perf(hooks): extract restorePurchases into useCallback for stable reference (#3172)

## Summary

Extracts the inline `restorePurchases` function from the `useIAP` hook's
return statement into a properly memoized `useCallback`.

## Problem

All other public functions returned by `useIAP` (e.g.
`finishTransaction`, `requestPurchase`, `fetchProducts`,
`validateReceipt`) are wrapped in `useCallback` to provide a stable
reference across renders. However, `restorePurchases` was defined as an
inline `async () => {}` directly in the return statement, causing it to
be recreated on every render.

This inconsistency means:
- Components that receive `restorePurchases` as a prop and use it in a
`useEffect` or `useCallback` dependency array will trigger unnecessary
re-runs
- Strict mode linting (e.g. `react-hooks/exhaustive-deps`) can flag its
usage since it's not stable
- It's inconsistent with the rest of the hook's API surface

## Changes
- Extracted `restorePurchases` into a `useCallback` with appropriate
dependencies `[getAvailablePurchasesInternal, invokeOnError]`
- Removed the now-outdated comment `// No local restorePurchases; use
the top-level helper via returned API`
- The return statement now references the stable `restorePurchases`
variable

## Why
Improves performance consistency and aligns `restorePurchases` with the
rest of the hook's API design.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
* Updated restore flow: on iOS the app now performs a platform sync
before refreshing purchases. No change to public API or expected
behavior for end users.
* **Tests**
* Test suite updated to reflect the new iOS restore sequence and error
propagation scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyochan

src/__tests__/hooks/useIAP.test.ts

@@ -44,7 +44,7 @@ describe('hooks/useIAP (renderer)', () => {
   let mockGetAvailablePurchases: jest.SpyInstance;
   let mockGetActiveSubscriptions: jest.SpyInstance;
   let mockHasActiveSubscriptions: jest.SpyInstance;
-  let mockRestorePurchases: jest.SpyInstance;
+  let mockSyncIOS: jest.SpyInstance;
 
   beforeEach(() => {
     jest.spyOn(IAP, 'initConnection').mockResolvedValue(true as any);
@@ -61,8 +61,8 @@ describe('hooks/useIAP (renderer)', () => {
     mockFetchProducts = jest
       .spyOn(IAP, 'fetchProducts')
       .mockResolvedValue([] as any);
-    mockRestorePurchases = jest
-      .spyOn(IAP, 'restorePurchases')
+    mockSyncIOS = jest
+      .spyOn(IAP, 'syncIOS')
       .mockResolvedValue(undefined as any);
     jest.spyOn(IAP, 'purchaseUpdatedListener').mockImplementation((cb: any) => {
       capturedPurchaseListener = cb;
@@ -240,9 +240,9 @@ describe('hooks/useIAP (renderer)', () => {
       expect(onError).toHaveBeenCalledWith(hasSubsError);
     });
 
-    it('calls onError when restorePurchases fails', async () => {
+    it('calls onError when restorePurchases fails (syncIOS error on iOS)', async () => {
       const restoreError = new Error('Failed to restore');
-      mockRestorePurchases.mockRejectedValueOnce(restoreError);
+      mockSyncIOS.mockRejectedValueOnce(restoreError);
 
       let api: any;
       const onError = jest.fn();
@@ -260,9 +260,53 @@ describe('hooks/useIAP (renderer)', () => {
         await api.restorePurchases();
       });
 
+      expect(mockSyncIOS).toHaveBeenCalled();
       expect(onError).toHaveBeenCalledWith(restoreError);
     });
 
+    it('calls onError when restorePurchases fails (getAvailablePurchases error)', async () => {
+      const purchaseError = new Error('Failed to get purchases after restore');
+      mockGetAvailablePurchases.mockRejectedValueOnce(purchaseError);
+
+      let api: any;
+      const onError = jest.fn();
+      const Harness = () => {
+        api = useIAP({onError});
+        return null;
+      };
+
+      await act(async () => {
+        TestRenderer.create(React.createElement(Harness));
+      });
+      await act(async () => {});
+
+      await act(async () => {
+        await api.restorePurchases();
+      });
+
+      expect(onError).toHaveBeenCalledWith(purchaseError);
+    });
+
+    it('restorePurchases calls syncIOS then getAvailablePurchases on iOS', async () => {
+      let api: any;
+      const Harness = () => {
+        api = useIAP();
+        return null;
+      };
+
+      await act(async () => {
+        TestRenderer.create(React.createElement(Harness));
+      });
+      await act(async () => {});
+
+      await act(async () => {
+        await api.restorePurchases();
+      });
+
+      expect(mockSyncIOS).toHaveBeenCalled();
+      expect(mockGetAvailablePurchases).toHaveBeenCalled();
+    });
+
     it('does not call onError when operations succeed', async () => {
       let api: any;
       const onError = jest.fn();

src/hooks/useIAP.ts

@@ -18,7 +18,7 @@ import {
   verifyPurchaseWithProvider as verifyPurchaseWithProviderTopLevel,
   getActiveSubscriptions,
   hasActiveSubscriptions,
-  restorePurchases as restorePurchasesTopLevel,
+  syncIOS,
   getPromotedProductIOS,
   requestPurchaseOnPromotedProductIOS,
   checkAlternativeBillingAvailabilityAndroid,
@@ -333,7 +333,18 @@ export function useIAP(options?: UseIapOptions): UseIap {
     [],
   );
 
-  // No local restorePurchases; use the top-level helper via returned API
+  const restorePurchases = useCallback(async (): Promise<void> => {
+    try {
+      if (Platform.OS === 'ios') {
+        await syncIOS();
+      }
+
+      await getAvailablePurchasesInternal();
+    } catch (error) {
+      RnIapConsole.warn('Failed to restore purchases:', error);
+      invokeOnError(error);
+    }
+  }, [getAvailablePurchasesInternal, invokeOnError]);
 
   const validateReceipt = useCallback(
     async (options: VerifyPurchaseProps): Promise<VerifyPurchaseResult> =>
@@ -506,15 +517,7 @@ export function useIAP(options?: UseIapOptions): UseIap {
     validateReceipt,
     verifyPurchase,
     verifyPurchaseWithProvider,
-    restorePurchases: async () => {
-      try {
-        await restorePurchasesTopLevel();
-        await getAvailablePurchasesInternal();
-      } catch (error) {
-        RnIapConsole.warn('Failed to restore purchases:', error);
-        invokeOnError(error);
-      }
-    },
+    restorePurchases,
     getPromotedProductIOS,
     requestPurchaseOnPromotedProductIOS,
     getActiveSubscriptions: getActiveSubscriptionsInternal,