support deferring win-back storekit messages

Sources/Purchasing/Configuration.swift

@@ -195,8 +195,9 @@ import Foundation
         }
 
         /// Set `showStoreMessagesAutomatically`. Enabled by default.
-        /// If enabled, if the user has billing issues, has yet to accept a price increase consent or
-        /// there are other messages from StoreKit, they will be displayed automatically when the app is initialized.
+        /// If enabled, if the user has billing issues, has yet to accept a price increase consent, is eligible for a
+        /// win-back offer, or there are other messages from StoreKit, they will be displayed automatically when
+        /// the app is initialized.
         ///
         /// If you want to disable this behavior so that you can customize when these messages are shown, make sure
         /// you configure the SDK as early as possible in the app's lifetime, otherwise messages will be displayed

Sources/Support/StoreMessageType.swift

@@ -21,10 +21,17 @@ import StoreKit
 
     /// Message shown when there are billing issues in a subscription
     case billingIssue = 0
+
     /// Message shown when there is a price increase in a subscription that requires consent
     case priceIncreaseConsent
+
     /// Generic Store messages
     case generic
+
+    /// Message shown when a subscriber is eligible to redeem a win-back offer that you've
+    /// configured in App Store Connect. More information can be found
+    /// [here](https://developer.apple.com/documentation/storekit/message/reason/4418230-winbackoffer).
+    case winBackOffer
 }
 
 #if os(iOS) || targetEnvironment(macCatalyst) || VISION_OS
@@ -40,6 +47,14 @@ extension Message.Reason {
         case .priceIncreaseConsent: return .priceIncreaseConsent
         case .generic: return .generic
         default:
+            // winBackOffer message reason was added in iOS 18.0, but it's not recognized by xcode versions <16.0.
+            // https://developer.apple.com/documentation/xcode-release-notes/xcode-14_3-release-notes
+            #if compiler(>=6.0)
+            if #available(iOS 18.0, visionOS 2.0, *), case .winBackOffer = self {
+                return .winBackOffer
+            }
+            #endif
+
             // billingIssue message reason was added in iOS 16.4, but it's not recognized by older xcode versions.
             // https://developer.apple.com/documentation/xcode-release-notes/xcode-14_3-release-notes
             #if swift(>=5.8)

Tests/StoreKitUnitTests/StoreMessageTypeTests.swift

@@ -36,6 +36,12 @@ class StoreMessagesTypeTests: TestCase {
         #endif
         expect(Message.Reason.priceIncreaseConsent.messageType) == .priceIncreaseConsent
         expect(Message.Reason.generic.messageType) == .generic
+
+        #if compiler(>=6.0)
+        if #available(iOS 18.0, visionOS 2.0, *) {
+            expect(Message.Reason.winBackOffer.messageType) == .winBackOffer
+        }
+        #endif
     }
 
 }