A utility to confirm "or None" types are not None

[hunterhogan]

We all have to deal with return values that are "X | None" and the type checker assumes the value is None until we prove it is not None. Sometimes, I want to raise an exception if the value is None, such as:

importlibSpecification = importlib.util.spec_from_file_location(pathFilename.stem, pathFilename)
if importlibSpecification is None:
    raise ImportError

I want to reduce code duplication with a simple utility. Perhaps the syntax would be like

importlibSpecification = raiseIfNone(importlib.util.spec_from_file_location(pathFilename.stem, pathFilename), ImportError)

I feel like a real programmer must have already come up with ways to handle this situation, whether with a function or something else. What options are there?

hunterhogan/mapFolding#3

[sobolevn]

def raise_if_none[T](obj: T | None) -> T:
    if obj is None:
        raise TypeError('message')
    return obj

I think that this 3-line-function is easy enough to be just written, when you need it 🤔

[hunterhogan]

Thank you. The following seems to be working well.

def raiseIfNone[TypeSansNone](returnTarget: TypeSansNone | None) -> TypeSansNone:
	if returnTarget is None:
		raise ValueError('Return is None.')
	return returnTarget