`Hardfork` doesn't respect `base` when importing sub-modules

[SamWilsn]

What was wrong?

The Hardfork class allows specifying a base path to search for modules:

execution-specs/src/ethereum_spec_tools/forks.py

Line 65 in ea802a0

def discover(cls: Type[H], base: Optional[PurePath] = None) -> List[H]:

It also provides methods for importing submodules of discovered forks:

execution-specs/src/ethereum_spec_tools/forks.py

Lines 274 to 303 in ea802a0

	def import_module(self) -> ModuleType:
	"""
	Return the module containing this specification.
	"""
	return self.mod
	def module(self, name: str) -> Any:
	"""
	Import if necessary, and return the given module belonging to this hard
	fork.
	"""
	return importlib.import_module(self.mod.__name__ + "." + name)
	def iter_modules(self) -> Iterator[ModuleInfo]:
	"""
	Iterate through the (sub-)modules describing this hardfork.
	"""
	if self.path is None:
	raise ValueError(f"cannot walk {self.name}, path is None")
	return pkgutil.iter_modules(self.path, self.name + ".")
	def walk_packages(self) -> Iterator[ModuleInfo]:
	"""
	Iterate recursively through the (sub-)modules describing this hardfork.
	"""
	if self.path is None:
	raise ValueError(f"cannot walk {self.name}, path is None")
	return pkgutil.walk_packages([self.path], self.name + ".")

Unfortunately, Hardfork doesn't consider base when importing those submodules. It just relies on the default import machinery.

How can it be fixed?

Use spec_from_file_location and module_from_spec when loading submodules.