`.first()` and `.prefix(1)` different behaviors?

Using Swift
1

Hello!

I noticed a behavioral difference between first() and prefix(1) and I'm not sure why this happens - I might just not understand something here.

I'm basically doing a flatMapLatest with a side-effect (don't judge, i'm experimenting)

import Combine

let sourceSubject = CurrentValueSubject<Int, Never>(1)
let targetPublisher = Just("Hello").delay(for: .seconds(3), scheduler: RunLoop.main)

let subscription = sourceSubject
    .removeDuplicates()
    .prefix(1) //    .first()
    .handleEvents(
        receiveSubscription: { print("source receive subscription \($0)") },
        receiveOutput: { print("source receive output \($0)") },
        receiveCompletion: { print("source receive completion \($0)") },
        receiveCancel: { print("source receive cancel") },
        receiveRequest: { print("source receive request \($0)") }
    )
    .map { _ in
        targetPublisher
    }
   // Side effect, without it everything behaves the same
    .handleEvents(receiveOutput: { _ in
        sourceSubject.value = 2
    })
    .switchToLatest()
    .handleEvents(
        receiveSubscription: { print("target receive subscription \($0)") },
        receiveOutput: { print("target receive output \($0)") },
        receiveCompletion: { print("target receive completion \($0)") },
        receiveCancel: { print("target receive cancel") },
        receiveRequest: { print("target receive request \($0)") }
    )
    .sink {
        print("Sink value: \($0)")
    }

DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(5)) {
    subscription.cancel()
}

While with first() everything behaves as I expected:

target receive subscription SwitchToLatest
target receive request unlimited
source receive subscription First
source receive request unlimited
source receive output 1
Send new subject value
source receive completion finished
target receive output Hello
Sink value: Hello
target receive completion finished

with prefix(1), the resulting publisher completes immediately:

target receive subscription SwitchToLatest
target receive request unlimited
source receive subscription Output
source receive request unlimited
source receive output 1
Send new subject value
source receive completion finished
target receive completion finished

Is this expected? If so, does anyone know the root reason?

Thanks a lot :pray: