Publisher+makeHot.swift

import Combine

extension Publisher {
  func makeHot() -> AnyPublisher<Output, Failure> {
    let subject = PassthroughSubject<Void, Never>()
    let publisher = map(Result.success)
      .catch { Just(.failure($0)) }
      .prefix(untilOutputFrom: subject)
      .makeConnectable()
    let connection = publisher.connect()
    return publisher.flatMap(\.publisher)
      .handleEvents(receiveCompletion: { _ in
        subject.send(())
        connection.cancel()
      })
      .eraseToAnyPublisher()
  }
}