Fix serialization of payloads that contain collection of multiple elements (#637)

Serialization of a payload that contains a collection of items fails.
Only the last item of the collection appears in the
serialized output. All other collections are not available.

Fixes #635

Author: OrangeTux

ocpp/charge_point.py

@@ -130,16 +130,18 @@ class StatusInfoType:
     serialized = asdict(dataclass)
 
     for field in dataclass.__dataclass_fields__.values():
-
         value = getattr(dataclass, field.name)
         if _is_dataclass_instance(value):
             serialized[field.name] = serialize_as_dict(value)
             continue
 
         if isinstance(value, list):
+            serialized[field.name] = []
             for item in value:
                 if _is_dataclass_instance(item):
-                    serialized[field.name] = [serialize_as_dict(item)]
+                    serialized[field.name].append(serialize_as_dict(item))
+                else:
+                    serialized[field.name].append(item)
 
     return serialized
 

tests/test_charge_point.py

@@ -16,6 +16,7 @@
 from ocpp.v16.datatypes import MeterValue, SampledValue
 from ocpp.v16.enums import Action, RegistrationStatus
 from ocpp.v201 import ChargePoint as cp_201
+from ocpp.v201 import call_result, datatypes, enums
 from ocpp.v201.call import GetVariables as v201GetVariables
 from ocpp.v201.call import SetNetworkProfile as v201SetNetworkProfile
 from ocpp.v201.datatypes import (
@@ -312,6 +313,67 @@ def test_serialize_as_dict():
     assert serialize_as_dict(payload) == expected
 
 
+def test_serialization_of_collection_of_multiple_elements():
+    """This test validates that bug #635 is fixed.
+    That bug incorrectly serialized payloads that contain a collection
+    of elements.
+
+    This test serializes a call_result.SetVariables that contains 2
+    SetVariableResultTypes.
+
+    https://github.com/mobilityhouse/ocpp/issues/635
+    """
+    payload = call_result.SetVariables(
+        set_variable_result=[
+            datatypes.SetVariableResultType(
+                attribute_status=enums.SetVariableStatusType.accepted,
+                component={
+                    "name": "TemperatureSensor",
+                    "instance": "First",
+                    "evse": {"id": 1, "connector_id": 1},
+                },
+                variable={"name": "DisplayUnit", "instance": "Main"},
+                attribute_type="Actual",
+                attribute_status_info=None,
+            ),
+            datatypes.SetVariableResultType(
+                attribute_status="Accepted",
+                component={"name": "TxCtrlr"},
+                variable={"name": "TxStopPoint"},
+                attribute_type="Actual",
+                attribute_status_info=None,
+            ),
+        ],
+        custom_data=None,
+    )
+
+    expected = {
+        "custom_data": None,
+        "set_variable_result": [
+            {
+                "attribute_status": "Accepted",
+                "attribute_status_info": None,
+                "attribute_type": "Actual",
+                "component": {
+                    "evse": {"connector_id": 1, "id": 1},
+                    "instance": "First",
+                    "name": "TemperatureSensor",
+                },
+                "variable": {"instance": "Main", "name": "DisplayUnit"},
+            },
+            {
+                "attribute_status": "Accepted",
+                "attribute_status_info": None,
+                "attribute_type": "Actual",
+                "component": {"name": "TxCtrlr"},
+                "variable": {"name": "TxStopPoint"},
+            },
+        ],
+    }
+    # Execute / Assert
+    assert serialize_as_dict(payload) == expected
+
+
 @pytest.mark.asyncio
 async def test_call_unique_id_added_to_handler_args_correctly(connection):
     """