jaraco · May 8, 2020 · Apr 26, 2020 · Apr 27, 2020 · Apr 28, 2020 · May 8, 2020
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
@@ -480,6 +480,8 @@ ABC hierarchy::
 
 .. class:: ResourceReader
 
+    *Superseded by TraversableReader*
+
     An :term:`abstract base class` to provide the ability to read
     *resources*.
 
@@ -795,6 +797,28 @@ ABC hierarchy::
         itself does not end in ``__init__``.
 
 
+.. class:: Traversable
+
+    An object with a subset of pathlib.Path methods suitable for
+    traversing directories and opening files.
+
+    .. versionadded:: 3.9
+
+
+.. class:: TraversableReader
+
+    An abstract base class for resource readers capable of serving
+    the ``files`` interface. Subclasses ResourceReader and provides
+    concrete implementations of the ResourceReader's abstract
+    methods. Therefore, any loader supplying TraversableReader
+    also supplies ResourceReader.
+
+    Loaders that wish to support resource reading are expected to
+    implement this interface.
+
+    .. versionadded:: 3.9
+
+
 :mod:`importlib.resources` -- Resources
 ---------------------------------------
 
@@ -853,6 +877,19 @@ The following types are defined.
 
 The following functions are available.
 
+
+.. function:: files(package)
+
+    Returns an :class:`importlib.resources.abc.Traversable` object
+    representing the resource container for the package (think directory)
+    and its resources (think files). A Traversable may contain other
+    containers (think subdirectories).
+
+    *package* is either a name or a module object which conforms to the
+    ``Package`` requirements.
+
+    .. versionadded:: 3.9
+
 .. function:: open_binary(package, resource)
 
     Open for binary reading the *resource* within *package*.

diff --git a/Lib/importlib/_common.py b/Lib/importlib/_common.py
@@ -0,0 +1,72 @@
+import os
+import pathlib
+import zipfile
+import tempfile
+import functools
+import contextlib
+
+
+def from_package(package):
+    """
+    Return a Traversable object for the given package.
+
+    """
+    spec = package.__spec__
+    return from_traversable_resources(spec) or fallback_resources(spec)
+
+
+def from_traversable_resources(spec):
+    """
+    If the spec.loader implements TraversableResources,
+    directly or implicitly, it will have a ``files()`` method.
+    """
+    with contextlib.suppress(AttributeError):
+        return spec.loader.files()
+
+
+def fallback_resources(spec):
+    package_directory = pathlib.Path(spec.origin).parent
+    try:
+        archive_path = spec.loader.archive
+        rel_path = package_directory.relative_to(archive_path)
+        return zipfile.Path(archive_path, str(rel_path) + '/')
+    except Exception:
+        pass
+    return package_directory
+
+
+@contextlib.contextmanager
+def _tempfile(reader, suffix=''):
+    # Not using tempfile.NamedTemporaryFile as it leads to deeper 'try'
+    # blocks due to the need to close the temporary file to work on Windows
+    # properly.
+    fd, raw_path = tempfile.mkstemp(suffix=suffix)
+    try:
+        os.write(fd, reader())
+        os.close(fd)
+        yield pathlib.Path(raw_path)
+    finally:
+        try:
+            os.remove(raw_path)
+        except FileNotFoundError:
+            pass
+
+
+@functools.singledispatch
+@contextlib.contextmanager
+def as_file(path):
+    """
+    Given a Traversable object, return that object as a
+    path on the local file system in a context manager.
+    """
+    with _tempfile(path.read_bytes, suffix=path.name) as local:
+        yield local
+
+
+@as_file.register(pathlib.Path)
+@contextlib.contextmanager
+def _(path):
+    """
+    Degenerate behavior for pathlib.Path objects.
+    """
+    yield path
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
@@ -14,6 +14,7 @@
     _frozen_importlib_external = _bootstrap_external
 import abc
 import warnings
+from typing import Protocol, runtime_checkable
 
 
 def _register(abstract_cls, *classes):
@@ -386,3 +387,88 @@ def contents(self):
 
 
 _register(ResourceReader, machinery.SourceFileLoader)
+
+
+@runtime_checkable
+class Traversable(Protocol):
+    """
+    An object with a subset of pathlib.Path methods suitable for
+    traversing directories and opening files.
+    """
+
+    @abc.abstractmethod
+    def iterdir(self):
+        """
+        Yield Traversable objects in self
+        """
+
+    @abc.abstractmethod
+    def read_bytes(self):
+        """
+        Read contents of self as bytes
+        """
+
+    @abc.abstractmethod
+    def read_text(self, encoding=None):
+        """
+        Read contents of self as bytes
+        """
+
+    @abc.abstractmethod
+    def is_dir(self):
+        """
+        Return True if self is a dir
+        """
+
+    @abc.abstractmethod
+    def is_file(self):
+        """
+        Return True if self is a file
+        """
+
+    @abc.abstractmethod
+    def joinpath(self, child):
+        """
+        Return Traversable child in self
+        """
+
+    @abc.abstractmethod
+    def __truediv__(self, child):
+        """
+        Return Traversable child in self
+        """
+
+    @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.
+        """
+
+    @abc.abstractproperty
+    def name(self):
+        # type: () -> str
+        """
+        The base name of this object without any parent references.
+        """
+
+
+class TraversableResources(ResourceReader):
+    @abc.abstractmethod
+    def files(self):
+        """Return a Traversable object for the loaded package."""
+
+    def open_resource(self, resource):
+        return self.files().joinpath(resource).open('rb')
+
+    def resource_path(self, resource):
+        raise FileNotFoundError(resource)
+
+    def is_resource(self, path):
+        return self.files().joinpath(path).isfile()
+
+    def contents(self):
+        return (item.name for item in self.files().iterdir())