Serialization problem with DataModel and evaluator suite .add_case method

[marcinwolder-miquido]

There is an issue with JSON serialization of DataModel that contain datetime attribute.

Expected Behavior

There should be a new case in the storage json file.

[
    {
        "identifier": "test",
        "parameters": {
            "date": "2025-09-25T11:42:09.804558"
        }
    }
]

Current Behavior

Draive fails to serialize a DataModel object.

Traceback:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/local/__main__.py", line 28, in <module>
    asyncio.run(main())
    ~~~~~~~~~~~^^^^^^^^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/asyncio/runners.py", line 195, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/asyncio/base_events.py", line 725, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/local/__main__.py", line 24, in main
    await test_evaluator_suite.add_case(test_obj)
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/.venv/lib/python3.13/site-packages/draive/evaluation/suite.py", line 675, in add_case
    await self._cases_storage.save(self._cases_cache)
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/.venv/lib/python3.13/site-packages/draive/evaluation/suite.py", line 930, in save
    await self._file_save(cases)
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/.venv/lib/python3.13/site-packages/haiway/helpers/asynchrony.py", line 113, in asynchronous
    return await (loop or get_running_loop()).run_in_executor(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
    )
    ^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/concurrent/futures/thread.py", line 59, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/Users/marcinwolder/Desktop/repo/Casualty-AI/.venv/lib/python3.13/site-packages/draive/evaluation/suite.py", line 938, in _file_save
    file.write(json.dumps([case.to_mapping() for case in cases]).encode("utf-8"))
               ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/json/encoder.py", line 261, in iterencode
    return _iterencode(o, 0)
  File "/Users/marcinwolder/.local/share/uv/python/cpython-3.13.7-macos-aarch64-none/lib/python3.13/json/encoder.py", line 180, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
                    f'is not JSON serializable')
TypeError: Object of type datetime is not JSON serializable

Possible Solution

DataModel should use its .to_json method before evaluation suite tries to save it.

Steps to Reproduce

1. Create main.py:

   import asyncio
   from collections.abc import Sequence
   from datetime import datetime
   
   from draive import DataModel, Field, ctx
   from draive.evaluation import EvaluatorResult, EvaluatorScenarioResult, evaluator_suite
   
   
   class TestModel(DataModel):
       date: datetime = Field(default=datetime.now())
   
   
   @evaluator_suite(TestModel, storage="test_suite.json")
   async def test_evaluator_suite(
       parameters: TestModel,
   ) -> Sequence[EvaluatorScenarioResult | EvaluatorResult]:
       return []
   
   
   async def main() -> None:
       async with ctx.scope("main"):
           test_obj = TestModel()
           print(test_obj.to_json())  # This prints json with serialized datetime (casted to str)
           await test_evaluator_suite.add_case(test_obj)
   
   
   if __name__ == "__main__":
       asyncio.run(main())

2. Create test_suite.json:

   []

3. Run python3 main.py

Context (Environment)

• python version: 3.13.7
• requirements:

  Package           Version  Editable project location
  ----------------- -------- --------------------------------------------
  annotated-types   0.7.0
  anyio             4.11.0
  asyncpg           0.30.0
  bandit            1.8.6
  casuality         0.1.0    /Users/marcinwolder/Desktop/repo/Casualty-AI
  certifi           2025.8.3
  cffi              2.0.0
  click             8.3.0
  coverage          7.10.7
  cryptography      46.0.1
  distro            1.9.0
  draive            0.85.5
  fastapi-slim      0.117.1
  grpcio            1.75.0
  h11               0.16.0
  h2                4.3.0
  haiway            0.32.0
  hpack             4.1.0
  httpcore          1.0.9
  httpx             0.28.1
  hyperframe        6.1.0
  idna              3.10
  iniconfig         2.1.0
  jiter             0.11.0
  joserfc           1.3.4
  markdown-it-py    4.0.0
  mdurl             0.1.2
  nodeenv           1.9.1
  numpy             2.3.3
  openai            1.108.2
  packaging         25.0
  pillow            11.3.0
  pluggy            1.6.0
  portalocker       3.2.0
  protobuf          6.32.1
  pyaudio           0.2.14
  pycparser         2.23
  pydantic          2.11.9
  pydantic-core     2.33.2
  pygments          2.19.2
  pypdfium2         4.30.0
  pyright           1.1.405
  pytest            8.4.2
  pytest-asyncio    1.2.0
  pytest-cov        7.0.0
  pyyaml            6.0.2
  qdrant-client     1.15.1
  rich              14.1.0
  ruff              0.13.1
  sniffio           1.3.1
  starlette         0.48.0
  stevedore         5.5.0
  tqdm              4.67.1
  typing-extensions 4.15.0
  typing-inspection 0.4.1
  urllib3           2.5.0
  uvicorn           0.36.0
  websocket-client  1.8.0
  websockets        15.0.1