Don't resume the new context without an Activity after a reload on Android (#59474)

Summary:
If the Activity is destroyed while a reload is still running, `ReactHostImpl` finishes the reload by calling `moveToOnHostResume(reactContext, currentActivity)` with `currentActivity` already null. The new context gets `onHostResume(null)` and the lifecycle state becomes `RESUMED`, so when the app is reopened `onHostResume(activity)` returns early and `getCurrentActivity()` stays null until the next pause/resume. That's what makes `PermissionsAndroid.request()` reject with `E_INVALID_ACTIVITY` (and likely the `Alert` error in #46201).

The reload branch now only resumes the context when there is an Activity. Otherwise it falls through to the normal path, and the next `onHostResume(activity)` resumes the context with the right Activity.

Fixes #59473

## Changelog:

[ANDROID] [FIXED] - Fix `getCurrentActivity()` staying null after the Activity is destroyed during a reload

Pull Request resolved: #59474

Test Plan: Added `ReactHostTest.testActivityDestroyedDuringReload`. It queues background work so the Activity can be paused and destroyed before the reload finishes, then resumes a new Activity and checks the new context gets it. On `main` it fails (state is `RESUMED` and the context only got `onHostResume(null)`), and it passes with this change. `./gradlew :packages:react-native:ReactAndroid:testDebugUnitTest` passes and ktfmt is clean. I didn't run the reproducer on a device.

Reviewed By: christophpurrer

Differential Revision: D127564742

Pulled By: javache

fbshipit-source-id: 37a80ed86e799473bfc6ed251f60c5ae58506772

Author: lazerg

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/runtime/ReactHostImpl.kt

@@ -1109,7 +1109,7 @@ public class ReactHostImpl(
          * Native is reloading, it seems reasonable to assume that: (1) We must have navigated to a
          * React Native screen in the past, or (2) We must be on a React Native screen.
          */
-        if (isReloading && !isManagerResumed) {
+        if (isReloading && !isManagerResumed && currentActivity != null) {
           reactLifecycleStateManager.moveToOnHostResume(reactContext, currentActivity)
         } else {
           /**

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/runtime/ReactHostTest.kt

@@ -168,4 +168,38 @@ class ReactHostTest {
     reactHost.onHostDestroy(activityController.get())
     assertThat(reactHost.lifecycleState).isEqualTo(LifecycleState.BEFORE_CREATE)
   }
+
+  @Test
+  fun testActivityDestroyedDuringReload() {
+    val bgTasks = ArrayDeque<Runnable>()
+    reactHost =
+        spy(
+            ReactHostImpl(
+                activityController.get().application,
+                reactHostDelegate,
+                mock(),
+                { bgTasks.add(it) },
+                Task.IMMEDIATE_EXECUTOR,
+                false /* allowPackagerServerAccess */,
+                false /* useDevSupport */,
+            ),
+        )
+    doReturn(null).whenever(reactHost).getOrCreateReactHostInspectorTarget()
+    doNothing().whenever(reactHost).unregisterInstanceFromInspector(any())
+
+    reactHost.start()
+    while (bgTasks.isNotEmpty()) bgTasks.removeFirst().run()
+    reactHost.onHostResume(activityController.get())
+
+    reactHost.reload("Reload from testing infra")
+    reactHost.onHostPause(activityController.get())
+    reactHost.onHostDestroy(activityController.get())
+    while (bgTasks.isNotEmpty()) bgTasks.removeFirst().run()
+    assertThat(reactHost.lifecycleState).isEqualTo(LifecycleState.BEFORE_CREATE)
+
+    val newActivity = Robolectric.buildActivity(Activity::class.java).create().start().resume()
+    reactHost.onHostResume(newActivity.get())
+    val newReactContext = mockedBridgelessReactContextCtor.constructed().last()
+    verify(newReactContext).onHostResume(newActivity.get())
+  }
 }