from contextlib import suppress
from . import abc
class SpecLoaderAdapter:
"""
Adapt a package spec to adapt the underlying loader.
"""
def __init__(self, spec, adapter=lambda spec: spec.loader):
self.spec = spec
self.loader = adapter(spec)
def __getattr__(self, name):
return getattr(self.spec, name)
class TraversableResourcesLoader:
"""
Adapt a loader to provide TraversableResources.
"""
def __init__(self, spec):
self.spec = spec
def get_resource_reader(self, name):
return DegenerateFiles(self.spec)._native()
class DegenerateFiles:
"""
Adapter for an existing or non-existant resource reader
to provide a degenerate .files().
"""
class Path(abc.Traversable):
def iterdir(self):
return iter(())
def is_dir(self):
return False
is_file = exists = is_dir # type: ignore
def joinpath(self, other):
return DegenerateFiles.Path()
@property
def name(self):
return ''
def open(self, mode='rb', *args, **kwargs):
raise ValueError()
def __init__(self, spec):
self.spec = spec
@property
def _reader(self):
with suppress(AttributeError):
return self.spec.loader.get_resource_reader(self.spec.name)
def _native(self):
"""
Return the native reader if it supports files().
"""
reader = self._reader
return reader if hasattr(reader, 'files') else self
def __getattr__(self, attr):
return getattr(self._reader, attr)
def files(self):
return DegenerateFiles.Path()
def wrap_spec(package):
"""
Construct a package spec with traversable compatibility
on the spec/loader/reader.
"""
return SpecLoaderAdapter(package.__spec__, TraversableResourcesLoader)
