Swift: Handling actor reentrancy correctly

ActorReentrancy.swift

// Code from: https://alexdremov.me/swift-actors-common-problems-and-tips/

import Foundation

actor ActivitiesStorage {
    var cache = [UUID: Task<Data?, Never>]()
    
    func retrieveHeavyData(for id: UUID) async -> Data? {
        if let task = cache[id] {
            return await task.value
        }
        
        // ...
        
        let task = Task {
            await requestDataFromDatabase(for: id)
        }
        
        // Notice that it is set before `await`
        // So, the following calls will have this task available
        cache[id] = task
        return await task.value // suspension
    }
    
    private func requestDataFromDatabase(for id: UUID) async -> Data? {
        print("Performing heavy data loading!")
        try! await Task.sleep(for: .seconds(1))
        // ...
        return nil
    }
    
}

let id = UUID()
let storage = ActivitiesStorage()

Task {
    let data = await storage.retrieveHeavyData(for: id)
}

Task {
    let data = await storage.retrieveHeavyData(for: id)
}