Fix concurrent modification (#986)

Snapshot collections with .toList() / List.of() before iterating,
preventing modification by concurrent async event handlers.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Fixed potential concurrent modification exceptions that could occur
during async operations when iterating over participant data, event
listeners, and audio elements.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: hiroshihorie

.changes/fix-concurrent-modification

@@ -0,0 +1 @@
+patch type="fixed" "Fix concurrent modification on collection iteration during async operations"

lib/src/core/room.dart

@@ -539,8 +539,8 @@ class Room extends DisposableChangeNotifier with EventsEmittable<RoomEvent> {
       // re-publish all tracks
       await localParticipant?.rePublishAllTracks();
 
-      for (var participant in _remoteParticipants) {
-        for (var pub in participant.trackPublications.values) {
+      for (var participant in _remoteParticipants.toList()) {
+        for (var pub in participant.trackPublications.values.toList()) {
           if (pub.subscribed) {
             pub.sendUpdateTrackSettings();
           }
@@ -936,8 +936,8 @@ class Room extends DisposableChangeNotifier with EventsEmittable<RoomEvent> {
     final trackSids = <String>[];
     final trackSidsDisabled = <String>[];
 
-    for (var participant in _remoteParticipants) {
-      for (var track in participant.trackPublications.values) {
+    for (var participant in _remoteParticipants.toList()) {
+      for (var track in participant.trackPublications.values.toList()) {
         if (track.subscribed != autoSubscribe) {
           trackSids.add(track.sid);
         }
@@ -1084,7 +1084,7 @@ extension RoomHardwareManagementMethods on Room {
   /// Set audio output device.
   Future<void> setAudioOutputDevice(MediaDevice device) async {
     if (lkPlatformIs(PlatformType.web)) {
-      for (final participant in _remoteParticipants) {
+      for (final participant in _remoteParticipants.toList()) {
         for (final audioTrack in participant.audioTrackPublications) {
           audioTrack.track?.setSinkId(device.deviceId);
         }

lib/src/core/signal_client.dart

@@ -517,10 +517,11 @@ extension SignalClientInternalMethods on SignalClient {
     // queue is empty
     if (_queue.isEmpty) return;
     // send requests
-    for (final request in _queue) {
+    final queueCopy = List.of(_queue);
+    _queue.clear();
+    for (final request in queueCopy) {
       _sendRequest(request, enqueueIfReconnecting: false);
     }
-    _queue.clear();
   }
 
   @internal

lib/src/e2ee/e2ee_manager.dart

@@ -141,7 +141,7 @@ class E2EEManager {
     await _listener?.cancelAll();
     await _listener?.dispose();
     _listener = null;
-    for (var frameCryptor in _frameCryptors.values) {
+    for (var frameCryptor in _frameCryptors.values.toList()) {
       await frameCryptor.dispose();
     }
     _frameCryptors.clear();
@@ -178,7 +178,7 @@ class E2EEManager {
   /// without encryption/decryption
   Future<void> setEnabled(bool enabled) async {
     _enabled = enabled;
-    for (var frameCryptor in _frameCryptors.entries) {
+    for (var frameCryptor in _frameCryptors.entries.toList()) {
       await frameCryptor.value.setEnabled(enabled);
     }
   }
@@ -189,7 +189,7 @@ class E2EEManager {
   /// if null, use local participant.
   Future<void> setKeyIndex(int keyIndex, {String? participantIdentity}) async {
     participantIdentity ??= _room?.localParticipant?.identity;
-    for (var item in _frameCryptors.entries) {
+    for (var item in _frameCryptors.entries.toList()) {
       if (item.key.keys.first == participantIdentity) {
         await item.value.setKeyIndex(keyIndex);
       }
@@ -202,7 +202,7 @@ class E2EEManager {
   /// @return the key index and -1 if not found
   Future<int> getKeyIndex(String? participantIdentity) async {
     participantIdentity ??= _room?.localParticipant?.identity;
-    for (var item in _frameCryptors.entries) {
+    for (var item in _frameCryptors.entries.toList()) {
       if (item.key.keys.first == participantIdentity) {
         return await item.value.keyIndex;
       }

lib/src/managers/event.dart

@@ -133,7 +133,9 @@ abstract class EventsListenable<T> extends Disposable {
     if (_listeners.isNotEmpty) {
       // Stop listening to all events
       logger.finer('${objectId} cancelling ${_listeners.length} listeners(s)');
-      for (final listener in _listeners) {
+      final listenersCopy = List.of(_listeners);
+      _listeners.clear();
+      for (final listener in listenersCopy) {
         await listener.cancel();
       }
     }

lib/src/track/web/_audio_html.dart

@@ -52,7 +52,7 @@ Future<dynamic> startAudio(String id, rtc.MediaStreamTrack track) async {
 }
 
 Future<bool> startAllAudioElement() async {
-  for (final el in _audioElements.values) {
+  for (final el in _audioElements.values.toList()) {
     if (el.instanceOfString('HTMLAudioElement')) {
       final audio = el as web.HTMLAudioElement;
       await audio.play().toDart;