fix(json): Fix composed type (oneOf) serialization returning empty object

[sh3r4rd]

Summary

This PR fixes a bug where composed types (oneOf/union types) would serialize to {} instead of the actual object content when using write_object_value(None, value).

Problem

When serializing composed types (oneOf wrappers/union types), the write_object_value method was incorrectly using temp_writer.writer (which is empty for composed types) instead of temp_writer.value (which contains the serialized content).

Example of the bug

Given a composed type like:

@dataclass
class StepInput(ComposedTypeWrapper, Parsable):
    step_input_question_variant: Optional[StepInputQuestionVariant] = None
    step_input_statement_variant: Optional[StepInputStatementVariant] = None
    
    def serialize(self, writer: SerializationWriter) -> None:
        if self.step_input_question_variant:
            writer.write_object_value(None, self.step_input_question_variant)
        elif self.step_input_statement_variant:
            writer.write_object_value(None, self.step_input_statement_variant)

When serializing, the output would be {} instead of the actual variant content like {"kind": "question", "header": "...", ...}.

Root cause

In write_object_value, when value.serialize(temp_writer) is called:

• For regular objects with properties, data is written to temp_writer.writer (a dict with keys)
• For composed types that call write_object_value(None, inner_value), data is written to temp_writer.value

The original code always used temp_writer.writer:

if key:
    self.writer[key] = temp_writer.writer
else:
    self.value = temp_writer.writer  # Bug: should check temp_writer.value first

Solution

Check if temp_writer.value is available (for composed types) and fall back to temp_writer.writer (for regular objects):

serialized_value = temp_writer.value if temp_writer.value is not None else temp_writer.writer
if key:
    self.writer[key] = serialized_value
else:
    self.value = serialized_value

Testing

• Added test case test_write_composed_type_with_no_key that verifies composed types serialize correctly
• All existing tests pass
• Tested against a real API with oneOf discriminated unions (Blooming Health Screenings API)

Impact

This bug affects any API that uses oneOf discriminated unions in request bodies. Without this fix, the serialized JSON is empty ({}), causing API validation errors.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud