fix: BREAKING! Cache members for encrypted rooms in database

This fixes a huge performance
leak as for every encrypted room
the whole member list is loaded
every time you start the client.
This also changes the default value of `cache` in
this method to if the room is encrypted or not.
For encrypted rooms we always want a complete
member list locally.

lib/fake_matrix_api.dart

@@ -1816,19 +1816,62 @@ class FakeMatrixApi extends BaseClient {
       '/client/v3/rooms/!localpart%3Aserver.abc/members': (var req) => {
             'chunk': [
               {
+                'type': 'm.room.member',
+                'content': {'membership': 'join', 'displayname': 'YOU'},
+                'sender': '@test:fakeServer.notExisting',
+                'state_key': '@test:fakeServer.notExisting',
+                'room_id': '!localpart%3Aserver.abc',
+                'event_id': '§143273582443PhrSn2:example.org',
+                'origin_server_ts': 1432735824653,
+                'unsigned': {'age': 1234},
+              },
+              {
+                'type': 'm.room.member',
+                'content': {
+                  'membership': 'join',
+                  'displayname': 'Alice Margatroid',
+                },
+                'sender': '@alice:matrix.org',
+                'state_key': '@alice:matrix.org',
+                'room_id': '!localpart%3Aserver.abc',
+                'event_id': '§143273582443PhrSn3:example.org',
+                'origin_server_ts': 1432735824653,
+                'unsigned': {'age': 1234},
+              },
+              {
+                'type': 'm.room.member',
+                'content': {'membership': 'invite', 'displayname': 'Bob'},
+                'sender': '@bob:example.com',
+                'state_key': '@bob:example.com',
+                'room_id': '!localpart%3Aserver.abc',
+                'event_id': '§143273582443PhrSn4:example.org',
+                'origin_server_ts': 1432735824653,
+                'unsigned': {'age': 1234},
+              },
+              {
+                'type': 'm.room.member',
+                'content': {'membership': 'invite', 'displayname': 'Charley'},
+                'sender': '@charley:example.org',
+                'state_key': '@charley:example.org',
+                'room_id': '!localpart%3Aserver.abc',
+                'event_id': '§143273582443PhrSn5:example.org',
+                'origin_server_ts': 1432735824653,
+                'unsigned': {'age': 1234},
+              },
+              {
+                'type': 'm.room.member',
                 'content': {
                   'membership': 'join',
                   'avatar_url': 'mxc://example.org/SEsfnsuifSDFSSEF',
                   'displayname': 'Alice Margatroid',
                 },
-                'type': 'm.room.member',
-                'event_id': '§143273582443PhrSn:example.org',
-                'room_id': '!636q39766251:example.com',
                 'sender': '@example:example.org',
+                'state_key': '@alice:example.org',
+                'room_id': '!localpart%3Aserver.abc',
+                'event_id': '§143273582443PhrSn6:example.org',
                 'origin_server_ts': 1432735824653,
                 'unsigned': {'age': 1234},
-                'state_key': '@alice:example.org',
+              },
-              }
             ],
           },
       '/client/v3/pushrules/global/content/nocake': (var req) => {

lib/src/room.dart

@@ -1607,6 +1607,8 @@ class Room {
   /// [[Membership.join, Membership.invite, Membership.knock]]
   /// Set [cache] to `false` if you do not want to cache the users in memory
   /// for this session which is highly recommended for large public rooms.
+  /// By default users are only cached in encrypted rooms as encrypted rooms
+  /// need a full member list.
   Future<List<User>> requestParticipants([
     List<Membership> membershipFilter = const [
       Membership.join,
@@ -1614,7 +1616,7 @@ class Room {
       Membership.knock,
     ],
     bool suppressWarning = false,
-    bool cache = true,
+    bool? cache,
   ]) async {
     if (!participantListComplete || partial) {
       // we aren't fully loaded, maybe the users are in the database
@@ -1633,6 +1635,8 @@ class Room {
       return getParticipants(membershipFilter);
     }
 
+    cache ??= encrypted;
+
     final memberCount = summary.mJoinedMemberCount;
     if (!suppressWarning && cache && memberCount != null && memberCount > 100) {
       Logs().w('''
@@ -1651,6 +1655,14 @@ class Room {
     if (cache) {
       for (final user in users) {
         setState(user); // at *least* cache this in-memory
+        await client.database?.storeEventUpdate(
+          EventUpdate(
+            roomID: id,
+            type: EventUpdateType.state,
+            content: user.toJson(),
+          ),
+          client,
+        );
       }
     }
 

test/room_test.dart

@@ -657,14 +657,17 @@ void main() {
     });
 
     test('requestParticipants', () async {
-      final participants = await room.requestParticipants();
+      final oldParticipants = room.getParticipants();
-      expect(participants.length, 4);
+      expect(oldParticipants.length, 4);
-      final user = participants.singleWhere((u) => u.id == '@alice:matrix.org');
+      room.summary.mJoinedMemberCount = 5;
-      expect(user.id, '@alice:matrix.org');
+      final fetchedParticipants = await room.requestParticipants(
-      expect(user.displayName, 'Alice Margatroid');
+        const [Membership.join, Membership.invite, Membership.knock],
-      expect(user.membership, Membership.join);
+        true,
-      //expect(user.avatarUrl.toString(), 'mxc://example.org/SEsfnsuifSDFSSEF');
+        true,
-      expect(user.room.id, '!localpart:server.abc');
+      );
+      final newParticipants = room.getParticipants();
+      expect(oldParticipants.length < newParticipants.length, true);
+      expect(fetchedParticipants.length, newParticipants.length);
     });
 
     test('calcEncryptionHealthState', () async {
@@ -823,7 +826,7 @@ void main() {
 
     test('getParticipants', () async {
       var userList = room.getParticipants();
-      expect(userList.length, 4);
+      expect(userList.length, 5);
       // add new user
       room.setState(
         Event(
@@ -837,8 +840,8 @@ void main() {
         ),
       );
       userList = room.getParticipants();
-      expect(userList.length, 5);
+      expect(userList.length, 6);
-      expect(userList[4].displayName, 'alice');
+      expect(userList[5].displayName, 'alice');
     });
 
     test('addToDirectChat', () async {
@@ -1660,7 +1663,7 @@ void main() {
       matrixToLink = await room.matrixToInviteLink();
       expect(
         matrixToLink.toString(),
-        'https://matrix.to/#/!localpart%3Aserver.abc?via=fakeServer.notExisting&via=matrix.org&via=test.abc',
+        'https://matrix.to/#/!localpart%3Aserver.abc?via=fakeServer.notExisting&via=matrix.org&via=example.org',
       );
     });