This seems to be unintended side-effect of an unrelated improvement. In v6, the I/O properly respect the fact that a class has a custom Streamer (assuming because the default I/O is not sufficient for that class) and ensure that such custom Streamer are called whenever those objects are stored. In practice this means that some class that were stored in split mode, thus skipping the call to the Streamer function are no longer split.
In the case of TTime
, the dictionary generated is requesting the ‘very’ old I/O for the class TTime
. In practice this means that not only it can no longer be split but it also does not record the description of the TTime
classes. As is uproot
would need to add explicitly support for this class to be able to read.
Now, it also turns out that there does not seems to be any good reason to use the very old I/O (and thus a sort of custom Streamer) for this Class. So this is a bug that we need to resolve.