Implement Navigation API backed default indicator

Author: sebmarkbage

packages/react-dom/src/client/ReactDOMDefaultTransitionIndicator.js

@@ -0,0 +1,89 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+export function defaultOnDefaultTransitionIndicator(): void | (() => void) {
+  if (typeof navigation !== 'object') {
+    // If the Navigation API is not available, then this is a noop.
+    return;
+  }
+
+  let isCancelled = false;
+  let pendingResolve: null | (() => void) = null;
+
+  function handleNavigate(event: NavigateEvent) {
+    if (event.canIntercept && event.info === 'react-transition') {
+      event.intercept({
+        handler() {
+          return new Promise(resolve => (pendingResolve = resolve));
+        },
+        focusReset: 'manual',
+        scroll: 'manual',
+      });
+    }
+  }
+
+  function handleNavigateComplete() {
+    if (pendingResolve !== null) {
+      // If this was not our navigation completing, we were probably cancelled.
+      // We'll start a new one below.
+      pendingResolve();
+      pendingResolve = null;
+    }
+    if (!isCancelled) {
+      // Some other navigation completed but we should still be running.
+      // Start another fake one to keep the loading indicator going.
+      startFakeNavigation();
+    }
+  }
+
+  // $FlowFixMe
+  navigation.addEventListener('navigate', handleNavigate);
+  // $FlowFixMe
+  navigation.addEventListener('navigatesuccess', handleNavigateComplete);
+  // $FlowFixMe
+  navigation.addEventListener('navigateerror', handleNavigateComplete);
+
+  function startFakeNavigation() {
+    if (isCancelled) {
+      // We already stopped this Transition.
+      return;
+    }
+    if (navigation.transition) {
+      // There is an on-going Navigation already happening. Let's wait for it to
+      // finish before starting our fake one.
+      return;
+    }
+    // Trigger a fake navigation to the same page
+    const currentEntry = navigation.currentEntry;
+    if (currentEntry && currentEntry.url != null) {
+      navigation.navigate(currentEntry.url, {
+        state: currentEntry.getState(),
+        info: 'react-transition', // indicator to routers to ignore this navigation
+        history: 'replace',
+      });
+    }
+  }
+
+  // Delay the start a bit in case this is a fast navigation.
+  setTimeout(startFakeNavigation, 100);
+
+  return function () {
+    isCancelled = true;
+    // $FlowFixMe
+    navigation.removeEventListener('navigate', handleNavigate);
+    // $FlowFixMe
+    navigation.removeEventListener('navigatesuccess', handleNavigateComplete);
+    // $FlowFixMe
+    navigation.removeEventListener('navigateerror', handleNavigateComplete);
+    if (pendingResolve !== null) {
+      pendingResolve();
+      pendingResolve = null;
+    }
+  };
+}

packages/react-dom/src/client/ReactDOMRoot.js

@@ -95,13 +95,9 @@ import {
   defaultOnCaughtError,
   defaultOnRecoverableError,
 } from 'react-reconciler/src/ReactFiberReconciler';
+import {defaultOnDefaultTransitionIndicator} from './ReactDOMDefaultTransitionIndicator';
 import {ConcurrentRoot} from 'react-reconciler/src/ReactRootTags';
 
-function defaultOnDefaultTransitionIndicator(): void | (() => void) {
-  // TODO: Implement the default
-  return function () {};
-}
-
 // $FlowFixMe[missing-this-annot]
 function ReactDOMRoot(internalRoot: FiberRoot) {
   this._internalRoot = internalRoot;