Is there any way to have a route handler that can return both a Stream or a str?

[danechitoaie]

Here's my code

from asyncio import sleep
from collections.abc import AsyncGenerator
from starlite import Starlite, Stream, get
from starlite import BackgroundTask

TEXT = "Hello World!"


async def my_generator() -> AsyncGenerator[str, None]:
    for c in TEXT:
        await sleep(1)
        yield str(c)


@get(path="/stream")
def stream_time(s: bool = False) -> Stream | str:
    return Stream(iterator=my_generator(), media_type="text/plain") if s else TEXT


app = Starlite(route_handlers=[stream_time], debug=True)

I'd like to either stream the response or to just return it directly as a str based on the s query param.
Any way to do this? As current code throws the following error:

Traceback (most recent call last):
  File "/usr/local/Cellar/[email protected]/3.11.0/Frameworks/Python.framework/Versions/3.11/lib/python3.11/multiprocessing/process.py", line 314, in _bootstrap
    self.run()
  File "/usr/local/Cellar/[email protected]/3.11.0/Frameworks/Python.framework/Versions/3.11/lib/python3.11/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/uvicorn/_subprocess.py", line 76, in subprocess_started
    target(sockets=sockets)
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/uvicorn/server.py", line 59, in run
    return asyncio.run(self.serve(sockets=sockets))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Cellar/[email protected]/3.11.0/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/local/Cellar/[email protected]/3.11.0/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "uvloop/loop.pyx", line 1517, in uvloop.loop.Loop.run_until_complete
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/uvicorn/server.py", line 66, in serve
    config.load()
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/uvicorn/config.py", line 471, in load
    self.loaded_app = import_from_string(self.app)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/uvicorn/importer.py", line 21, in import_from_string
    module = importlib.import_module(module_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Cellar/[email protected]/3.11.0/Frameworks/Python.framework/Versions/3.11/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1206, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1178, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1149, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 690, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 940, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/Users/daniels/Work/wingman-api/wingman_app/main3.py", line 20, in <module>
    app = Starlite(route_handlers=[stream_time], debug=True)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/app.py", line 390, in __init__
    self.update_openapi_schema()
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/app.py", line 732, in update_openapi_schema
    self.openapi_schema = construct_open_api_with_schema_class(
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/pydantic_openapi_schema/utils/utils.py", line 53, in construct_open_api_with_schema_class
    schema_definitions = schema(schema_classes, ref_prefix=REF_PREFIX, by_alias=by_alias)["definitions"]
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pydantic/schema.py", line 147, in pydantic.schema.schema
  File "pydantic/schema.py", line 582, in pydantic.schema.model_process_schema
  File "pydantic/schema.py", line 623, in pydantic.schema.model_type_schema
  File "pydantic/schema.py", line 256, in pydantic.schema.field_schema
  File "pydantic/schema.py", line 528, in pydantic.schema.field_type_schema
  File "pydantic/schema.py", line 853, in pydantic.schema.field_singleton_schema
  File "pydantic/schema.py", line 748, in pydantic.schema.field_singleton_sub_fields_schema
  File "pydantic/schema.py", line 528, in pydantic.schema.field_type_schema
  File "pydantic/schema.py", line 952, in pydantic.schema.field_singleton_schema
ValueError: Value not declarable with JSON Schema, field: name='background_BackgroundTask' type=BackgroundTask required=True

I tried added include_in_schema=False and now I'm getting a different error:

Traceback (most recent call last):
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/utils/serialization.py", line 161, in encode_json
    return _msgspec_json_encoder.encode(obj)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/utils/serialization.py", line 120, in default_serializer
    raise TypeError(f"Unsupported type: {type(value)!r}")
TypeError: Unsupported type: <class 'async_generator'>

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/middleware/exceptions/middleware.py", line 50, in __call__
    await self.app(scope, receive, send)
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/routes/http.py", line 79, in handle
    response = await self._get_response_for_request(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/routes/http.py", line 131, in _get_response_for_request
    response = await self._call_handler_function(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/routes/http.py", line 167, in _call_handler_function
    else await route_handler.to_response(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/handlers/http.py", line 660, in to_response
    return await response_handler(app=app, data=data, plugins=plugins, request=request)  # type: ignore
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/handlers/http.py", line 236, in handler
    return await create_response(data=data)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/handlers/http.py", line 206, in create_response
    response = response_class(
               ^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/response/base.py", line 119, in __init__
    self.body = content if isinstance(content, bytes) else self.render(content)
                                                           ^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/response/base.py", line 286, in render
    return encode_json(content, self._enc_hook)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/daniels/Work/wingman-api/.venv/lib/python3.11/site-packages/starlite/utils/serialization.py", line 164, in encode_json
    raise SerializationException(str(msgspec_error)) from msgspec_error
starlite.exceptions.base_exceptions.SerializationException: Unsupported type: <class 'async_generator'>

[Goldziher]

Hi. This is not supported. The reason is that we precompute the routes to ensure performance and this will make this very complex.