Exceptions

Exceptions used by the FastIoC library.

FastIoCError

Bases: Exception

Base class for all exceptions raised by the FastIoC library. Allows users to catch all FastIoC-related errors with a single except clause.

SingletonGeneratorError

Bases: FastIoCError

Raised when attempting to register a generator or async generator as a singleton dependency in the DI container.

Generator objects cannot be used more than once - reusing them would raise an error. Therefore, singleton scope does not make sense here.

SingletonLifetimeViolationError

Bases: FastIoCError

Raised when a singleton dependency attempts to depend on a scoped or transient dependency.

This violates lifetime rules because singleton instances live for the entire process/worker lifetime, while scoped and transient instances are created per request or per resolution. Injecting shorter-lived dependencies into a singleton may lead to captured request state, invalid references, or memory leaks.

UnregisteredProtocolError

Bases: FastIoCError

Raised when a requested protocol, interface, or service has not been registered in the container.