The test requires subtle conditions to trigger:
- initialize a timeline from a room-list-service's room
- start a backpagination with that timeline (so the room event cache's
paginator is busy)
- try to initialize another timeline with the same room-list-service's
room (e.g. because the first room has been closed, and the app using it
doesn't have a room cache)
This would fail, because initializing a timeline calls
`EventCache::add_initial_events()` all the time, which tries to reset
the paginator's state, which assumes the paginator's not paginating at
this point. In a soon future, we'll get rid of the
`add_initial_events()` function because the event cache will handle its
own persistent storage; in the meantime, a correct fix is to skip
`add_initial_events()` if there was already something in the linked
chunk. After all, we're likely to fill the initial events with the same
events all the time, or a subset of more recent events. By doing that,
we're likely keeping *more* events in the linked chunk, instead.
Thanks to @stefanceriu for reporting the issue and confirming the fix
works!
Benjamin Bouvier
bf6fa4cd55