Optional dependencies #336
Description
I am trying to create a container that optionally takes a dependency, and otherwise provides a value derived from another provider. The (IMO) hacky solution I have so far is a custom provider which either provides a Callable, or a default value if the callable has an error. Then I use this with the Callable being the dependency provider.
My questions are (1) is there a better way? and (2) even using this method, DefaultCallable defined below seems like a hack -- how can I improve?
T = TypeVar("T")
class DefaultCallable(providers.Provider):
__slots__ = ("_callable", "_default")
def __init__(
self, callable: Callable[..., T], default: T, *args, **kwargs
):
self._default = default
self._callable = providers.Callable(callable, *args, **kwargs)
super().__init__()
def __deepcopy__(self, memo):
copied = memo.get(id(self))
if copied is not None:
return copied
# TODO: type?
copied = self.__class__(
cast(Callable[..., T], self._callable.provides),
providers.deepcopy(self._default, memo),
*providers.deepcopy(self._callable.args, memo),
**providers.deepcopy(self._callable.kwargs, memo),
)
self._copy_overridings(copied, memo)
return copied
def _provide(self, args, kwargs):
try:
return self._callable(*args, **kwargs)
except Exception:
# TODO: why do we need to check if is provider?
# type?
if getattr(cast(Any, self._default), "__IS_PROVIDER__", False):
return cast(Any, self._default)()
else:
return self._default
# Used like
class Foo(containers.DeclarativeContainer):
#: specify dv for pattern discovery (optional)
dv_in: Provider[xr.DataArray] = providers.Dependency(
instance_of=xr.DataArray
)
#: dv for pattern discovery (specified or default)
dv: Provider[xr.DataArray] = DefaultCallable(
# cast(Callable[..., xr.DataArray], dv_in), type??
cast(Any, dv_in),
problem.training.provided["dv"],
)