IssueTracker

As a general note, what you're checking makes little sense - onAttachFragment is called as fragments move through their lifecycle methods (specifically, right after onAttach() is called on the fragment) and is therefore likely to be called while FragmentTransactions are being processed - if you have multiple commit()s in flight, the state you get back in onAttachFragment will certainly not be the final state the FragmentManager will be when all of the FragmentTransactions are executed, making this a bit of a meaningless check.

That being said, this is caused by the mechanism used to kick off transitions when reordering is not allowed, which is being reworked in b/147749580 which should remove this problem entirely (ensuring that the fragment is added to the FragmentManager before calling any lifecycle methods on it, attach included).

As a workaround, you can use setReorderingAllowed(true) on your transaction, which will allow your example project to work correctly.