Details
I was triaging tasks on an instance of Phorge, and I got to a duplicate task (https://issue-tracker.miraheze.org/T12276). I then closed it as a duplicate of an existing task, but not before someone else closed it as a duplicate, causing the task to be closed twice:
I would've expected at least a box saying that the action has already been done (like when two people close a task at the same time). Is this intentional, or a bug?
Answer Summary
This is not intentional (see the two answers posted). A bug report has been filed: T15875
Answers
This might be a race condition. (Related code in https://we.phorge.it/source/phorge/browse/master/src/applications/maniphest/relationship/ManiphestTaskCloseAsDuplicateRelationship.php$56-58 allows to only select one single task to merge into, thus the "Select" button in the corresponding UI dialog should be disabled.)
Your video is awesome. Very probably not intentional :)
To get eternal glory, feel free to escalate this question as a Task under Bug Reports 🌈 (you can just close this question as Obsolete and copy-paste the content in the Task at the moment)
...and welcome in the family of Trusted Contributors that allows to do so! ✨
I would say: patch welcome!