fix(json): preserve empty property names during serialization

packages/abstractions/kiota_abstractions/multipart_body.py

@@ -154,7 +154,7 @@ def _write_parsable(self, writer, part_value) -> None:
                 part_value[0]
             )
         )
-        part_writer.write_object_value("", part_value[1], None)
+        part_writer.write_object_value(None, part_value[1], None)
         part_content = part_writer.get_serialized_content()
         if hasattr(part_content, "seek"):  # seekable
             part_content.seek(0)

packages/serialization/json/kiota_serialization_json/json_serialization_writer.py

@@ -38,7 +38,7 @@ def write_str_value(self, key: Optional[str], value: Optional[str]) -> None:
             value (Optional[str]): The string value to be written.
         """
         if isinstance(value, str):
-            if key:
+            if key is not None:
                 self.writer[key] = value
             else:
                 self.value = value
@@ -50,7 +50,7 @@ def write_bool_value(self, key: Optional[str], value: Optional[bool]) -> None:
             value (Optional[bool]): The boolean value to be written.
         """
         if isinstance(value, bool):
-            if key:
+            if key is not None:
                 self.writer[key] = value
             else:
                 self.value = value
@@ -62,7 +62,7 @@ def write_int_value(self, key: Optional[str], value: Optional[int]) -> None:
             value (Optional[int]): The integer value to be written.
         """
         if isinstance(value, int):
-            if key:
+            if key is not None:
                 self.writer[key] = value
             else:
                 self.value = value
@@ -74,7 +74,7 @@ def write_float_value(self, key: Optional[str], value: Optional[float]) -> None:
             value (Optional[float]): The float value to be written.
         """
         if isinstance(value, (float, int)):
-            if key:
+            if key is not None:
                 self.writer[key] = float(value)
             else:
                 self.value = float(value)
@@ -86,19 +86,19 @@ def write_uuid_value(self, key: Optional[str], value: Optional[UUID]) -> None:
             value (Optional[UUID]): The uuid value to be written.
         """
         if isinstance(value, UUID):
-            if key:
+            if key is not None:
                 self.writer[key] = str(value)
             else:
                 self.value = str(value)
         elif isinstance(value, str):
             try:
                 UUID(value)
-                if key:
+                if key is not None:
                     self.writer[key] = value
                 else:
                     self.value = value
             except ValueError:
-                if key:
+                if key is not None:
                     raise ValueError(f"Invalid UUID string value found for property {key}")
                 raise ValueError("Invalid UUID string value found")
 
@@ -109,19 +109,19 @@ def write_datetime_value(self, key: Optional[str], value: Optional[datetime]) ->
             value (Optional[datetime]): The datetime offset value to be written.
         """
         if isinstance(value, datetime):
-            if key:
+            if key is not None:
                 self.writer[key] = value.isoformat()
             else:
                 self.value = value.isoformat()
         elif isinstance(value, str):
             try:
                 datetime.fromisoformat(value)
-                if key:
+                if key is not None:
                     self.writer[key] = value
                 else:
                     self.value = value
             except ValueError:
-                if key:
+                if key is not None:
                     raise ValueError(f"Invalid datetime string value found for property {key}")
                 raise ValueError("Invalid datetime string value found")
 
@@ -132,19 +132,19 @@ def write_timedelta_value(self, key: Optional[str], value: Optional[timedelta])
             value (Optional[timedelta]): The timedelta value to be written.
         """
         if isinstance(value, timedelta):
-            if key:
+            if key is not None:
                 self.writer[key] = str(value)
             else:
                 self.value = str(value)
         elif isinstance(value, str):
             try:
                 parse_timedelta_string(value)
-                if key:
+                if key is not None:
                     self.writer[key] = value
                 else:
                     self.value = value
             except ValueError:
-                if key:
+                if key is not None:
                     raise ValueError(f"Invalid timedelta string value found for property {key}")
                 raise ValueError("Invalid timedelta string value found")
 
@@ -155,19 +155,19 @@ def write_date_value(self, key: Optional[str], value: Optional[date]) -> None:
             value (Optional[date]): The date value to be written.
         """
         if isinstance(value, date):
-            if key:
+            if key is not None:
                 self.writer[key] = str(value)
             else:
                 self.value = str(value)
         elif isinstance(value, str):
             try:
                 date.fromisoformat(value)
-                if key:
+                if key is not None:
                     self.writer[key] = value
                 else:
                     self.value = value
             except ValueError:
-                if key:
+                if key is not None:
                     raise ValueError(f"Invalid date string value found for property {key}")
                 raise ValueError("Invalid date string value found")
 
@@ -178,19 +178,19 @@ def write_time_value(self, key: Optional[str], value: Optional[time]) -> None:
             value (Optional[time]): The time value to be written.
         """
         if isinstance(value, time):
-            if key:
+            if key is not None:
                 self.writer[key] = str(value)
             else:
                 self.value = str(value)
         elif isinstance(value, str):
             try:
                 time.fromisoformat(value)
-                if key:
+                if key is not None:
                     self.writer[key] = value
                 else:
                     self.value = value
             except ValueError:
-                if key:
+                if key is not None:
                     raise ValueError(f"Invalid time string value found for property {key}")
                 raise ValueError("Invalid time string value found")
 
@@ -210,7 +210,7 @@ def write_collection_of_primitive_values(
                 temp_writer.write_any_value(None, val)
                 result.append(temp_writer.value)
 
-            if key:
+            if key is not None:
                 self.writer[key] = result
             else:
                 self.value = result
@@ -231,7 +231,7 @@ def write_collection_of_object_values(
                 temp_writer.write_object_value(None, val)
                 obj_list.append(temp_writer.value)
 
-            if key:
+            if key is not None:
                 self.writer[key] = obj_list
             else:
                 self.value = obj_list
@@ -251,7 +251,7 @@ def write_collection_of_enum_values(
                 temp_writer.write_enum_value(None, val)
                 result.append(temp_writer.value)
 
-            if key:
+            if key is not None:
                 self.writer[key] = result
             else:
                 self.value = result
@@ -273,7 +273,7 @@ def __write_collection_of_dict_values(
                 temp_writer.__write_dict_value(None, val)
                 result.append(temp_writer.value)
 
-            if key:
+            if key is not None:
                 self.writer[key] = result
             else:
                 self.value = result
@@ -288,7 +288,7 @@ def write_bytes_value(self, key: Optional[str], value: Optional[bytes]) -> None:
         if isinstance(value, bytes):
             base64_bytes = base64.b64encode(value)
             base64_string = base64_bytes.decode('utf-8')
-            if key:
+            if key is not None:
                 self.writer[key] = base64_string
             else:
                 self.value = base64_string
@@ -323,7 +323,7 @@ def write_object_value(
             serialized_value = (
                 temp_writer.value if temp_writer.value is not None else temp_writer.writer
             )
-            if key:
+            if key is not None:
                 self.writer[key] = serialized_value
             else:
                 self.value = serialized_value
@@ -335,7 +335,7 @@ def write_enum_value(self, key: Optional[str], value: Optional[K]) -> None:
             value (Optional[K]): The enum value to be written.
         """
         if isinstance(value, Enum):
-            if key:
+            if key is not None:
                 self.writer[key] = value.value
             else:
                 self.value = value.value
@@ -345,7 +345,7 @@ def write_null_value(self, key: Optional[str]) -> None:
         Args:
             key (Optional[str]): The key to be used for the written value. May be null.
         """
-        if key:
+        if key is not None:
             self.writer[key] = None
         else:
             self.value = None
@@ -360,7 +360,7 @@ def __write_dict_value(self, key: Optional[str], value: dict[str, Any]) -> None:
             temp_writer: JsonSerializationWriter = self._create_new_writer()
             for dict_key, dict_value in value.items():
                 temp_writer.write_any_value(dict_key, dict_value)
-            if key:
+            if key is not None:
                 self.writer[key] = temp_writer.writer
             else:
                 self.value = temp_writer.writer
@@ -459,7 +459,7 @@ def write_non_parsable_object_value(self, key: Optional[str], value: T) -> None:
             value (object): The value to be written.
         """
         if hasattr(value, '__dict__'):
-            if key:
+            if key is not None:
                 self.writer[key] = value.__dict__
             else:
                 self.value = value.__dict__

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

@@ -0,0 +1,53 @@
+import json
+from datetime import date, datetime, time, timedelta
+from uuid import UUID
+
+import pytest
+
+from kiota_serialization_json.json_serialization_writer import JsonSerializationWriter
+
+from ..helpers import OfficeLocation, User
+
+
+@pytest.mark.parametrize("key", ["", "named", None])
+@pytest.mark.parametrize("method,value,expected", [
+    ("write_str_value", "text", "text"),
+    ("write_bool_value", True, True),
+    ("write_int_value", 42, 42),
+    ("write_float_value", 1.5, 1.5),
+    ("write_uuid_value", UUID(int=1), str(UUID(int=1))),
+    ("write_datetime_value", datetime(2026, 1, 2, 3, 4), "2026-01-02T03:04:00"),
+    ("write_date_value", date(2026, 1, 2), "2026-01-02"),
+    ("write_time_value", time(3, 4), "03:04:00"),
+    ("write_timedelta_value", timedelta(seconds=1), "0:00:01"),
+    ("write_bytes_value", b"hello", "aGVsbG8="),
+    ("write_collection_of_primitive_values", [1, 2], [1, 2]),
+    ("write_enum_value", OfficeLocation.Oval, "oval"),
+    ("write_collection_of_enum_values", [OfficeLocation.Oval], ["oval"]),
+])
+def test_property_name_is_distinct_from_root(key, method, value, expected):
+    writer = JsonSerializationWriter()
+    getattr(writer, method)(key, value)
+    assert json.loads(writer.get_serialized_content()) == (
+        expected if key is None else {key: expected}
+    )
+
+
+@pytest.mark.parametrize("value", [None, "", False, 0, {}, {"": {}}, [{"": "value"}]])
+def test_nested_additional_data_preserves_empty_names(value):
+    writer = JsonSerializationWriter()
+    writer.write_additional_data_value({"properties": {"": value}})
+    assert json.loads(writer.get_serialized_content()) == {"properties": {"": value}}
+
+
+@pytest.mark.parametrize("collection", [False, True])
+def test_model_with_empty_property_name(collection):
+    user = User()
+    user.mobile_phone = "123"
+    writer = JsonSerializationWriter()
+    if collection:
+        writer.write_collection_of_object_values("", [user])
+    else:
+        writer.write_object_value("", user)
+    expected = {"mobile_phone": "123"}
+    assert json.loads(writer.get_serialized_content()) == {"": [expected] if collection else expected}