OpenBB-finance/OpenBB · error · TypeError

Error: The {name} instance in '{app_path}' appears not to be

Error message

Error: The {name} instance in '{app_path}' appears not to be a callable factory function

What it means

Raised when --factory was passed and the named attribute was called as app_or_factory() but the call raised TypeError, meaning the attribute is not a zero-argument callable factory function (mirroring uvicorn's config logic).

Source

Thrown at openbb_platform/extensions/platform_api/openbb_platform_api/utils/api.py:295

        raise AttributeError(
            f"Error: The app file '{app_path}' does not contain an '{name}' instance"
        )

    app_or_factory = getattr(module, name)

    # Here we use the same approach as uvicorn to handle factory functions.
    # This prevents us from relying on explicit type annotations.
    # See: https://github.com/encode/uvicorn/blob/master/uvicorn/config.py
    try:
        app = app_or_factory()
        if not factory:
            print(  # noqa: T201
                "\n\n[WARNING]   "
                "App factory detected. Using it, but please consider setting the --factory flag explicitly.\n"
            )
    except TypeError:
        if factory:
            raise TypeError(  # pylint: disable=raise-missing-from
                f"Error: The {name} instance in '{app_path}' appears not to be a callable factory function"
            )
        app = app_or_factory

    if not isinstance(app, FastAPI):
        raise TypeError(
            f"Error: The {name} instance in '{app_path}' is not an instance of FastAPI"
        )

    app.add_middleware(
        CORSMiddleware,
        allow_origins=system.api_settings.cors.allow_origins,
        allow_methods=system.api_settings.cors.allow_methods,
        allow_headers=system.api_settings.cors.allow_headers,
    )

    AppLoader.add_exception_handlers(app)

View on GitHub (pinned to 3e071fcc2c)

Solutions

  1. Drop the --factory flag if the module exposes a ready FastAPI instance.
  2. If a factory is intended, make it zero-argument (wrap configuration inside it) and keep the flag.
  3. Pass the correct --name pointing at the factory function (e.g. 'main:create_app').
  4. Inspect the TypeError chained from the failed call for signature details.

Example fix

# before
# main.py: app = FastAPI()
import_app('main.py', 'app', factory=True)  # TypeError

# after
import_app('main.py', 'app', factory=False)
Defensive patterns

Strategy: validation

Validate before calling

obj = getattr(module, name)
if factory:
    assert callable(obj) and not isinstance(obj, FastAPI), "--factory requires a zero-arg factory function"

Type guard

def is_zero_arg_factory(obj) -> bool:
    import inspect
    return callable(obj) and not inspect.signature(obj).parameters.keys() and not isinstance(obj, FastAPI)

Try / catch

try:
    app = import_app(path, name, factory=True)
except TypeError as e:
    if "callable factory" in str(e):
        app = import_app(path, name, factory=False)  # attribute is an instance, not a factory
    else:
        raise

Prevention

When it happens

Trigger: Running with factory=True where the named attribute is a FastAPI instance (not callable) or a function requiring arguments; calling an object whose __call__ signature needs parameters.

Common situations: Copy-pasting a factory-style command against a module that exports a plain app instance; a create_app(settings) factory that requires an argument; renaming between instance and factory styles.

Related errors

AI-assisted analysis of OpenBB-finance/OpenBB@3e071fcc2c (2026-08-14). Data as JSON: /api/errors/002a200af91db339. Report an issue: GitHub.