bpo-39791: Add files() to importlib.resources (GH-19722)

* bpo-39791: Update importlib.resources to support files() API (importlib_resources 1.5).

* 📜🤖 Added by blurb_it.

* Add some documentation about the new objects added.

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

Lib/importlib/abc.py

@@ -14,6 +14,7 @@ except ImportError:
     _frozen_importlib_external = _bootstrap_external
 import abc
 import warnings
+from typing import Protocol, runtime_checkable
 
 
 def _register(abstract_cls, *classes):
@@ -386,3 +387,88 @@ class ResourceReader(metaclass=abc.ABCMeta):
 
 
 _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())