Issue #19856: shutil.move() failed to move a directory to other directory

on Windows if source name ends with os.altsep.

Lib/shutil.py

@@ -483,7 +483,8 @@ def onerror(*args):
 def _basename(path):
     # A basename() variant which first strips the trailing slash, if present.
     # Thus we always get the last component of the path, even for directories.
-    return os.path.basename(path.rstrip(os.path.sep))
+    sep = os.path.sep + (os.path.altsep or '')
+    return os.path.basename(path.rstrip(sep))
 
 def move(src, dst):
     """Recursively move a file or directory to another location. This is

Lib/test/test_shutil.py

@@ -1492,6 +1492,15 @@ def test_move_dir_to_dir_other_fs(self):
         # Move a dir inside an existing dir on another filesystem.
         self.test_move_dir_to_dir()
 
+    def test_move_dir_sep_to_dir(self):
+        self._check_move_dir(self.src_dir + os.path.sep, self.dst_dir,
+            os.path.join(self.dst_dir, os.path.basename(self.src_dir)))
+
+    @unittest.skipUnless(os.path.altsep, 'requires os.path.altsep')
+    def test_move_dir_altsep_to_dir(self):
+        self._check_move_dir(self.src_dir + os.path.altsep, self.dst_dir,
+            os.path.join(self.dst_dir, os.path.basename(self.src_dir)))
+
     def test_existing_file_inside_dest_dir(self):
         # A file with the same name inside the destination dir already exists.
         with open(self.dst_file, "wb"):

Misc/NEWS

@@ -37,6 +37,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #19856: shutil.move() failed to move a directory to other directory
+  on Windows if source name ends with os.altsep.
+
 - Issue #20530: The signatures for slot builtins have been updated
   to reflect the fact that they only accept positional-only arguments.