Add self to the group when a MUA reply is received

[anaskaejdar]

• Operating System (Linux/Mac/Windows/iOS/Android): Android
• Delta Chat Version: 1.38.4

Expected behavior:

There are at least a couple ways it could be handled:

• Deltachat would ignore a user added via a traditional MUA if that user was recently removed from the group. Deltachat would not put this user back into the member list. (I believe this is by far the more preferable behavior.)
  • Maybe DC considers whether the message is a reply to a previous message that was sent before the user was removed from the group.
• The removed user's deltachat client would recognize that he/she has been added back into the group by the traditional MUA user.

Actual behavior:

It creates a major discrepancy in room state between the removed user and all the other users. The deltachat user that was removed continues to receive messages, but cannot himself send anything to the group. Why? His deltachat still only thinks he has been removed from the group. From his own perspective, he does not appear in the group's member list, and thus the text box et al are hidden away.

The strange part is that the other deltachat users in the same group will perceive that he is a member once again. He will appear in the member list just as before. For this reason, he will continue to receive messages from the group, though he cannot respond to them.

Steps to reproduce the problem:

1. Have a bunch of email addresses to test with
2. Make a group of three or four (or more) addresses.
3. Send a message to the group
4. Remove one of the members
5. From a different address, and using a traditional MUA like K9Mail, send a reply-all in response to the earlier message (step 3)
6. (notice: The removed user is almost certainly there in the To: field)
7. In deltachat, perceive that the removed user is once again included in the member list, because of his inclusion in the traditional MUA message (step 5).
8. In deltachat, send a message to the group
9. (notice: The removed user received the message.)
10. Try to send something to the group in deltachat, from the user that was removed in step 4.
11. (notice: You cannot send anything to the group, as the text box is hidden away from you.)

• Screenshots:
• Logs:

[gerryfrancis]

@anaskaejdar Thank you for your very detailed report. I think the origin of the problem is the fact that messages about the removal of group members are sent to the affected members as well. Thus, messages sent from a MUA as reply to all afterwards are not helpful and will re-add already removed members to groups. As we cannot prohibit a MUA group user to send messages to already removed group members, the question at hand would be how to deal with such situations.

I could think of sending the removal message (which is the last a removed member is expected to receive) as bcc to the member who is about to be removed from the group. Then, when a MUA group user was about to reply to all afterwards, the removed member would not be applied to the list of recipients automatically anymore.

[link2xt]

This was likely introduced in #4185

The user being added back to the group as a result of a reply to an earlier message is expected, so as I understand the bug is that the removed user does not recognize that it is re-added. Then the solution is

The removed user's deltachat client would recognize that he/she has been added back into the group by the traditional MUA user.

[anaskaejdar]

Sounds good to me. The BCC idea is great, also.

Additionally, maybe if DC thinks you've been removed from a group, rather than merely hiding the input fields, it could replace them with a little message explaining why they're gone, and a button to _un_hide them if the user wants.

[iequidoo]

Fixed by #4638