Last remaining message in thread disappears when others are deleted

[bilogic]

vid.mp4

Describe the bug
When viewing a thread, if I were to delete earlier messages, the sole remaining message disappears as well. It only shows up again after back to message list.

This is scary because a new user can interpret that as a bug, i.e. all my messages were deleted when I wanted to keep one and delete the rest.

To Reproduce
Steps to reproduce the behavior:
See video

Expected behavior
The message that was not deleted should remain visible.

Screenshots
See video

Please complete the following information:

• Browser: Chrome Version 128.0.6613.138 (Official Build) (64-bit)
• IMAP daemon: dovecot
• PHP version: 8.2
• SnappyMail Version: djmaze/snappymail latest 7b93403c8a35
• Mode: docker

Sorry about the snappymail version, I'm not sure where to find it that is the docker hash.

Debug/logging information
Read here how to log

Additional context
none

[the-djmaze]

Correct, because then there is not thread anymore.

[bilogic]

If there is no more thread, can make it auto back to message list? Empty message list is scary.

[the-djmaze]

Not really, but we could think of a different solution.
Maybe a different message?

[bilogic]

Ok, let's review:

1. I deleted 5 message but 6(!!) disappeared
2. The user needs to be re-assured that the 6th was not deleted
3. The best assurance is to show it to the user

I tested on gmail, it stays in thread view even though there is only 1 message left.
Why must a thread have 2 or more messages?

[bilogic]

Is thread an IMAP feature defined as 2 or more messages?
If thread is defined by SnappyMail, why not redefine thread as 1 or more messages, but threads with only 1 message cannot enter into Message List?