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import abc | |
import io | |
import itertools | |
import pathlib | |
from typing import Any, BinaryIO, Iterable, Iterator, NoReturn, Text, Optional | |
from typing import runtime_checkable, Protocol | |
from .compat.py38 import StrPath | |
__all__ = ["ResourceReader", "Traversable", "TraversableResources"] | |
class ResourceReader(metaclass=abc.ABCMeta): | |
"""Abstract base class for loaders to provide resource reading support.""" | |
def open_resource(self, resource: Text) -> BinaryIO: | |
"""Return an opened, file-like object for binary reading. | |
The 'resource' argument is expected to represent only a file name. | |
If the resource cannot be found, FileNotFoundError is raised. | |
""" | |
# This deliberately raises FileNotFoundError instead of | |
# NotImplementedError so that if this method is accidentally called, | |
# it'll still do the right thing. | |
raise FileNotFoundError | |
def resource_path(self, resource: Text) -> Text: | |
"""Return the file system path to the specified resource. | |
The 'resource' argument is expected to represent only a file name. | |
If the resource does not exist on the file system, raise | |
FileNotFoundError. | |
""" | |
# This deliberately raises FileNotFoundError instead of | |
# NotImplementedError so that if this method is accidentally called, | |
# it'll still do the right thing. | |
raise FileNotFoundError | |
def is_resource(self, path: Text) -> bool: | |
"""Return True if the named 'path' is a resource. | |
Files are resources, directories are not. | |
""" | |
raise FileNotFoundError | |
def contents(self) -> Iterable[str]: | |
"""Return an iterable of entries in `package`.""" | |
raise FileNotFoundError | |
class TraversalError(Exception): | |
pass | |
class Traversable(Protocol): | |
""" | |
An object with a subset of pathlib.Path methods suitable for | |
traversing directories and opening files. | |
Any exceptions that occur when accessing the backing resource | |
may propagate unaltered. | |
""" | |
def iterdir(self) -> Iterator["Traversable"]: | |
""" | |
Yield Traversable objects in self | |
""" | |
def read_bytes(self) -> bytes: | |
""" | |
Read contents of self as bytes | |
""" | |
with self.open('rb') as strm: | |
return strm.read() | |
def read_text(self, encoding: Optional[str] = None) -> str: | |
""" | |
Read contents of self as text | |
""" | |
with self.open(encoding=encoding) as strm: | |
return strm.read() | |
def is_dir(self) -> bool: | |
""" | |
Return True if self is a directory | |
""" | |
def is_file(self) -> bool: | |
""" | |
Return True if self is a file | |
""" | |
def joinpath(self, *descendants: StrPath) -> "Traversable": | |
""" | |
Return Traversable resolved with any descendants applied. | |
Each descendant should be a path segment relative to self | |
and each may contain multiple levels separated by | |
``posixpath.sep`` (``/``). | |
""" | |
if not descendants: | |
return self | |
names = itertools.chain.from_iterable( | |
path.parts for path in map(pathlib.PurePosixPath, descendants) | |
) | |
target = next(names) | |
matches = ( | |
traversable for traversable in self.iterdir() if traversable.name == target | |
) | |
try: | |
match = next(matches) | |
except StopIteration: | |
raise TraversalError( | |
"Target not found during traversal.", target, list(names) | |
) | |
return match.joinpath(*names) | |
def __truediv__(self, child: StrPath) -> "Traversable": | |
""" | |
Return Traversable child in self | |
""" | |
return self.joinpath(child) | |
def open(self, mode='r', *args, **kwargs): | |
""" | |
mode may be 'r' or 'rb' to open as text or binary. Return a handle | |
suitable for reading (same as pathlib.Path.open). | |
When opening as text, accepts encoding parameters such as those | |
accepted by io.TextIOWrapper. | |
""" | |
def name(self) -> str: | |
""" | |
The base name of this object without any parent references. | |
""" | |
class TraversableResources(ResourceReader): | |
""" | |
The required interface for providing traversable | |
resources. | |
""" | |
def files(self) -> "Traversable": | |
"""Return a Traversable object for the loaded package.""" | |
def open_resource(self, resource: StrPath) -> io.BufferedReader: | |
return self.files().joinpath(resource).open('rb') | |
def resource_path(self, resource: Any) -> NoReturn: | |
raise FileNotFoundError(resource) | |
def is_resource(self, path: StrPath) -> bool: | |
return self.files().joinpath(path).is_file() | |
def contents(self) -> Iterator[str]: | |
return (item.name for item in self.files().iterdir()) | |