Revert "Remove importlib-metadata and importlib-resources"

This reverts commit 38435ae81c.

lib/importlib_resources/abc.py

@@ -0,0 +1,170 @@
+import abc
+import io
+import itertools
+import pathlib
+from typing import Any, BinaryIO, Iterable, Iterator, NoReturn, Text, Optional
+
+from ._compat import runtime_checkable, Protocol, StrPath
+
+
+__all__ = ["ResourceReader", "Traversable", "TraversableResources"]
+
+
+class ResourceReader(metaclass=abc.ABCMeta):
+    """Abstract base class for loaders to provide resource reading support."""
+
+    @abc.abstractmethod
+    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
+
+    @abc.abstractmethod
+    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
+
+    @abc.abstractmethod
+    def is_resource(self, path: Text) -> bool:
+        """Return True if the named 'path' is a resource.
+
+        Files are resources, directories are not.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def contents(self) -> Iterable[str]:
+        """Return an iterable of entries in `package`."""
+        raise FileNotFoundError
+
+
+class TraversalError(Exception):
+    pass
+
+
+@runtime_checkable
+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.
+    """
+
+    @abc.abstractmethod
+    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()
+
+    @abc.abstractmethod
+    def is_dir(self) -> bool:
+        """
+        Return True if self is a directory
+        """
+
+    @abc.abstractmethod
+    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)
+
+    @abc.abstractmethod
+    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.
+        """
+
+    @property
+    @abc.abstractmethod
+    def name(self) -> str:
+        """
+        The base name of this object without any parent references.
+        """
+
+
+class TraversableResources(ResourceReader):
+    """
+    The required interface for providing traversable
+    resources.
+    """
+
+    @abc.abstractmethod
+    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())