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

Author: serhiy-storchaka

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/libregrtest/main.py

@@ -492,6 +492,7 @@ def _run_tests(self, selected: TestTuple, tests: TestList | None) -> int:
                                          self.fail_rerun)
 
     def run_tests(self, selected: TestTuple, tests: TestList | None) -> int:
+        selected = ('test_posix', 'test_tempfile')
         os.makedirs(self.tmp_dir, exist_ok=True)
         work_dir = get_work_dir(self.tmp_dir)
 

Lib/test/test_os.py

@@ -3117,6 +3117,56 @@ def test_directory_link_nonlocal(self):
         os.symlink('some_dir', src)
         assert os.path.isdir(src)
 
+    def test_chmod_link(self):
+        TESTFN2 = support.TESTFN+"_link"
+
+        def cleanup():
+            if os.path.exists(TESTFN2):
+                os.chmod(TESTFN2, 0o100666)
+                os.unlink(TESTFN2)
+
+            if os.path.exists(support.TESTFN):
+                os.chmod(support.TESTFN, 0o666)
+                os.unlink(support.TESTFN)
+
+        cleanup()
+
+        open(support.TESTFN, "w").close()
+        try:
+            os.symlink(support.TESTFN, TESTFN2)
+            os.chmod(TESTFN2, 0o444)
+            self.assertEqual(os.stat(TESTFN2).st_mode & 0o777, 0o444)
+
+            os.chmod(TESTFN2, 0o666)
+            self.assertEqual(os.stat(support.TESTFN).st_mode & 0o777, 0o666)
+        finally:
+            cleanup()
+
+    def test_chmod_link(self):
+        TESTFN2 = support.TESTFN+"_link"
+        
+        def cleanup():
+            if os.path.exists(TESTFN2):
+                os.chmod(TESTFN2, 0o100666)
+                os.unlink(TESTFN2)
+        
+            if os.path.exists(support.TESTFN):
+                os.chmod(support.TESTFN, 0o666)
+                os.unlink(support.TESTFN)
+                
+        cleanup()
+        
+        open(support.TESTFN, "w").close()
+        try:
+            os.symlink(support.TESTFN, TESTFN2) 
+            os.chmod(TESTFN2, 0o444)
+            self.assertEqual(os.stat(TESTFN2).st_mode & 0o777, 0o444)
+
+            os.chmod(TESTFN2, 0o666)
+            self.assertEqual(os.stat(support.TESTFN).st_mode & 0o777, 0o666)
+        finally:
+            cleanup()
+
 
 class FSEncodingTests(unittest.TestCase):
     def test_nop(self):

Lib/test/test_posix.py

@@ -21,8 +21,10 @@
 
 try:
     import posix
+    nt = None
 except ImportError:
-    import nt as posix
+    import nt
+    posix = nt
 
 try:
     import pwd
@@ -935,6 +937,116 @@ def test_utime(self):
         posix.utime(os_helper.TESTFN, (int(now), int(now)))
         posix.utime(os_helper.TESTFN, (now, now))
 
+    def check_chmod(self, chmod_func, target, **kwargs):
+        mode = os.stat(target).st_mode
+        try:
+            chmod_func(target, mode & ~stat.S_IWRITE, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, mode & ~stat.S_IWRITE)
+            if stat.S_ISREG(mode):
+                try:
+                    with open(target, 'wb+'):
+                        pass
+                except PermissionError:
+                    pass
+            chmod_func(target, mode | stat.S_IWRITE, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, mode | stat.S_IWRITE)
+            if stat.S_ISREG(mode):
+                with open(target, 'wb+'):
+                    pass
+        finally:
+            posix.chmod(target, mode)
+
+    def test_chmod_file(self):
+        self.check_chmod(posix.chmod, os_helper.TESTFN)
+
+    def tempdir(self):
+        target = os_helper.TESTFN + 'd'
+        posix.mkdir(target)
+        self.addCleanup(posix.rmdir, target)
+        return target
+
+    def test_chmod_dir(self):
+        target = self.tempdir()
+        self.check_chmod(posix.chmod, target)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    def test_lchmod_file(self):
+        self.check_chmod(posix.lchmod, os_helper.TESTFN)
+        self.check_chmod(posix.chmod, os_helper.TESTFN, follow_symlinks=False)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    def test_lchmod_dir(self):
+        target = self.tempdir()
+        self.check_chmod(posix.lchmod, target)
+        self.check_chmod(posix.chmod, target, follow_symlinks=False)
+
+    def check_chmod_link(self, chmod_func, target, link, **kwargs):
+        target_mode = os.stat(target).st_mode
+        link_mode = os.lstat(link).st_mode
+        try:
+            chmod_func(link, target_mode & ~stat.S_IWRITE, **kwargs)
+            self.assertEqual(os.stat(target).st_mode, target_mode & ~stat.S_IWRITE)
+            self.assertEqual(os.lstat(link).st_mode, link_mode)
+            chmod_func(link, target_mode | stat.S_IWRITE)
+            self.assertEqual(os.stat(target).st_mode, target_mode | stat.S_IWRITE)
+            self.assertEqual(os.lstat(link).st_mode, link_mode)
+        finally:
+            posix.chmod(target, target_mode)
+
+    def check_lchmod_link(self, chmod_func, target, link, **kwargs):
+        target_mode = os.stat(target).st_mode
+        link_mode = os.lstat(link).st_mode
+        chmod_func(link, link_mode & ~stat.S_IWRITE, **kwargs)
+        self.assertEqual(os.stat(target).st_mode, target_mode)
+        self.assertEqual(os.lstat(link).st_mode, link_mode & ~stat.S_IWRITE)
+        chmod_func(link, link_mode | stat.S_IWRITE)
+        self.assertEqual(os.stat(target).st_mode, target_mode)
+        self.assertEqual(os.lstat(link).st_mode, link_mode | stat.S_IWRITE)
+
+    @os_helper.skip_unless_symlink
+    def test_chmod_file_symlink(self):
+        target = os_helper.TESTFN
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        if os.name == 'nt':
+            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)
+
+    @os_helper.skip_unless_symlink
+    def test_chmod_dir_symlink(self):
+        target = self.tempdir()
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link, target_is_directory=True)
+        self.addCleanup(posix.unlink, link)
+        if os.name == 'nt':
+            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)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    @os_helper.skip_unless_symlink
+    def test_lchmod_file_symlink(self):
+        target = os_helper.TESTFN
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        self.check_lchmod_link(posix.chmod, target, link, follow_symlinks=False)
+        self.check_lchmod_link(posix.lchmod, target, link)
+
+    @unittest.skipUnless(hasattr(posix, 'lchmod'), 'test needs os.lchmod()')
+    @os_helper.skip_unless_symlink
+    def test_lchmod_dir_symlink(self):
+        target = self.tempdir()
+        link = os_helper.TESTFN + '-link'
+        os.symlink(target, link)
+        self.addCleanup(posix.unlink, link)
+        self.check_lchmod_link(posix.chmod, target, link, follow_symlinks=False)
+        self.check_lchmod_link(posix.lchmod, target, link)
+
     def _test_chflags_regular_file(self, chflags_func, target_file, **kwargs):
         st = os.stat(target_file)
         self.assertTrue(hasattr(st, 'st_flags'))