fix: don't convert archived rooms to joined rooms by accident

When decrypting the last event for archived rooms when a room key is
received, we used to send a synthetic SyncUpdate. This however put the
archived room into the join section, which converted the room to a
joined room. We need to respect what section the room was in when
sending synthetic SyncUpdates.

fixes https://github.com/famedly/matrix-dart-sdk/issues/1916

lib/encryption/key_manager.dart

@@ -164,6 +164,7 @@ class KeyManager {
     if (!client.isLogged() || client.encryption == null) {
       return;
     }
+
     final storeFuture = client.database
         ?.storeInboundGroupSession(
       roomId,
@@ -200,8 +201,19 @@ class KeyManager {
           await client.database?.transaction(() async {
             await client.handleSync(
               SyncUpdate(
-                  nextBatch: '',
+                nextBatch: '',
-                  rooms: RoomsUpdate(join: {room.id: JoinedRoomUpdate()})),
+                rooms: switch (room.membership) {
+                  Membership.join =>
+                    RoomsUpdate(join: {room.id: JoinedRoomUpdate()}),
+                  Membership.ban ||
+                  Membership.leave =>
+                    RoomsUpdate(leave: {room.id: LeftRoomUpdate()}),
+                  Membership.invite =>
+                    RoomsUpdate(invite: {room.id: InvitedRoomUpdate()}),
+                  Membership.knock =>
+                    RoomsUpdate(knock: {room.id: KnockRoomUpdate()}),
+                },
+              ),
             );
           });
         }

lib/matrix_api_lite/model/sync_update.dart

@@ -114,11 +114,13 @@ class RoomsUpdate {
   Map<String, JoinedRoomUpdate>? join;
   Map<String, InvitedRoomUpdate>? invite;
   Map<String, LeftRoomUpdate>? leave;
+  Map<String, KnockRoomUpdate>? knock;
 
   RoomsUpdate({
     this.join,
     this.invite,
     this.leave,
+    this.knock,
   });
 
   RoomsUpdate.fromJson(Map<String, Object?> json) {
@@ -128,6 +130,8 @@ class RoomsUpdate {
         MapEntry(k, InvitedRoomUpdate.fromJson(v as Map<String, Object?>)));
     leave = json.tryGetMap<String, Object?>('leave')?.catchMap((k, v) =>
         MapEntry(k, LeftRoomUpdate.fromJson(v as Map<String, Object?>)));
+    knock = json.tryGetMap<String, Object?>('knock')?.catchMap((k, v) =>
+        MapEntry(k, KnockRoomUpdate.fromJson(v as Map<String, Object?>)));
   }
 
   Map<String, Object?> toJson() {
@@ -141,6 +145,9 @@ class RoomsUpdate {
     if (leave != null) {
       data['leave'] = leave!.map((k, v) => MapEntry(k, v.toJson()));
     }
+    if (knock != null) {
+      data['knock'] = knock!.map((k, v) => MapEntry(k, v.toJson()));
+    }
     return data;
   }
 }
@@ -234,6 +241,28 @@ class InvitedRoomUpdate extends SyncRoomUpdate {
   }
 }
 
+class KnockRoomUpdate extends SyncRoomUpdate {
+  List<StrippedStateEvent>? knockState;
+
+  KnockRoomUpdate({this.knockState});
+
+  KnockRoomUpdate.fromJson(Map<String, Object?> json)
+      : knockState = json
+            .tryGetMap<String, List<Object?>>('knock_state')?['events']
+            ?.map((i) => StrippedStateEvent.fromJson(i as Map<String, Object?>))
+            .toList();
+
+  Map<String, Object?> toJson() {
+    final data = <String, Object?>{};
+    if (knockState != null) {
+      data['knock_state'] = {
+        'events': knockState!.map((i) => i.toJson()).toList(),
+      };
+    }
+    return data;
+  }
+}
+
 class LeftRoomUpdate extends SyncRoomUpdate {
   List<MatrixEvent>? state;
   TimelineUpdate? timeline;

test/room_archived_test.dart

@@ -23,7 +23,7 @@ import 'package:test/test.dart';
 import 'package:matrix/matrix.dart';
 import 'fake_client.dart';
 
-void main() {
+void main() async {
   group('Timeline', () {
     Logs().level = Level.error;
 
@@ -115,6 +115,66 @@ void main() {
       expect(client.getArchiveRoomFromCache('!5345234235:example.com'), null);
     });
 
+    test("assert that key updates don't change membership", () async {
+      const roomid = '!5345234235:example.com';
+
+      // prep work to be able to set a last event that would trigger the (fixed) bug
+      await client.loadArchiveWithTimeline();
+      expect(client.getArchiveRoomFromCache(roomid) != null, true);
+      expect(client.getRoomById(roomid)?.membership, Membership.leave);
+
+      final outboundSession = await client.encryption?.keyManager
+          .createOutboundGroupSession(roomid);
+      final inboundSession = client.encryption!.keyManager
+          .getInboundGroupSession(
+              roomid, outboundSession!.outboundGroupSession!.session_id())!;
+
+      // ensure encryption is "enabled"
+      client.getRoomById(roomid)?.setState(StrippedStateEvent(
+            type: EventTypes.Encryption,
+            content: {'algorithm': AlgorithmTypes.megolmV1AesSha2},
+            senderId: client.userID!,
+            stateKey: '',
+          ));
+      final encryptedEvent = await client.encryption!
+          .encryptGroupMessagePayload(
+              roomid, {'msgtype': 'm.room.text', 'body': 'empty'});
+
+      // reset client
+      await client.dispose().onError((e, s) {});
+      client = await getClient(
+        sendTimelineEventTimeout: const Duration(seconds: 5),
+      );
+
+      await client.abortSync();
+      insertList.clear();
+
+      // now do our tests
+      await client.loadArchiveWithTimeline();
+      expect(client.getArchiveRoomFromCache(roomid) != null, true);
+      expect(client.getRoomById(roomid)?.membership, Membership.leave);
+
+      // set the last event
+      final room = client.getRoomById(roomid)!;
+      room.lastEvent = Event(
+          type: EventTypes.Encrypted,
+          content: encryptedEvent,
+          senderId: client.userID!,
+          eventId: '\$archivedencr',
+          room: room,
+          originServerTs: DateTime.now());
+
+      // import the inbound session
+      await client.encryption!.keyManager.setInboundGroupSession(
+          roomid,
+          inboundSession.sessionId,
+          inboundSession.senderKey,
+          inboundSession.content);
+
+      expect(client.getArchiveRoomFromCache(roomid) != null, true);
+      expect(client.getRoomById(roomid)?.membership, Membership.leave);
+    }, tags: 'olm');
+
     test('clear archive', () async {
       await client.loadArchiveWithTimeline();
       client.clearArchivesFromCache();