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UnknownFactoryKwargError

Symptom

modern_di.exceptions.registration.UnknownFactoryKwargError: Factory kwargs contain unknown key(s) not in create_service signature:
  - 'conection_string' (did you mean 'connection_string'?)
Known parameters: ['connection_string']
See: https://modern-di.modern-python.org/troubleshooting/unknown-factory-kwarg-error/

It is raised by the Factory(...) call, before any container exists. Each unknown key gets its own line, in sorted order, with a did you mean hint when a parameter name is close to it. The exception carries .creator, .unknown_keys, .known_keys and .suggestions.

Cause

A key in kwargs={...} matches no parameter of the creator, usually a typo or a key left behind after a parameter was renamed.

The check runs only when modern-di reads the creator's signature. It is skipped when the creator takes **kwargs, when its signature cannot be read, and when the factory sets skip_creator_parsing=True. In the last case a bad key surfaces at resolve time as CreatorCallError.

Fix

Match the kwargs keys to the creator's parameter names.

# Broken:
providers.Factory(create_service, scope=Scope.APP, kwargs={"conection_string": "..."})

# Works:
class Dependencies(Group):
    service = providers.Factory(
        create_service, scope=Scope.APP, kwargs={"connection_string": "..."}
    )


assert isinstance(Container(groups=[Dependencies]).resolve(Service), Service)

See also