Add transactions handler to init method according ios documentation it's important to add handler on application:didFinishLaunchingWithOptions: (https://developer.apple.com/documentation/storekit/in-app_purchase/setting_up_the_transaction_observer_for_the_payment_queue?language=objc), move observable commands to separate queue so it can be processed separately and after listener setup, add IAP_ProcessPendingTransactions function to resolve pending transactions on iOS.

extension-iap/src/iap_emscripten.cpp

@@ -77,6 +77,11 @@ static void IAPList_Callback(void* luacallback, const char* result_json)
     dmScript::TeardownCallback(callback);
 }
 
+static int IAP_ProcessPendingTransactions(lua_State* L)
+{
+    return 0;
+}
+
 static int IAP_List(lua_State* L)
 {
     DM_LUA_STACK_CHECK(L, 0);
@@ -210,6 +215,7 @@ static const luaL_reg IAP_methods[] =
     {"restore", IAP_Restore},
     {"set_listener", IAP_SetListener},
     {"get_provider_id", IAP_GetProviderId},
+    {"process_pending_transactions", IAP_ProcessPendingTransactions},
     {0, 0}
 };