What is the expected thread on which a .collect operation in Swift's Combine will emit?
Specifically I am seeing this code crash in the second precondition, but not the first:
return Publishers.MergeMany(publishers)
.handleEvents(receiveOutput: { _ in
precondition(Thread.isMainThread) // <- This is fine
})
.collect()
.handleEvents(receiveOutput: { _ in
precondition(Thread.isMainThread) // <- Crash is here
})
It is as if the .collect operation is picking a different thread to use, even though the final publisher in the MergeMany must have emitted on the main thread. I have deduced this behavior via crash logs uploaded from Firebase. Can anyone explain this observed behavior?
