Expo Router integration improvement: Prefetch route performance measurement with automatically created spans (#5606)

* Expo Router improvement: Prefetch route performance measurement with automatically created spans

* Performance measurement for manual expo router prefetch() call

* Changelog entry with the usage example

* Fix

* `sentry.origin` added, tests adjusted

* File renamed

* Test fixes

* Lint fix

Author: alwx

CHANGELOG.md

@@ -8,6 +8,29 @@
 
 ## Unreleased
 
+### Features
+
+- Add performance tracking for Expo Router route prefetching ([#5606](https://github.com/getsentry/sentry-react-native/pull/5606))
+  - New `wrapExpoRouter` utility to instrument manual `prefetch()` calls with performance spans
+  - New `enablePrefetchTracking` option for `reactNavigationIntegration` to automatically track PRELOAD actions
+  ```tsx
+  // Option 1: Wrap the router for manual prefetch tracking
+  import { wrapExpoRouter } from '@sentry/react-native';
+  import { useRouter } from 'expo-router';
+
+  const router = wrapExpoRouter(useRouter());
+  router.prefetch('/details'); // Creates a span measuring prefetch performance
+
+  // Option 2: Enable automatic prefetch tracking in the integration
+  Sentry.init({
+    integrations: [
+      Sentry.reactNavigationIntegration({
+        enablePrefetchTracking: true,
+      }),
+    ],
+  });
+  ```
+
 ### Dependencies
 
 - Bump JavaScript SDK from v10.37.0 to v10.38.0 ([#5596](https://github.com/getsentry/sentry-react-native/pull/5596))

packages/core/src/js/index.ts

@@ -91,9 +91,10 @@ export {
   getDefaultIdleNavigationSpanOptions,
   createTimeToFullDisplay,
   createTimeToInitialDisplay,
+  wrapExpoRouter,
 } from './tracing';
 
-export type { TimeToDisplayProps } from './tracing';
+export type { TimeToDisplayProps, ExpoRouter } from './tracing';
 
 export { Mask, Unmask } from './replay/CustomMask';
 

packages/core/src/js/tracing/expoRouter.ts

@@ -0,0 +1,90 @@
+import { SPAN_STATUS_ERROR, SPAN_STATUS_OK, startInactiveSpan } from '@sentry/core';
+import { SPAN_ORIGIN_AUTO_EXPO_ROUTER_PREFETCH } from './origin';
+
+/**
+ * Type definition for Expo Router's router object
+ */
+export interface ExpoRouter {
+  prefetch?: (href: string | { pathname?: string; params?: Record<string, unknown> }) => void | Promise<void>;
+  // Other router methods can be added here if needed
+  push?: (...args: unknown[]) => void;
+  replace?: (...args: unknown[]) => void;
+  back?: () => void;
+  navigate?: (...args: unknown[]) => void;
+}
+
+/**
+ * Wraps Expo Router. It currently only does one thing: extends prefetch() method
+ * to add automated performance monitoring.
+ *
+ * This function instruments the `prefetch` method of an Expo Router instance
+ * to create performance spans that measure how long route prefetching takes.
+ *
+ * @param router - The Expo Router instance from `useRouter()` hook
+ * @returns The same router instance with an instrumented prefetch method
+ */
+export function wrapExpoRouter<T extends ExpoRouter>(router: T): T {
+  if (!router?.prefetch) {
+    return router;
+  }
+
+  // Check if already wrapped to avoid double-wrapping
+  if ((router as T & { __sentryPrefetchWrapped?: boolean }).__sentryPrefetchWrapped) {
+    return router;
+  }
+
+  const originalPrefetch = router.prefetch.bind(router);
+
+  router.prefetch = ((href: Parameters<NonNullable<ExpoRouter['prefetch']>>[0]) => {
+    // Extract route name from href for better span naming
+    let routeName = 'unknown';
+    if (typeof href === 'string') {
+      routeName = href;
+    } else if (href && typeof href === 'object' && 'pathname' in href && href.pathname) {
+      routeName = href.pathname;
+    }
+
+    const span = startInactiveSpan({
+      op: 'navigation.prefetch',
+      name: `Prefetch ${routeName}`,
+      attributes: {
+        'sentry.origin': SPAN_ORIGIN_AUTO_EXPO_ROUTER_PREFETCH,
+        'route.href': typeof href === 'string' ? href : JSON.stringify(href),
+        'route.name': routeName,
+      },
+    });
+
+    try {
+      const result = originalPrefetch(href);
+
+      // Handle both promise and synchronous returns
+      if (result && typeof result === 'object' && 'then' in result && typeof result.then === 'function') {
+        return result
+          .then(res => {
+            span?.setStatus({ code: SPAN_STATUS_OK });
+            span?.end();
+            return res;
+          })
+          .catch((error: unknown) => {
+            span?.setStatus({ code: SPAN_STATUS_ERROR, message: String(error) });
+            span?.end();
+            throw error;
+          });
+      } else {
+        // Synchronous completion
+        span?.setStatus({ code: SPAN_STATUS_OK });
+        span?.end();
+        return result;
+      }
+    } catch (error) {
+      span?.setStatus({ code: SPAN_STATUS_ERROR, message: String(error) });
+      span?.end();
+      throw error;
+    }
+  }) as NonNullable<T['prefetch']>;
+
+  // Mark as wrapped to prevent double-wrapping
+  (router as T & { __sentryPrefetchWrapped?: boolean }).__sentryPrefetchWrapped = true;
+
+  return router;
+}

packages/core/src/js/tracing/index.ts

@@ -9,6 +9,9 @@ export type { ReactNativeTracingIntegration } from './reactnativetracing';
 export { reactNavigationIntegration } from './reactnavigation';
 export { reactNativeNavigationIntegration } from './reactnativenavigation';
 
+export { wrapExpoRouter } from './expoRouter';
+export type { ExpoRouter } from './expoRouter';
+
 export { startIdleNavigationSpan, startIdleSpan, getDefaultIdleNavigationSpanOptions } from './span';
 
 export type { ReactNavigationCurrentRoute, ReactNavigationRoute } from './types';

packages/core/src/js/tracing/origin.ts

@@ -10,3 +10,5 @@ export const SPAN_ORIGIN_AUTO_NAVIGATION_CUSTOM = 'auto.navigation.custom';
 
 export const SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY = 'auto.ui.time_to_display';
 export const SPAN_ORIGIN_MANUAL_UI_TIME_TO_DISPLAY = 'manual.ui.time_to_display';
+
+export const SPAN_ORIGIN_AUTO_EXPO_ROUTER_PREFETCH = 'auto.expo_router.prefetch';

packages/core/src/js/tracing/reactnavigation.ts

@@ -104,6 +104,15 @@ interface ReactNavigationIntegrationOptions {
    * @default false
    */
   useFullPathsForNavigationRoutes: boolean;
+
+  /**
+   * Track performance of route prefetching operations.
+   * Creates separate spans for PRELOAD actions to measure prefetch performance.
+   * This is useful for Expo Router apps that use the prefetch functionality.
+   *
+   * @default false
+   */
+  enablePrefetchTracking: boolean;
 }
 
 /**
@@ -121,6 +130,7 @@ export const reactNavigationIntegration = ({
   enableTimeToInitialDisplayForPreloadedRoutes = false,
   useDispatchedActionData = false,
   useFullPathsForNavigationRoutes = false,
+  enablePrefetchTracking = false,
 }: Partial<ReactNavigationIntegrationOptions> = {}): Integration & {
   /**
    * Pass the ref to the navigation container to register it to the instrumentation
@@ -253,12 +263,48 @@ export const reactNavigationIntegration = ({
     }
 
     const navigationActionType = useDispatchedActionData ? event?.data.action.type : undefined;
+
+    // Handle PRELOAD actions separately if prefetch tracking is enabled
+    if (enablePrefetchTracking && navigationActionType === 'PRELOAD') {
+      const preloadData = event?.data.action;
+      const payload = preloadData?.payload;
+      const targetRoute =
+        payload && typeof payload === 'object' && 'name' in payload && typeof payload.name === 'string'
+          ? payload.name
+          : 'Unknown Route';
+
+      debug.log(`${INTEGRATION_NAME} Starting prefetch span for route: ${targetRoute}`);
+
+      const prefetchSpan = startInactiveSpan({
+        op: 'navigation.prefetch',
+        name: `Prefetch ${targetRoute}`,
+        attributes: {
+          'route.name': targetRoute,
+        },
+      });
+
+      // Store prefetch span to end it when state changes or timeout
+      navigationProcessingSpan = prefetchSpan;
+
+      // Set timeout to ensure we don't leave hanging spans
+      stateChangeTimeout = setTimeout(() => {
+        if (navigationProcessingSpan === prefetchSpan) {
+          debug.log(`${INTEGRATION_NAME} Prefetch span timed out for route: ${targetRoute}`);
+          prefetchSpan?.setStatus({ code: SPAN_STATUS_OK });
+          prefetchSpan?.end();
+          navigationProcessingSpan = undefined;
+        }
+      }, routeChangeTimeoutMs);
+
+      return;
+    }
+
     if (
       useDispatchedActionData &&
       navigationActionType &&
       [
         // Process common actions
-        'PRELOAD',
+        'PRELOAD', // Still filter PRELOAD when enablePrefetchTracking is false
         'SET_PARAMS',
         // Drawer actions
         'OPEN_DRAWER',
@@ -447,6 +493,7 @@ export const reactNavigationIntegration = ({
       enableTimeToInitialDisplayForPreloadedRoutes,
       useDispatchedActionData,
       useFullPathsForNavigationRoutes,
+      enablePrefetchTracking,
     },
   };
 };