(screen.getByText("Navigate"));
+      await waitFor(() => screen.getByText("Arbitrary"));
+
+      expect(windowConfirmMock).not.toHaveBeenCalled();
+      expect(screen.getByText("Arbitrary")).toBeInTheDocument();
+    });
+  });
+});
+
+function getWindowImpl(initialUrl: string, isHash = false): Window {
+  // Need to use our own custom DOM in order to get a working history
+  const dom = new JSDOM(`<!DOCTYPE html>`, { url: "http://localhost/" });
+  dom.window.history.replaceState(null, "", (isHash ? "#" : "") + initialUrl);
+  return dom.window as unknown as Window;
+}

packages/react-router-dom/index.tsx

@@ -1461,22 +1461,22 @@ function usePageHide(
 function usePrompt({ when, message }: { when: boolean; message: string }) {
   let blocker = useBlocker(when);
 
-  React.useEffect(() => {
-    if (blocker.state === "blocked" && !when) {
-      blocker.reset();
-    }
-  }, [blocker, when]);
-
   React.useEffect(() => {
     if (blocker.state === "blocked") {
       let proceed = window.confirm(message);
       if (proceed) {
-        setTimeout(blocker.proceed, 0);
+        blocker.proceed();
       } else {
         blocker.reset();
       }
     }
   }, [blocker, message]);
+
+  React.useEffect(() => {
+    if (blocker.state === "blocked" && !when) {
+      blocker.reset();
+    }
+  }, [blocker, when]);
 }
 
 export { usePrompt as unstable_usePrompt };