fix(requestIdleCallback): timeout not assigned at NativeIdleCallbacks

gradle.properties

@@ -13,7 +13,7 @@ reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64
 # Controls whether to use Hermes from stable builds. This will force hermes version
 # set in the sdks/hermes-engine/version.properties file to be used. This has a higher
 # priority than react.internal.useHermesNightly.
-react.internal.useHermesStable=false
+react.internal.useHermesStable=true
 
 # Controls whether to use Hermes from nightly builds. This will speed up builds
 # but should NOT be turned on for CI or release builds.

packages/react-native/ReactCommon/react/nativemodule/idlecallbacks/NativeIdleCallbacks.cpp

@@ -87,6 +87,7 @@ CallbackHandle NativeIdleCallbacks::requestIdleCallback(
   if (options.has_value() && options.value().timeout.has_value()) {
     HighResDuration userTimeout = options.value().timeout.value();
     if (userTimeout > HighResDuration::zero()) {
+      timeout = userTimeout;
       expirationTime = runtimeScheduler->now() + userTimeout;
     }
   }

packages/rn-tester/js/examples/Playground/RNTesterPlayground.js

@@ -13,13 +13,63 @@ import type {RNTesterModuleExample} from '../../types/RNTesterTypes';
 import RNTesterText from '../../components/RNTesterText';
 import * as React from 'react';
 import {StyleSheet, View} from 'react-native';
+import {useState, useEffect} from 'react';
 
+/**
+ * Proves NativeIdleCallbacks forwards options.timeout into scheduleIdleTask.
+ *
+ * Strategy: keep scheduling LowPriority work (10s expiry each). That always
+ * beats an idle task with the default 5min expiry (bug), but after the first
+ * LowPriority tick a patched idle task (LowPriority + timeout ≈ 10s) becomes
+ * the earliest-expiring task and runs.
+ *
+ * Expect with the patch: fire within ~1s.
+ * Expect without (`timeout = userTimeout` removed): stuck on "starving…" for minutes.
+ */
 function Playground() {
+  const [label, setLabel] = useState('starving LowPriority queue…');
+
+  useEffect(() => {
+    const scheduler = global.nativeRuntimeScheduler;
+    const {unstable_scheduleCallback, unstable_LowPriority} = scheduler;
+
+    const start = performance.now();
+    let keepStarving = true;
+
+    const starve = () => {
+      if (!keepStarving) {
+        return;
+      }
+      unstable_scheduleCallback(unstable_LowPriority, () => {
+        const blockStart = performance.now();
+        while (performance.now() - blockStart < 30) {}
+        starve();
+      });
+    };
+
+    requestIdleCallback(
+      deadline => {
+        keepStarving = false;
+        const elapsedMs = Math.round(performance.now() - start);
+        setLabel(
+          `✅ PATCHED: fired after ${elapsedMs}ms under LowPriority load, didTimeout=${String(
+            deadline.didTimeout,
+          )}`,
+        );
+      },
+      {timeout: 10},
+    );
+
+    starve();
+
+    return () => {
+      keepStarving = false;
+    };
+  }, []);
+
   return (
     <View style={styles.container}>
-      <RNTesterText>
-        Edit "RNTesterPlayground.js" to change this file
-      </RNTesterText>
+      <RNTesterText>{label}</RNTesterText>
     </View>
   );
 }