Composed implementation of `Publisher.withLatestFrom`’s that handled finished events.

with_latest_from_handling_finished_events.swift

extension Publisher {
	func withLatestFrom<Other: Publisher>(
		_ other: Other
	) -> AnyPublisher<Other.Output, Other.Failure>
	where Failure == Other.Failure {
		let upstream = share()

		return other
			.map { second in upstream.map { _ in second  } }
			.switchToLatest()
			.zip(upstream) // `zip`ping and discarding `\.1` allows for
			// upstream completions to be projected down immediately.
			.map(\.0)
			.eraseToAnyPublisher()
	}
}

let first = PassthroughSubject<Int, Never>()
let second = PassthroughSubject<String, Never>()
var cancellables = Set<AnyCancellable>()

first
	.withLatestFrom(second)
	.sink(receiveCompletion: { print($0) }, receiveValue: { print($0) })
	.store(in: &cancellables)

first.send(completion: .finished)

// Outputs:
//
// ```
// finished
// ```