Member count should never allowed to go down without members removed showing

[ell1e]

The member count should never allowed to go down without members removed being shown as some sort of message that can be interacted with. The member count for a group I went in went down from around 110 to around 70, but there are no member removal messages for the members that left.

This group seems to have been previously split with slightly inconsistent state, which in itself is fine, but if my client recognizes and accepts any removals then it must show me the removals so I can revert them. Anything else seems like a serious problem when handling groups as a user.

• Operating System (Linux/Mac/Windows/iOS/Android): Linux
• Core Version: 2.11.0
• Client Version: 2.11.1 (git: flathub)

Expected behavior

Any removal leads to a message that has the necessary info to reverse it (which is usually the email showing up when I click on the message).

Actual behavior

Member count silently went down by about 40. There are no removal messages in the log, nothing indicating a change.

Steps to reproduce the problem

1. Probably complicated to get a group into such a disjoint state to start with.

Screenshots

Logs

[ell1e]

What seems to have happened before is that I got a removal message by somebody in the group, and my client showed "Member Me removed by user", but since the member removing me wasn't in the group any longer I assumed it wasn't effective. I could still write and talk to some other people so that seemed like a safe guess.

But then at some point I was added back despite from my end never having been removed, leading to "Member myemailadress added by otheruser" and I think that is when the member list just silently changed. I don't think being added back when my client thought it wasn't ever removed should lead to a silent(!!) member list change, my client should either 1. reject the change of member list, or 2. show the changes as removed and added messages.

[gerryfrancis]

@ell1e Maybe a stupid question of mine, but could it be true that someone cleaned up the group and caused a huge amount of emails that were sent at once and were recognized as SPAM by your mail server? Also, I suppose that member lists of IDs are updated by gossip, too, which might be an explanation why you have not received any info message for adding/removing members, at least not for each of them. Just guessing...

[ell1e]

Even if it were updated via gossip it should really show removed and added messages. That was basically why I filed this ticket. The method of update shouldn't matter.

[iequidoo]

1. reject the change of member list, or 2. show the changes as removed and added messages.

The fix is "2", we can't reject all member changes because there may be "fresh" member changes about which we mayn't know if we missed some messages. But i also decided to limit compatibility with old Delta Chat clients who don't provide timestamps for member changes, i.e. reject member changes from them, because we can't know if such changes are fresh.