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Merge pull request #183 from python/feature/90-low-level-reader
Implement a low-level interface for loaders to implement instead of TraversableResources
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""" | ||
Interface adapters for low-level readers. | ||
""" | ||
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import abc | ||
import io | ||
import itertools | ||
from typing import BinaryIO, List | ||
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from .abc import Traversable, TraversableResources | ||
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class SimpleReader(abc.ABC): | ||
""" | ||
The minimum, low-level interface required from a resource | ||
provider. | ||
""" | ||
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@abc.abstractproperty | ||
def package(self): | ||
# type: () -> str | ||
""" | ||
The name of the package for which this reader loads resources. | ||
""" | ||
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@abc.abstractmethod | ||
def children(self): | ||
# type: () -> List['SimpleReader'] | ||
""" | ||
Obtain an iterable of SimpleReader for available | ||
child containers (e.g. directories). | ||
""" | ||
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@abc.abstractmethod | ||
def resources(self): | ||
# type: () -> List[str] | ||
""" | ||
Obtain available named resources for this virtual package. | ||
""" | ||
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@abc.abstractmethod | ||
def open_binary(self, resource): | ||
# type: (str) -> BinaryIO | ||
""" | ||
Obtain a File-like for a named resource. | ||
""" | ||
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@property | ||
def name(self): | ||
return self.package.split('.')[-1] | ||
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class ResourceHandle(Traversable): | ||
""" | ||
Handle to a named resource in a ResourceReader. | ||
""" | ||
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def __init__(self, parent, name): | ||
# type: (ResourceContainer, str) -> None | ||
self.parent = parent | ||
self.name = name # type: ignore | ||
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def is_file(self): | ||
return True | ||
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def is_dir(self): | ||
return False | ||
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def open(self, mode='r', *args, **kwargs): | ||
stream = self.parent.reader.open_binary(self.name) | ||
if 'b' not in mode: | ||
stream = io.TextIOWrapper(*args, **kwargs) | ||
return stream | ||
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def joinpath(self, name): | ||
raise RuntimeError("Cannot traverse into a resource") | ||
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class ResourceContainer(Traversable): | ||
""" | ||
Traversable container for a package's resources via its reader. | ||
""" | ||
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def __init__(self, reader): | ||
# type: (SimpleReader) -> None | ||
self.reader = reader | ||
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def is_dir(self): | ||
return True | ||
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def is_file(self): | ||
return False | ||
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def iterdir(self): | ||
files = (ResourceHandle(self, name) for name in self.reader.resources) | ||
dirs = map(ResourceContainer, self.reader.children()) | ||
return itertools.chain(files, dirs) | ||
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def open(self, *args, **kwargs): | ||
raise IsADirectoryError() | ||
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def joinpath(self, name): | ||
return next( | ||
traversable for traversable in self.iterdir() if traversable.name == name | ||
) | ||
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class TraversableReader(TraversableResources, SimpleReader): | ||
""" | ||
A TraversableResources based on SimpleReader. Resource providers | ||
may derive from this class to provide the TraversableResources | ||
interface by supplying the SimpleReader interface. | ||
""" | ||
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def files(self): | ||
return ResourceContainer(self) |