gh-59616: Support os.chmod(follow_symlinks=True) and os.lchmod() on Windows

Doc/library/os.rst

@@ -2062,6 +2062,7 @@ features:
  Although Windows supports :func:`chmod`, you can only set the file's
  read-only flag with it (via the ``stat.S_IWRITE`` and ``stat.S_IREAD``
  constants or a corresponding integer value). All other bits are ignored.
+ The default value of *follow_symlinks* is ``False`` on Windows.
 
  The function is limited on Emscripten and WASI, see
  :ref:`wasm-availability` for more information.
@@ -2075,6 +2076,9 @@ features:
  .. versionchanged:: 3.6
  Accepts a :term:`path-like object`.
 
+ .. versionchanged:: 3.13
+ Added support for the *follow_symlinks* argument on Windows.
+
 
 .. function:: chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True)
 
@@ -2165,11 +2169,14 @@ features:
 
  .. audit-event:: os.chmod path,mode,dir_fd os.lchmod
 
- .. availability:: Unix, not Linux, FreeBSD >= 1.3, NetBSD >= 1.3, not OpenBSD
+ .. availability:: Unix, Windows, not Linux, FreeBSD >= 1.3, NetBSD >= 1.3, not OpenBSD
 
  .. versionchanged:: 3.6
  Accepts a :term:`path-like object`.
 
+ .. versionchanged:: 3.13
+ Added support on Windows.
+
 .. function:: lchown(path, uid, gid)
 
  Change the owner and group id of *path* to the numeric *uid* and *gid*. This

Doc/whatsnew/3.13.rst

@@ -261,6 +261,12 @@ os
  CPU resources of a container system without having to modify the container (application code).
  (Contributed by Donghee Na in :gh:`109595`)
 
+* Add support of :func:`os.lchmod` and the *follow_symlinks* argument
+ in :func:`os.chmod` on Windows.
+ Note that the default value of *follow_symlinks* in :func:`!os.lchmod` is
+ ``False`` on Windows.
+ (Contributed by Serhiy Storchaka in :gh:`59616`)
+
 pathlib
 -------
 

Lib/os.py

@@ -171,6 +171,7 @@ def _add(str, fn):
  _add("HAVE_FSTATAT", "stat")
  _add("HAVE_LCHFLAGS", "chflags")
  _add("HAVE_LCHMOD", "chmod")
+ _add("MS_WINDOWS", "chmod")
  if _exists("lchown"): # mac os x10.3
  _add("HAVE_LCHOWN", "chown")
  _add("HAVE_LINKAT", "link")

Lib/tempfile.py

@@ -273,7 +273,7 @@ def _dont_follow_symlinks(func, path, *args):
  # Pass follow_symlinks=False, unless not supported on this platform.
  if func in _os.supports_follow_symlinks:
  func(path, *args, follow_symlinks=False)
- elif _os.name == 'nt' or not _os.path.islink(path):
+ elif not _os.path.islink(path):
  func(path, *args)
 
 def _resetperms(path):

Lib/test/test_posix.py

@@ -1017,7 +1017,7 @@ def test_chmod_file_symlink(self):
  self.check_lchmod_link(posix.chmod, target, link)
  else:
  self.check_chmod_link(posix.chmod, target, link)
-self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
+ self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
 
  @os_helper.skip_unless_symlink
  def test_chmod_dir_symlink(self):
@@ -1029,7 +1029,7 @@ def test_chmod_dir_symlink(self):
  self.check_lchmod_link(posix.chmod, target, link)
  else:
  self.check_chmod_link(posix.chmod, target, link)
-self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
+ self.check_chmod_link(posix.chmod, target, link, follow_symlinks=True)
 
  @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
  @os_helper.skip_unless_symlink

Misc/NEWS.d/next/Library/2023-12-13-17-08-21.gh-issue-59616.JNlWSs.rst

@@ -0,0 +1,3 @@
+Add support of :func:`os.lchmod` and the *follow_symlinks* argument in
+:func:`os.chmod` on Windows. Note that the default value of *follow_symlinks*
+in :func:`!os.lchmod` is ``False`` on Windows.

Modules/posixmodule.c

@@ -3309,6 +3309,29 @@ os_fchdir_impl(PyObject *module, int fd)
 }
 #endif /* HAVE_FCHDIR */
 
+#ifdef MS_WINDOWS
+# define CHMOD_DEFAULT_FOLLOW_SYMLINKS 0
+#else
+# define CHMOD_DEFAULT_FOLLOW_SYMLINKS 1
+#endif
+
+#ifdef MS_WINDOWS
+static int
+win32_lchmod(LPCWSTR path, int mode)
+{
+ DWORD attr = GetFileAttributesW(path);
+ if (attr == INVALID_FILE_ATTRIBUTES) {
+ return 0;
+ }
+ if (mode & _S_IWRITE) {
+ attr &= ~FILE_ATTRIBUTE_READONLY;
+ }
+ else {
+ attr |= FILE_ATTRIBUTE_READONLY;
+ }
+ return SetFileAttributesW(path, attr);
+}
+#endif
 
 /*[clinic input]
 os.chmod
@@ -3331,7 +3354,8 @@ os.chmod
  and path should be relative; path will then be relative to that
  directory.
 
- follow_symlinks: bool = True
+ follow_symlinks: bool(c_default="CHMOD_DEFAULT_FOLLOW_SYMLINKS", \
+ py_default="(os.name != 'nt')") = CHMOD_DEFAULT_FOLLOW_SYMLINKS
  If False, and the last element of the path is a symbolic link,
  chmod will modify the symbolic link itself instead of the file
  the link points to.
@@ -3348,20 +3372,16 @@ dir_fd and follow_symlinks may not be implemented on your platform.
 static PyObject *
 os_chmod_impl(PyObject *module, path_t *path, int mode, int dir_fd,
  int follow_symlinks)
-/*[clinic end generated code: output=5cf6a94915cc7bff input=674a14bc998de09d]*/
+/*[clinic end generated code: output=5cf6a94915cc7bff input=fcf115d174b9f3d8]*/
 {
  int result;
 
-#ifdef MS_WINDOWS
- DWORD attr;
-#endif
-
 #ifdef HAVE_FCHMODAT
  int fchmodat_nofollow_unsupported = 0;
  int fchmodat_unsupported = 0;
 #endif
 
-#if !(defined(HAVE_FCHMODAT) || defined(HAVE_LCHMOD))
+#if !(defined(HAVE_FCHMODAT) || defined(HAVE_LCHMOD) || defined(MS_WINDOWS))
  if (follow_symlinks_specified("chmod", follow_symlinks))
  return NULL;
 #endif
@@ -3372,19 +3392,36 @@ os_chmod_impl(PyObject *module, path_t *path, int mode, int dir_fd,
  }
 
 #ifdef MS_WINDOWS
+ result = 0;
  Py_BEGIN_ALLOW_THREADS
- attr = GetFileAttributesW(path->wide);
- if (attr == INVALID_FILE_ATTRIBUTES)
- result = 0;
+ if (follow_symlinks) {
+ HANDLE hfile;
+ FILE_BASIC_INFO info;
+
+ hfile = CreateFileW(path->wide,
+ FILE_READ_ATTRIBUTES|FILE_WRITE_ATTRIBUTES,
+ 0, NULL,
+ OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+ if (hfile != INVALID_HANDLE_VALUE) {
+ if (GetFileInformationByHandleEx(hfile, FileBasicInfo,
+ &info, sizeof(info)))
+ {
+ if (mode & _S_IWRITE) {
+ info.FileAttributes &= ~FILE_ATTRIBUTE_READONLY;
+ }
+ else {
+ info.FileAttributes |= FILE_ATTRIBUTE_READONLY;
+ }
+ result = SetFileInformationByHandle(hfile, FileBasicInfo,
+ &info, sizeof(info));
+ }
+ (void)CloseHandle(hfile);
+ }
+ }
  else {
- if (mode & _S_IWRITE)
- attr &= ~FILE_ATTRIBUTE_READONLY;
- else
- attr |= FILE_ATTRIBUTE_READONLY;
- result = SetFileAttributesW(path->wide, attr);
+ result = win32_lchmod(path->wide, mode);
  }
  Py_END_ALLOW_THREADS
-
  if (!result) {
  return path_error(path);
  }
@@ -3514,7 +3551,7 @@ os_fchmod_impl(PyObject *module, int fd, int mode)
 #endif /* HAVE_FCHMOD */
 
 
-#ifdef HAVE_LCHMOD
+#if defined(HAVE_LCHMOD) || defined(MS_WINDOWS)
 /*[clinic input]
 os.lchmod
 
@@ -3535,16 +3572,26 @@ os_lchmod_impl(PyObject *module, path_t *path, int mode)
  if (PySys_Audit("os.chmod", "Oii", path->object, mode, -1) < 0) {
  return NULL;
  }
+#ifdef MS_WINDOWS
+ Py_BEGIN_ALLOW_THREADS
+ res = win32_lchmod(path->wide, mode);
+ Py_END_ALLOW_THREADS
+ if (!res) {
+ path_error(path);
+ return NULL;
+ }
+#else /* MS_WINDOWS */
  Py_BEGIN_ALLOW_THREADS
  res = lchmod(path->narrow, mode);
  Py_END_ALLOW_THREADS
  if (res < 0) {
  path_error(path);
  return NULL;
  }
+#endif /* MS_WINDOWS */
  Py_RETURN_NONE;
 }
-#endif /* HAVE_LCHMOD */
+#endif /* HAVE_LCHMOD || MS_WINDOWS */
 
 
 #ifdef HAVE_CHFLAGS

Tools/clinic/clinic.py

@@ -3737,7 +3737,7 @@ def converter_init(self, *, accept: TypeSet = {object}) -> None:
  self.format_unit = 'i'
  elif accept != {object}:
  fail(f"bool_converter: illegal 'accept' argument {accept!r}")
- if self.default is not unspecified:
+ if self.default is not unspecified and self.default is not unknown:
  self.default = bool(self.default)
  self.c_default = str(int(self.default))