The main loop from the AsyncSequencePublisher - See full file here: https://github.com/josephlord/AsyncSequnceExtensions/blob/main/Sources/AsyncSequenceExtensions/AsyncSequencePublisher.swift

AsyncSequencePublisherMainLoop.swift

/// Kicks off the main loop over the async sequence. Does the main work within the for loop over the async seqence
/// - Parameters:
///   - seq: The AsyncSequence that is the source
///   - sub: The Subscriber to this Subscription
private func mainLoop(seq: AsyncSequenceType, sub: S) {
    // taskHandle is kept for cancelation
    taskHandle = Task {
        do {
            try await withTaskCancellationHandler {
                Task.detached {
                    let cont = await self.innerActor.getContinuationToFireOnCancelation()
                    cont?.resume()
                }
            } operation: {
                for try await element in seq {
                    // Check for demand before providing the first item
                    await self.innerActor.waitUntilReadyForMore()
                    guard !Task.isCancelled else { return } // Exit if cancelled
                    let newDemand = sub.receive(element) // Pass on the item
                    let cont = await self.innerActor.add(demand: newDemand)
                    assert(cont == nil,
                           "If we are't waiting on the demand the continuation will always be nil")
                    // cont should always be nil as it will only be set when this loop is
                    // waiting on demand
                    cont?.resume()

                }
                // Finished the AsyncSequence so finish the subcription
                sub.receive(completion: .finished)
                return
            }
        } catch {
            // Cancel means the subscriber shouldn't get more, even errors so exit
            if error is CancellationError { return }
            sub.receive(completion: .failure(error))
        }
    }
}