A handy Combine operator if you are only interested in a publisher completing: `MapVoid`

MapVoid.swift

import Combine

extension Publisher {
    func mapVoid() -> MapVoid<Self> {
        MapVoid(upstream: self)
    }
}

struct MapVoid<P: Publisher>: Publisher {
    typealias Output = Void
    typealias Failure = Never

    let upstream: Publishers.ReplaceError<Publishers.Map<P, Void>>
    init(upstream: P) {
        self.upstream = upstream
            .map { _ in () } // map all values to Void
            .replaceError(with: ()) // replace all errors with Void
    }

    public func receive<S>(subscriber: S) where S : Subscriber, S.Input == Void, S.Failure == Never {
        upstream.receive(subscriber: subscriber)
    }
}

Turns a publisher into: Publisher<Void, Never>. Useful if you're combining multiple publishers and only care to know when they're complete. Especially if you're flat mapping multiple publishers with different output and failure types.