So yeah I gave reqnroll/Reqnroll/issues/872 a wack and I managed to populate TestAttribute with File and Line as you proposed but it wont work.
I tried to pinpoint exactly where there error is and I found that in TUnit it looks like TestAttribute's values is never selected if the previous block is selected first in these two methods:

I managed to get it behave correctly, at least from a gen perspective, when switching the blocks and when watching the generated files.
I couldn't make the project to work fully as so I could not run all unit tests and some fails regardless of there are changes or not.