Offering: Sendable conformance

The type is now immutable, so the compiler ensures it's thread-safe.

For [CSDK-379].
Extracted from #1795 to make it easier to review this in isolation.

Sources/Purchasing/Offering.swift

@@ -26,7 +26,7 @@ import Foundation
  * - ``Offerings``
  * - ``Package``
  */
-@objc(RCOffering) public class Offering: NSObject {
+@objc(RCOffering) public final class Offering: NSObject {
 
     /**
      Unique identifier defined in RevenueCat dashboard.
@@ -46,37 +46,37 @@ import Foundation
     /**
      Lifetime ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var lifetime: Package?
+    @objc public let lifetime: Package?
 
     /**
      Annual ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var annual: Package?
+    @objc public let annual: Package?
 
     /**
      Six month ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var sixMonth: Package?
+    @objc public let sixMonth: Package?
 
     /**
      Three month ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var threeMonth: Package?
+    @objc public let threeMonth: Package?
 
     /**
      Two month ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var twoMonth: Package?
+    @objc public let twoMonth: Package?
 
     /**
      Monthly ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var monthly: Package?
+    @objc public let monthly: Package?
 
     /**
      Weekly ``Package`` type configured in the RevenueCat dashboard, if available.
      */
-    @objc private(set) public var weekly: Package?
+    @objc public let weekly: Package?
 
     public override var description: String {
         return """
@@ -114,55 +114,50 @@ import Foundation
         self.serverDescription = serverDescription
         self.availablePackages = availablePackages
 
+        var foundPackages: [PackageType: Package] = [:]
+
+        var lifetime: Package?
+        var annual: Package?
+        var sixMonth: Package?
+        var threeMonth: Package?
+        var twoMonth: Package?
+        var monthly: Package?
+        var weekly: Package?
+
         for package in availablePackages {
+            Self.checkForNilAndLogReplacement(previousPackages: foundPackages, newPackage: package)
+
             switch package.packageType {
-            case .lifetime:
-                Self.checkForNilAndLogReplacement(package: self.lifetime, newPackage: package)
-                self.lifetime = package
-            case .annual:
-                Self.checkForNilAndLogReplacement(package: self.annual, newPackage: package)
-                self.annual = package
-            case .sixMonth:
-                Self.checkForNilAndLogReplacement(package: self.sixMonth, newPackage: package)
-                self.sixMonth = package
-            case .threeMonth:
-                Self.checkForNilAndLogReplacement(package: self.threeMonth, newPackage: package)
-                self.threeMonth = package
-            case .twoMonth:
-                Self.checkForNilAndLogReplacement(package: self.twoMonth, newPackage: package)
-                self.twoMonth = package
-            case .monthly:
-                Self.checkForNilAndLogReplacement(package: self.monthly, newPackage: package)
-                self.monthly = package
-            case .weekly:
-                Self.checkForNilAndLogReplacement(package: self.weekly, newPackage: package)
-                self.weekly = package
+            case .lifetime: lifetime = package
+            case .annual: annual = package
+            case .sixMonth: sixMonth = package
+            case .threeMonth: threeMonth = package
+            case .twoMonth: twoMonth = package
+            case .monthly: monthly = package
+            case .weekly: weekly = package
             case .custom where package.storeProduct.productCategory == .nonSubscription:
                 // Non-subscription product, ignoring
-                break
+                continue
             case .unknown, .custom:
                 Logger.warn(
                     "Unknown subscription length for package '\(package.offeringIdentifier)': " +
                     "\(package.packageType). Ignoring."
                 )
+                continue
             }
-        }
-    }
 
-    private static func checkForNilAndLogReplacement(package: Package?, newPackage: Package) {
-        guard let package = package else {
-            return
+            foundPackages[package.packageType] = package
         }
 
-        Logger.warn("Package: \(package.identifier) already exists, overwriting with:\(newPackage.identifier)")
-    }
+        self.lifetime = lifetime
+        self.annual = annual
+        self.sixMonth = sixMonth
+        self.threeMonth = threeMonth
+        self.twoMonth = twoMonth
+        self.monthly = monthly
+        self.weekly = weekly
 
-    private func valueOrEmpty<T: CustomStringConvertible>(_ value: T?) -> String {
-        if let value = value {
-            return value.description
-        } else {
-            return ""
-        }
+        super.init()
     }
 
 }
@@ -173,3 +168,21 @@ extension Offering: Identifiable {
     public var id: String { return self.identifier }
 
 }
+
+extension Offering: Sendable {}
+
+// MARK: - Private
+
+private extension Offering {
+
+    static func checkForNilAndLogReplacement(previousPackages: [PackageType: Package], newPackage: Package) {
+        if let package = previousPackages[newPackage.packageType] {
+            Logger.warn("Package: \(package.identifier) already exists, overwriting with: \(newPackage.identifier)")
+        }
+    }
+
+}
+
+private func valueOrEmpty<T: CustomStringConvertible>(_ value: T?) -> String {
+    return value?.description ?? ""
+}

Sources/Purchasing/Package.swift

@@ -23,7 +23,7 @@ import Foundation
 /// - ``Offering``
 /// - ``Offerings``
 ///
-@objc(RCPackage) public class Package: NSObject {
+@objc(RCPackage) public final class Package: NSObject {
 
     /// The identifier for this Package.
     @objc public let identifier: String
@@ -105,3 +105,5 @@ extension Package: Identifiable {
     public var id: String { return self.identifier }
 
 }
+
+extension Package: Sendable {}

Sources/Purchasing/PackageType.swift

@@ -44,6 +44,8 @@ import Foundation
 
 extension PackageType: CaseIterable {}
 
+extension PackageType: Sendable {}
+
 extension PackageType: CustomDebugStringConvertible {
 
     /// A textual description of the type suitable for debugging.

Sources/Purchasing/StoreKitAbstractions/SK1StoreProduct.swift

@@ -96,3 +96,8 @@ extension SK1StoreProduct: Hashable {
     }
 
 }
+
+#if swift(<5.7)
+// `SK1Product` isn't `Sendable` until iOS 16.0 / Swift 5.7
+extension SK1StoreProduct: @unchecked Sendable {}
+#endif

Sources/Purchasing/StoreKitAbstractions/SK1StoreProductDiscount.swift

@@ -61,6 +61,14 @@ internal struct SK1StoreProductDiscount: StoreProductDiscountType {
 
 }
 
+#if swift(<5.7)
+// `SK1ProductDiscount` isn't `Sendable` until iOS 16.0 / Swift 5.7
+@available(iOS 11.2, macOS 10.13.2, tvOS 11.2, watchOS 6.2, *)
+extension SK1StoreProductDiscount: @unchecked Sendable {}
+#endif
+
+// MARK: - Private
+
 private extension StoreProductDiscount.PaymentMode {
 
     @available(iOS 11.2, macOS 10.13.2, tvOS 11.2, watchOS 6.2, *)

Sources/Purchasing/StoreKitAbstractions/SK2StoreProduct.swift

@@ -116,3 +116,9 @@ extension SK2StoreProduct: Hashable {
     }
 
 }
+
+#if swift(<5.7)
+// `SK2Product` isn't `Sendable` until iOS 16.0 / Swift 5.7
+@available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
+extension SK2StoreProduct: @unchecked Sendable {}
+#endif

Sources/Purchasing/StoreKitAbstractions/SK2StoreProductDiscount.swift

@@ -46,6 +46,14 @@ internal struct SK2StoreProductDiscount: StoreProductDiscountType {
     var localizedPriceString: String { underlyingSK2Discount.displayPrice }
 }
 
+#if swift(<5.7)
+// `SK2ProductDiscount` isn't `Sendable` until iOS 16.0 / Swift 5.7
+@available(iOS 15.0, tvOS 15.0, watchOS 8.0, macOS 12.0, *)
+extension SK2StoreProductDiscount: @unchecked Sendable {}
+#endif
+
+// MARK: - Private
+
 private extension StoreProductDiscount.PaymentMode {
 
     @available(iOS 15.0, tvOS 15.0, macOS 12.0, watchOS 8.0, *)

Sources/Purchasing/StoreKitAbstractions/StoreProduct.swift

@@ -99,7 +99,7 @@ public typealias SK2Product = StoreKit.Product
 }
 
 /// Type that provides access to all of `StoreKit`'s product type's properties.
-internal protocol StoreProductType {
+internal protocol StoreProductType: Sendable {
 
     /// The category of this product, whether a subscription or a one-time purchase.
 

Sources/Purchasing/StoreKitAbstractions/StoreProductDiscount.swift

@@ -98,6 +98,10 @@ public final class StoreProductDiscount: NSObject, StoreProductDiscountType {
 
 }
 
+extension StoreProductDiscount: Sendable {}
+extension StoreProductDiscount.PaymentMode: Sendable {}
+extension StoreProductDiscount.DiscountType: Sendable {}
+
 public extension StoreProductDiscount {
 
     /// The discount price of the product in the local currency.
@@ -136,7 +140,7 @@ extension StoreProductDiscount {
 }
 
 /// The details of an introductory offer or a promotional offer for an auto-renewable subscription.
-internal protocol StoreProductDiscountType {
+internal protocol StoreProductDiscountType: Sendable {
 
     // Note: this is only `nil` for SK1 products before iOS 12.2.
     // It can become `String` once it's not longer supported.

Sources/Purchasing/StoreKitAbstractions/SubscriptionPeriod.swift

@@ -18,7 +18,7 @@ import StoreKit
 /// Use the value and the unit together to determine the subscription period.
 /// For example, if the unit is  `.month`, and the value is `3`, the subscription period is three months.
 @objc(RCSubscriptionPeriod)
-public class SubscriptionPeriod: NSObject {
+public final class SubscriptionPeriod: NSObject {
 
     /// The number of period units.
     @objc public let value: Int
@@ -98,6 +98,9 @@ public extension SubscriptionPeriod {
 
 }
 
+extension SubscriptionPeriod.Unit: Sendable {}
+extension SubscriptionPeriod: Sendable {}
+
 extension SubscriptionPeriod {
     func pricePerMonth(withTotalPrice price: Decimal) -> Decimal {
         let periodsPerMonth: Decimal = {