bpo-39906: Add follow_symlinks parameter to pathlib.Path.stat() and chmod() (GH-18864)

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index 9db8ae2..eaaf980 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -393,8 +393,6 @@ class _NormalAccessor(_Accessor):
 
     stat = os.stat
 
-    lstat = os.lstat
-
     open = os.open
 
     listdir = os.listdir
@@ -403,12 +401,6 @@ class _NormalAccessor(_Accessor):
 
     chmod = os.chmod
 
-    if hasattr(os, "lchmod"):
-        lchmod = os.lchmod
-    else:
-        def lchmod(self, path, mode):
-            raise NotImplementedError("os.lchmod() not available on this system")
-
     mkdir = os.mkdir
 
     unlink = os.unlink
@@ -1191,12 +1183,12 @@ def resolve(self, strict=False):
         normed = self._flavour.pathmod.normpath(s)
         return self._from_parts((normed,))
 
-    def stat(self):
+    def stat(self, *, follow_symlinks=True):
         """
         Return the result of the stat() system call on this path, like
         os.stat() does.
         """
-        return self._accessor.stat(self)
+        return self._accessor.stat(self, follow_symlinks=follow_symlinks)
 
     def owner(self):
         """
@@ -1286,18 +1278,18 @@ def mkdir(self, mode=0o777, parents=False, exist_ok=False):
             if not exist_ok or not self.is_dir():
                 raise
 
-    def chmod(self, mode):
+    def chmod(self, mode, *, follow_symlinks=True):
         """
         Change the permissions of the path, like os.chmod().
         """
-        self._accessor.chmod(self, mode)
+        self._accessor.chmod(self, mode, follow_symlinks=follow_symlinks)
 
     def lchmod(self, mode):
         """
         Like chmod(), except if the path points to a symlink, the symlink's
         permissions are changed, rather than its target's.
         """
-        self._accessor.lchmod(self, mode)
+        self.chmod(mode, follow_symlinks=False)
 
     def unlink(self, missing_ok=False):
         """
@@ -1321,7 +1313,7 @@ def lstat(self):
         Like stat(), except if the path points to a symlink, the symlink's
         status information is returned, rather than its target's.
         """
-        return self._accessor.lstat(self)
+        return self.stat(follow_symlinks=False)
 
     def link_to(self, target):
         """
diff --git a/Lib/test/test_pathlib.py b/Lib/test/test_pathlib.py
index 9be7294..2643119 100644
--- a/Lib/test/test_pathlib.py
+++ b/Lib/test/test_pathlib.py
@@ -1828,6 +1828,21 @@ def test_chmod(self):
         p.chmod(new_mode)
         self.assertEqual(p.stat().st_mode, new_mode)
 
+    # On Windows, os.chmod does not follow symlinks (issue #15411)
+    @only_posix
+    def test_chmod_follow_symlinks_true(self):
+        p = self.cls(BASE) / 'linkA'
+        q = p.resolve()
+        mode = q.stat().st_mode
+        # Clear writable bit.
+        new_mode = mode & ~0o222
+        p.chmod(new_mode, follow_symlinks=True)
+        self.assertEqual(q.stat().st_mode, new_mode)
+        # Set writable bit
+        new_mode = mode | 0o222
+        p.chmod(new_mode, follow_symlinks=True)
+        self.assertEqual(q.stat().st_mode, new_mode)
+
     # XXX also need a test for lchmod.
 
     def test_stat(self):
@@ -1840,6 +1855,17 @@ def test_stat(self):
         self.assertNotEqual(p.stat(), st)
 
     @os_helper.skip_unless_symlink
+    def test_stat_no_follow_symlinks(self):
+        p = self.cls(BASE) / 'linkA'
+        st = p.stat()
+        self.assertNotEqual(st, p.stat(follow_symlinks=False))
+
+    def test_stat_no_follow_symlinks_nosymlink(self):
+        p = self.cls(BASE) / 'fileA'
+        st = p.stat()
+        self.assertEqual(st, p.stat(follow_symlinks=False))
+
+    @os_helper.skip_unless_symlink
     def test_lstat(self):
         p = self.cls(BASE)/ 'linkA'
         st = p.stat()