Bug 308952

This bug seems related to 308378 - https://bugs.kde.org/show_bug.cgi?id=308378 - but I do not get any messages about the folder not existing. Therefore I decided to post it as a new report.
I was also unsure whether it should be reported as a Akonadi or KMail2 problem, feel free to reassign :-)

In a (local) folder I had three messages.
I renamed the folder (from Vivaldi to Plasma Active, not that it should matter) and moved three more messages to the folder.
In the message list, all messages were displayed, but only the new messages would be displayed when selected.

I suspected the problem was related to the renaming of the folder.
Now, in slight desperation, I tried several tricks, so my memory is perhaps not complete. As a software developer I should be sensible enough to write down the steps once I suspected it was a bug - but unfortunately I was not.

Now, as I am writing this, I have two folders. One named Plasma Active and one named Vivaldi. I believe the Vivaldi is the original folder re-named again in the hope that the messages would magically reappear, and the Plasma Active is a new folder I created (sibling of Vivaldi). However, memory may serve me wrong, and I may also have renamed the folder more than twice.

Anyway, the end result was that none of the folders displayed any messages!
However, in disk folder "~/.local/share/.local-mail.directory/.KDE.directory/Vivaldi/new" the original three messages are present - so the mail has not been lost.

The three new messages I had moved to the folder after renaming it mysteriously disappeared, but were found again in the inbox and sent mail folders - who said computers are not intelligent!

I tried to move one of those messages to the Plasma Active folder. The message now appears in both the Plasma Active folder and the Vivaldi folder in KMail, but on disk it is found in the "~/.local/share/.local-mail.directory/.KDE.directory/Plasma Active/new" folder.

I closed KMail (Kontact) and re-opened it. That did not solve or create any problems, i.e. the Plasma Active and Vivaldi folders still show the message I moved to the Plasma Active folder - and the folders on disk still have the correct messages as described above.

Reproducible: Always

Steps to Reproduce:
1. Create a local folder and move a message into it.
2. Rename the folder and move another message into it.
3. Click on the message you first moved into the folder to display it.
Actual Results:  
Message is not displayed in message view area.

Expected Results:  
Message is displayed in message view area.

Although the data are not actually lost they appear to be lost, and only people who know where to look will find the messages. If KMail had been able to restore correct display after a restart the problem would not be as severe as it now (in my opinion) is.