bpo-38994: Implement __class_getitem__ for PathLike (GH-17498)

https://bugs.python.org/issue38994

Lib/os.py

@@ -1072,6 +1072,9 @@ class PathLike(abc.ABC):
     def __subclasshook__(cls, subclass):
         return hasattr(subclass, '__fspath__')
 
+    def __class_getitem__(cls, type):
+        return cls
+
 
 if name == 'nt':
     class _AddedDllDirectory:

Lib/pathlib.py

@@ -777,6 +777,9 @@ class PurePath(object):
             return NotImplemented
         return self._cparts >= other._cparts
 
+    def __class_getitem__(cls, type):
+        return cls
+
     drive = property(attrgetter('_drv'),
                      doc="""The drive prefix (letter or UNC path), if any.""")
 

Lib/test/test_os.py

@@ -4048,6 +4048,9 @@ class TestPEP519(unittest.TestCase):
         self.assertRaises(ZeroDivisionError, self.fspath,
                           FakePath(ZeroDivisionError()))
 
+    def test_pathlike_class_getitem(self):
+        self.assertIs(os.PathLike[bytes], os.PathLike)
+
 
 class TimesTests(unittest.TestCase):
     def test_times(self):

Lib/test/test_pathlib.py

@@ -2217,6 +2217,9 @@ class _BasePathTest(object):
 class PathTest(_BasePathTest, unittest.TestCase):
     cls = pathlib.Path
 
+    def test_class_getitem(self):
+        self.assertIs(self.cls[str], self.cls)
+
     def test_concrete_class(self):
         p = self.cls('a')
         self.assertIs(type(p),

Misc/NEWS.d/next/Library/2019-12-07-18-58-44.bpo-38994.IJYhz_.rst

@@ -0,0 +1 @@
+Implement ``__class_getitem__`` for ``os.PathLike``, ``pathlib.Path``