gh-97930: Apply changes from importlib_resources 5.12. (GH-102010)

Lib/importlib/resources/readers.py

@@ -1,11 +1,12 @@
 import collections
-import operator
+import itertools
 import pathlib
+import operator
 import zipfile
 
 from . import abc
 
-from ._itertools import unique_everseen
+from ._itertools import only
 
 
 def remove_duplicates(items):
@@ -41,8 +42,10 @@ class ZipReader(abc.TraversableResources):
             raise FileNotFoundError(exc.args[0])
 
     def is_resource(self, path):
-        # workaround for `zipfile.Path.is_file` returning true
-        # for non-existent paths.
+        """
+        Workaround for `zipfile.Path.is_file` returning true
+        for non-existent paths.
+        """
         target = self.files().joinpath(path)
         return target.is_file() and target.exists()
 
@@ -67,8 +70,10 @@ class MultiplexedPath(abc.Traversable):
             raise NotADirectoryError('MultiplexedPath only supports directories')
 
     def iterdir(self):
-        files = (file for path in self._paths for file in path.iterdir())
-        return unique_everseen(files, key=operator.attrgetter('name'))
+        children = (child for path in self._paths for child in path.iterdir())
+        by_name = operator.attrgetter('name')
+        groups = itertools.groupby(sorted(children, key=by_name), key=by_name)
+        return map(self._follow, (locs for name, locs in groups))
 
     def read_bytes(self):
         raise FileNotFoundError(f'{self} is not a file')
@@ -90,6 +95,25 @@ class MultiplexedPath(abc.Traversable):
             # Just return something that will not exist.
             return self._paths[0].joinpath(*descendants)
 
+    @classmethod
+    def _follow(cls, children):
+        """
+        Construct a MultiplexedPath if needed.
+
+        If children contains a sole element, return it.
+        Otherwise, return a MultiplexedPath of the items.
+        Unless one of the items is not a Directory, then return the first.
+        """
+        subdirs, one_dir, one_file = itertools.tee(children, 3)
+
+        try:
+            return only(one_dir)
+        except ValueError:
+            try:
+                return cls(*subdirs)
+            except NotADirectoryError:
+                return next(one_file)
+
     def open(self, *args, **kwargs):
         raise FileNotFoundError(f'{self} is not a file')