fix(json): give on_start the object's own writer and pass the hooks to nested parse nodes

packages/serialization/json/kiota_serialization_json/json_parse_node.py

@@ -351,7 +351,7 @@ def _assign_field_values(self, item: Parsable) -> None:
                 if field_value is None:
                     continue
                 field_deserializer = field_deserializers[field_name]
-                field_deserializer(JsonParseNode(field_value))
+                field_deserializer(self._create_new_node(field_value))
             elif item_additional_data is not None:
                 item_additional_data[field_name] = self.try_get_anything(field_value)
             else:

packages/serialization/json/kiota_serialization_json/json_serialization_writer.py

@@ -519,7 +519,7 @@ def _serialize_value(self, temp_writer: JsonSerializationWriter, value: U) -> No
         if on_before := self.on_before_object_serialization:
             on_before(value)
         if on_start := self.on_start_object_serialization:
-            on_start(value, self)
+            on_start(value, temp_writer)
 
         value.serialize(temp_writer)
 

packages/serialization/json/tests/helpers/__init__.py

@@ -1,4 +1,5 @@
 from .entity import Entity
 from .office_location import OfficeLocation
+from .team import Team
 from .user import User
 from .user2 import User2

packages/serialization/json/tests/helpers/team.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from collections.abc import Callable
+from typing import Optional
+
+from kiota_abstractions.serialization import Parsable, ParseNode, SerializationWriter
+
+from .user import User
+
+
+@dataclass
+class Team(Parsable):
+    lead: Optional[User] = None
+
+    @staticmethod
+    def create_from_discriminator_value(parse_node: Optional[ParseNode] = None) -> Team:
+        return Team()
+
+    def get_field_deserializers(self) -> dict[str, Callable[[ParseNode], None]]:
+        return {"lead": lambda n: setattr(self, 'lead', n.get_object_value(User))}
+
+    def serialize(self, writer: SerializationWriter) -> None:
+        writer.write_object_value("lead", self.lead)

packages/serialization/json/tests/unit/test_json_parse_node.py

@@ -4,7 +4,7 @@
 
 import pytest
 from kiota_serialization_json.json_parse_node import JsonParseNode
-from ..helpers import OfficeLocation, User
+from ..helpers import OfficeLocation, Team, User
 
 
 def test_get_str_value():
@@ -363,3 +363,13 @@ def test_get_collection_of_object_values(users_json):
     assert result[0].business_phones == ["+1 205 555 0108"]
     assert result[0].is_active is True
     assert result[0].mobile_phone is None
+
+
+def test_hooks_run_for_nested_objects():
+    seen = []
+    parse_node = JsonParseNode(json.loads('{"lead": {"mobile_phone": "+1 234 567 891"}}'))
+    parse_node.on_before_assign_field_values = lambda value: seen.append(type(value).__name__)
+    parse_node.on_after_assign_field_values = lambda value: seen.append(type(value).__name__)
+    team = parse_node.get_object_value(Team)
+    assert team.lead.mobile_phone == "+1 234 567 891"
+    assert seen == ["Team", "User", "User", "Team"]

packages/serialization/json/tests/unit/test_json_serialization_writer.py

@@ -6,7 +6,7 @@
 
 from kiota_serialization_json.json_serialization_writer import JsonSerializationWriter
 
-from ..helpers import OfficeLocation, User, User2
+from ..helpers import OfficeLocation, Team, User, User2
 
 
 @pytest.fixture
@@ -353,3 +353,25 @@ def test_write_composed_type_with_no_key(user_1):
     # The union type should serialize the inner user object, not an empty object
     assert content_string == '{"id": "8f841f30-e6e3-439a-a812-ebd369559c36", '\
         '"updated_at": "2022-01-27T12:59:45.596117+00:00", "is_active": true}'
+
+
+def clear_is_active(value, writer):
+    if isinstance(value, User):
+        writer.write_null_value("is_active")
+
+
+def test_on_start_writes_into_the_root_object():
+    json_serialization_writer = JsonSerializationWriter()
+    json_serialization_writer.on_start_object_serialization = clear_is_active
+    json_serialization_writer.write_object_value(None, User(mobile_phone="+1 234 567 891"))
+    content = json_serialization_writer.get_serialized_content()
+    assert json.loads(content) == {"is_active": None, "mobile_phone": "+1 234 567 891"}
+
+
+def test_on_start_writes_into_the_nested_object():
+    json_serialization_writer = JsonSerializationWriter()
+    json_serialization_writer.on_start_object_serialization = clear_is_active
+    team = Team(lead=User(mobile_phone="+1 234 567 891"))
+    json_serialization_writer.write_object_value(None, team)
+    content = json_serialization_writer.get_serialized_content()
+    assert json.loads(content) == {"lead": {"is_active": None, "mobile_phone": "+1 234 567 891"}}