Fix ConcurrentModificationException in IntentModule.getInitialURL re-entrancy

[nickcernera]

Summary:

IntentModule.onHostResume() iterates pendingOpenURLPromises (an ArrayList) directly and calls getInitialURL() for each pending promise. When getCurrentActivity() returns null at that moment — e.g. a deep link or notification tap landing mid activity-transition during a rapid pause/resume — getInitialURL() re-enters waitForActivityAndGetInitialURL(), which calls pendingOpenURLPromises.add(promise) on the very list being iterated. The next iteration then throws java.util.ConcurrentModificationException:

java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1013)
at java.util.ArrayList$Itr.next(ArrayList.java:967)
at com.facebook.react.modules.intent.IntentModule$waitForActivityAndGetInitialURL$1.onHostResume(IntentModule.kt:90)

The synchronized(this@IntentModule) guard does not prevent this: the re-entrancy is on the same thread, which already holds the (reentrant) lock, so no second lock acquisition happens. The crash is the ArrayList iterator's modCount check, not a cross-thread race.

The fix snapshots the pending promises into a local copy, clears the shared list, and nulls the listener before draining. Re-queued promises then land in the now-empty pendingOpenURLPromises and register a fresh listener for the next resume, instead of mutating the list being iterated. Behaviour is otherwise unchanged.

Changelog:

[ANDROID] [FIXED] - Fix ConcurrentModificationException when getInitialURL re-enters during onHostResume

Test Plan:

Added IntentModuleTest.getInitialURL_onHostResumeWithNullActivity_doesNotThrowAndPreservesPromise, a Robolectric regression test that registers a pending promise while the current activity is null, then drives onHostResume so the drain re-queues, and asserts the drain does not throw and the promise is preserved (neither resolved nor rejected).

Ran locally against main with the exact reproduction scenario:

With the fix — passes:

$ ./gradlew :packages:react-native:ReactAndroid:testDebugUnitTest \
--tests "com.facebook.react.modules.intent.IntentModuleTest"
BUILD SUCCESSFUL
# tests=1, failures=0, errors=0

Without the fix (reverting IntentModule.kt only) — fails with the exact crash, confirming the test is a genuine regression test:

IntentModuleTest > getInitialURL_onHostResumeWithNullActivity_doesNotThrowAndPreservesPromise FAILED
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1013)
at java.util.ArrayList$Itr.next(ArrayList.java:967)
at com.facebook.react.modules.intent.IntentModule$waitForActivityAndGetInitialURL$1.onHostResume(IntentModule.kt:90)

ktfmt (Meta style, matching the repo's ktfmt configuration) reports both changed files as already formatted.

[meta-codesync]

@fabriziocucci has imported this pull request. If you are a Meta employee, you can view this in D113595327.

[cortinico]

Review automatically exported from Phabricator review in Meta.

[meta-codesync]

@fabriziocucci merged this pull request in 20d04ae.