Use HasField to check explicit field presedence (#140)

Author: matthias-wende-frequenz

RELEASE_NOTES.md

@@ -1,17 +1,10 @@
 # Frequenz Electricity Trading API Client Release Notes
 
-## Summary
-
-<!-- Here goes a general summary of what this release is about -->
-
-## Upgrading
-
-<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
-
 ## New Features
 
 - Update to API v0.7.0
 
 ## Bug Fixes
 
 - Ensure timestamp conversion errors are surfaced
+- Use HasField to check explicit field precedence

src/frequenz/client/electricity_trading/_types.py

@@ -2002,16 +2002,20 @@ def from_pb(
         Returns:
             PublicOrder object corresponding to the protobuf message.
         """
+        execution_option = (
+            OrderExecutionOption.from_pb(public_order.execution_option)
+            if public_order.HasField("execution_option")
+            else None
+        )
+
         return cls(
             public_order_id=public_order.id,
             delivery_area=DeliveryArea.from_pb(public_order.delivery_area),
             delivery_period=DeliveryPeriod.from_pb(public_order.delivery_period),
             side=MarketSide.from_pb(public_order.side),
             price=Price.from_pb(public_order.price),
             quantity=Power.from_pb(public_order.quantity),
-            execution_option=OrderExecutionOption.from_pb(
-                public_order.execution_option
-            ),
+            execution_option=execution_option,
             create_time=public_order.create_time.ToDatetime(tzinfo=timezone.utc),
             update_time=public_order.update_time.ToDatetime(tzinfo=timezone.utc),
         )