[3.12] gh-113188: Fix shutil.copymode() and shutil.copystat() on Windows (GH-113285)

Previously they worked differenly if dst is a symbolic link:
they modified the permission bits of dst itself rather than the file
it points to if follow_symlinks is true or src is not a symbolic link,
and did nothing if follow_symlinks is false and src is a symbolic link.

1 files changed, 14 insertions, 2 deletions

diff --git a/Lib/shutil.py b/Lib/shutil.py
index b99614f..e026088 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -302,11 +302,15 @@ def copymode(src, dst, *, follow_symlinks=True):
     sys.audit("shutil.copymode", src, dst)
 
     if not follow_symlinks and _islink(src) and os.path.islink(dst):
-        if hasattr(os, 'lchmod'):
+        if os.name == 'nt':
+            stat_func, chmod_func = os.lstat, os.chmod
+        elif hasattr(os, 'lchmod'):
             stat_func, chmod_func = os.lstat, os.lchmod
         else:
             return
     else:
+        if os.name == 'nt' and os.path.islink(dst):
+            dst = os.path.realpath(dst, strict=True)
         stat_func, chmod_func = _stat, os.chmod
 
     st = stat_func(src)
@@ -382,8 +386,16 @@ def copystat(src, dst, *, follow_symlinks=True):
     # We must copy extended attributes before the file is (potentially)
     # chmod()'ed read-only, otherwise setxattr() will error with -EACCES.
     _copyxattr(src, dst, follow_symlinks=follow)
+    _chmod = lookup("chmod")
+    if os.name == 'nt':
+        if follow:
+            if os.path.islink(dst):
+                dst = os.path.realpath(dst, strict=True)
+        else:
+            def _chmod(*args, **kwargs):
+                os.chmod(*args)
     try:
-        lookup("chmod")(dst, mode, follow_symlinks=follow)
+        _chmod(dst, mode, follow_symlinks=follow)
     except NotImplementedError:
         # if we got a NotImplementedError, it's because
         #   * follow_symlinks=False,