Invites are collapsed incorrectly

[ara4n]

I created a room and invited two people to it. The timeline says:

which is wrong: there are 2 memberships, and the avatars should show the invited user not the invitee. “2 users invited” would be correct.

[Johennes]

I have a partial fix that addresses the wrong number in matrix-org/matrix-ios-kit#789. The issue only occurs when the collapsed events are processed in different batches (which, for instance, happens when you invite multiple people one by one).

I've only very briefly looked into the avatar issue. The app is currently using the sender's avatar. For invites, it looks like the only place in the event where we could get the invitee's username from is state_key.

"{
  "sender": "@alice:matrix.org",
  "content": {
    "displayname": "bob",
    "membership":"invite"
  },
  "origin_server_ts": 1616488993287,
  "state_key": "@bob:matrix.org", <=====
  "room_id": "...",
  "event_id": "...",
  "type": "m.room.member",
  "unsigned": {
    "age": 1204610,
    "prev_sender": "@alice:matrix.org",
    "prev_content": ...,
    "replaces_state": "..."
  }
}

[Johennes]

I have another incremental fix that addresses the wrong avatars in matrix-org/matrix-ios-kit#793 and #4148.

The logic around combining membership changes and building the summary string is still not as advanced as on Element web but bring that on par is an endeavor of its own.