Unassigned user removal

Steps to reproduce

• Import issues that were originally set to Unassigned (The option of Allow Unassigned Issues is set to ON)
• Perform a bulk edit of issues
• After the bulk edit process is completed, it created a new user called Unassigned

Expected behavior

• The issues should be assigned to the system Unassigned rather than the Unassigned user that was created during the import of issues

Actual behavior

• The system assigned back the issues to the Unassigned user that was created and even after the original issues were updated to have NULL assignee, it clashes with the system Unassigned, which eventually causes the removal of the created Unassigned user to be halted.
• The system did not recognize all the issues had a NULL assignee rather than doing what appeared to be a string match on Unassigned

The user was trying to perform a bulk edit of 41 issues which were intended to be left as Unassigned. When the process was completed, it somehow created an Unassigned user. When the user tries to delete the user, he was told that it is not possible because there were ~6000 issues assigned to it.

Diving into the database to check on what could be the reason, the user saw that the jiraissue table has issues with ASSIGNEE="unassigned", whereby the Unassigned issues have the ASSIGNEE=NULL.

After updating the 41 issues to have the assignee of NULL, the user was still unable to delete the Unassigned user from the Users page as it says that there are still ~6000 issues assigned to it.

The workaround that we managed to figure out was the following:

1. Create User A and User B
2. Turn off email notifications
3. Bulk assign all open unassigned tickets to User A
4. Bulk open all closed unassigned tickets and assign to User B
5. Delete the Unassigned user
6. Change all the tickets assigned to User A to blank value
7. Change all the tickets assigned to User B to blank value and close them
8. Turn on email notifications again

It worked and the following was the customer's feedback on the issue that we were facing:

I always understood why the "unassigned" user was created. I think the main problem is how the system differentiates between this and the system unassigned function or NULL assignee.

Most notably, I could see in the jiraissue table the imported issues all had an assignee of "unassigned", which was expected as that user was created during the import. However, I was able to delete this value through the Jira UI, which should then have assigned the issues to the system unassigned function. I could see these changes were reflected in the database, as subsequently to the change each issue had an assignee of NULL (ie system unassigned rather than user "unassigned").

What I found odd was that that data didn't seem to be honoured when trying to delete the user - somewhere else in the system it was doing a comparison which I don't believe was correct - it should've recognised all the issues had a NULL assignee rather than doing what appeared to be a string match on "Unassigned".

Perhaps there might be some explanation to this?