fix: stock-snapshots api and service calc wrong result

stock/services.py

@@ -815,7 +815,6 @@ def create_stock_snapshot(stock_change_detail: models.StockChangeDetail, invento
         raise ValueError("无效的库存变动明细记录")
 
     delta = stock_change_detail.quantity if stock_change_detail.stock_change_record.is_incoming else -stock_change_detail.quantity
-    rolls_delta = 1 if stock_change_detail.stock_change_record.is_incoming else -1
 
     # 必须在库存变动发生后创建快照
     snapshot = models.StockSnapshot(
@@ -827,7 +826,7 @@ def create_stock_snapshot(stock_change_detail: models.StockChangeDetail, invento
         quantity_after=inventory.quantity,
         stock_change_record_id=stock_change_detail.stock_change_record.id,
         unit=stock_change_detail.unit,
-        num_of_rolls=inventory.num_of_rolls + rolls_delta,
+        num_of_rolls=inventory.num_of_rolls,
     )
     snapshot.save()
     logger.info(

stock/tests.py

@@ -241,6 +241,7 @@ class CreateStockSnapshotTestCase(StockServicesTestCase):
         self.assertEqual(snapshot.delta, 100)  # 入库数量为正
         self.assertEqual(snapshot.quantity_before, 50)  # 150 - 100
         self.assertEqual(snapshot.quantity_after, 150)
+        self.assertEqual(snapshot.num_of_rolls, self.inventory.num_of_rolls)
         self.assertEqual(snapshot.stock_change_record_id, self.stock_change_in.id)
         
         # 验证日志调用
@@ -257,6 +258,7 @@ class CreateStockSnapshotTestCase(StockServicesTestCase):
         self.assertEqual(snapshot.delta, -50)  # 出库数量为负
         self.assertEqual(snapshot.quantity_before, 200)  # 150 - (-50)
         self.assertEqual(snapshot.quantity_after, 150)
+        self.assertEqual(snapshot.num_of_rolls, self.inventory.num_of_rolls)
     
     def test_create_snapshot_with_invalid_detail(self):
         """测试使用无效明细记录创建快照"""