fix(theme-classic): fix breadcrumb home link bug with new useHomePageRoute() hook (#6749)

packages/docusaurus-theme-common/src/index.ts

@@ -124,6 +124,8 @@ export {
 
 export {isRegexpStringMatch} from './utils/regexpUtils';
 
+export {useHomePageRoute} from './utils/routesUtils';
+
 export {useColorMode, ColorModeProvider} from './utils/colorModeUtils';
 export {
   useTabGroupChoice,

packages/docusaurus-theme-common/src/utils/__tests__/routesUtils.test.ts

@@ -0,0 +1,73 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {type Route} from '@generated/routes';
+import {findHomePageRoute} from '../routesUtils';
+
+describe('routesUtils findHomePageRoute', () => {
+  const homePage: Route = {
+    path: '/',
+    exact: true,
+  };
+
+  test('should return undefined for no routes', () => {
+    expect(findHomePageRoute([])).toEqual(undefined);
+  });
+
+  test('should return undefined for no homepage', () => {
+    expect(
+      findHomePageRoute([
+        {path: '/a', exact: true},
+        {path: '/b', exact: false},
+        {path: '/c', exact: undefined},
+        {
+          path: '/d',
+          exact: false,
+          routes: [
+            {path: '/d/1', exact: true},
+            {path: '/d/2', exact: false},
+            {path: '/d/3', exact: undefined},
+          ],
+        },
+      ]),
+    ).toEqual(undefined);
+  });
+
+  test('should find top-level homepage', () => {
+    expect(
+      findHomePageRoute([
+        {path: '/a', exact: true},
+        {path: '/b', exact: false},
+        {path: '/c', exact: undefined},
+        {...homePage, exact: false},
+        homePage,
+        {...homePage, exact: undefined},
+      ]),
+    ).toEqual(homePage);
+  });
+
+  test('should find nested homepage', () => {
+    expect(
+      findHomePageRoute([
+        {path: '/a', exact: true},
+        {
+          path: '/',
+          exact: false,
+          routes: [
+            {path: '/b', exact: true},
+            {
+              path: '/',
+              exact: false,
+              routes: [{path: '/c', exact: true}, homePage],
+            },
+          ],
+        },
+        {path: '/d', exact: true},
+      ]),
+    ).toEqual(homePage);
+  });
+});

packages/docusaurus-theme-common/src/utils/routesUtils.ts

@@ -0,0 +1,39 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import GeneratedRoutes, {type Route} from '@generated/routes';
+import {useMemo} from 'react';
+
+function isHomePageRoute(route: Route): boolean {
+  return route.path === '/' && route.exact === true;
+}
+
+function isHomeParentRoute(route: Route): boolean {
+  return route.path === '/' && route.exact === false;
+}
+
+// Note that all sites don't always have a homepage in practice
+// See https://github.com/facebook/docusaurus/pull/6517#issuecomment-1048709116
+export function findHomePageRoute(
+  routes: Route[] = GeneratedRoutes,
+): Route | undefined {
+  if (routes.length === 0) {
+    return undefined;
+  }
+  const homePage = routes.find(isHomePageRoute);
+  if (homePage) {
+    return homePage;
+  }
+  const indexSubRoutes = routes
+    .filter(isHomeParentRoute)
+    .flatMap((route) => route.routes ?? []);
+  return findHomePageRoute(indexSubRoutes);
+}
+
+export function useHomePageRoute(): Route | undefined {
+  return useMemo(() => findHomePageRoute(), []);
+}