[in_app_purchase_storekit] Add support for quantity in consumable product purchases (#171570) (#9698)

This PR adds support for specifying a `quantity` when purchasing **consumable** products using StoreKit 2 in the `in_app_purchase_storekit` package.

#### ✅ What’s changing

* Introduces logic to read the `quantity` field from `PurchaseParam` and insert it into the native StoreKit 2 `.purchase(options:)` call.
* Ensures this logic is only applied to consumable products.
* Adds null checks and default behavior to maintain compatibility with purchases that don’t specify quantity.

#### 🧪 Testing

* Added unit tests to verify quantity handling in `Sk2PurchaseParam`:
  * ✅ Verifies that a custom quantity is passed correctly to native purchase options.
  * ✅ Ensures that quantity defaults to `1` when not explicitly provided.
* Tests cover `buyConsumable` flows using `fakeStoreKit2Platform`.
* Verified on a real device using StoreKit 2 with different `quantity` values.
* Ensures no change to StoreKit 1 flow or other product types.

#### 📌 Fixes

Fix [#171570](flutter/flutter#171570)

Author: nikunjrCybage

packages/in_app_purchase/in_app_purchase_storekit/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.4.4
+
+* Added support for specifying quantity in `SK2ProductPurchaseOptions` (consumable purchases on iOS).
+
 ## 0.4.3
 
 * Adds **Introductory Offer Eligibility** support for StoreKit2

packages/in_app_purchase/in_app_purchase_storekit/darwin/in_app_purchase_storekit/Sources/in_app_purchase_storekit/StoreKit2/InAppPurchasePlugin+StoreKit2.swift

@@ -60,6 +60,9 @@ extension InAppPurchasePlugin: InAppPurchase2API {
         {
           purchaseOptions.insert(.appAccountToken(accountTokenUUID))
         }
+        if let quantity = options?.quantity {
+          purchaseOptions.insert(.quantity(Int(quantity)))
+        }
 
         if #available(iOS 17.4, macOS 14.4, *) {
           if let promotionalOffer = options?.promotionalOffer {

packages/in_app_purchase/in_app_purchase_storekit/pubspec.yaml

@@ -2,7 +2,7 @@ name: in_app_purchase_storekit
 description: An implementation for the iOS and macOS platforms of the Flutter `in_app_purchase` plugin. This uses the StoreKit Framework.
 repository: https://github.com/flutter/packages/tree/main/packages/in_app_purchase/in_app_purchase_storekit
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+in_app_purchase%22
-version: 0.4.3
+version: 0.4.4
 
 environment:
   sdk: ^3.6.0

packages/in_app_purchase/in_app_purchase_storekit/test/in_app_purchase_storekit_2_platform_test.dart

@@ -260,6 +260,42 @@ void main() {
       expect(lastPurchaseOptions.winBackOfferId, isNull);
       expect(lastPurchaseOptions.promotionalOffer, isNull);
     });
+
+    test('should pass quantity for consumable product with Sk2PurchaseParam',
+        () async {
+      final Sk2PurchaseParam purchaseParam = Sk2PurchaseParam(
+        productDetails:
+            AppStoreProduct2Details.fromSK2Product(dummyProductWrapper),
+        quantity: 3,
+        applicationUserName: 'testUser',
+      );
+
+      await iapStoreKitPlatform.buyConsumable(purchaseParam: purchaseParam);
+
+      final SK2ProductPurchaseOptionsMessage lastPurchaseOptions =
+          fakeStoreKit2Platform.lastPurchaseOptions!;
+
+      expect(lastPurchaseOptions.appAccountToken, 'testUser');
+      expect(lastPurchaseOptions.quantity, 3);
+      expect(lastPurchaseOptions.winBackOfferId, isNull);
+      expect(lastPurchaseOptions.promotionalOffer, isNull);
+    });
+
+    test('should default to quantity = 1 when not provided in Sk2PurchaseParam',
+        () async {
+      final Sk2PurchaseParam purchaseParam = Sk2PurchaseParam(
+        productDetails:
+            AppStoreProduct2Details.fromSK2Product(dummyProductWrapper),
+        applicationUserName: 'testUser',
+      );
+
+      await iapStoreKitPlatform.buyConsumable(purchaseParam: purchaseParam);
+
+      final SK2ProductPurchaseOptionsMessage lastPurchaseOptions =
+          fakeStoreKit2Platform.lastPurchaseOptions!;
+
+      expect(lastPurchaseOptions.quantity, 1);
+    });
   });
 
   group('restore purchases', () {