gh-156210: Fix shutil.copytree() detection of dangling relative symlinks

Author: lpyu001

Lib/shutil.py

@@ -593,7 +593,7 @@ def _copytree(entries, src, dst, symlinks, ignore, copy_function,
                     copystat(srcobj, dstname, follow_symlinks=not symlinks)
                 else:
                     # ignore dangling symlink if the flag is on
-                    if not os.path.exists(linkto) and ignore_dangling_symlinks:
+                    if not os.path.exists(srcname) and ignore_dangling_symlinks:
                         continue
                     # otherwise let the copy occur. copy2 will raise an error
                     if srcentry.is_dir():

Lib/test/test_shutil.py

@@ -1060,6 +1060,35 @@ def test_copytree_dangling_symlinks(self):
         shutil.copytree(src_dir, dst_dir, symlinks=True)
         self.assertIn('test.txt', os.listdir(dst_dir))
 
+    @os_helper.skip_unless_symlink
+    def test_copytree_valid_relative_symlink(self):
+        root_dir = self.mkdtemp()
+        src_dir = os.path.join(root_dir, 'source')
+        os.mkdir(src_dir)
+        create_file(os.path.join(src_dir, 'target'), 'abc')
+        os.symlink('target', os.path.join(src_dir, 'link'))
+
+        dst_dir = os.path.join(root_dir, 'destination')
+        with os_helper.change_cwd(root_dir):
+            shutil.copytree(src_dir, dst_dir, ignore_dangling_symlinks=True)
+        self.assertEqual(['link', 'target'], sorted(os.listdir(dst_dir)))
+        self.assertFalse(os.path.islink(os.path.join(dst_dir, 'link')))
+        self.assertEqual('abc', read_file(os.path.join(dst_dir, 'link')))
+
+    @os_helper.skip_unless_symlink
+    def test_copytree_dangling_relative_symlink(self):
+        root_dir = self.mkdtemp()
+        src_dir = os.path.join(root_dir, 'source')
+        os.mkdir(src_dir)
+        os.symlink('target', os.path.join(src_dir, 'link'))
+        create_file(os.path.join(root_dir, 'target'), 'abc')
+
+        dst_dir = os.path.join(root_dir, 'destination')
+        with os_helper.change_cwd(root_dir):
+            shutil.copytree(src_dir, dst_dir,
+                            ignore_dangling_symlinks=True)
+        self.assertEqual([], os.listdir(dst_dir))
+
     @os_helper.skip_unless_symlink
     def test_copytree_symlink_dir(self):
         src_dir = self.mkdtemp()

Misc/NEWS.d/next/Library/2026-08-22-11-00-09.gh-issue-156210.IBtBw-.rst

@@ -0,0 +1,3 @@
+Fix :func:`shutil.copytree` to determine whether relative symbolic links are
+dangling based on their parent directory rather than the current working
+directory when ``ignore_dangling_symlinks`` is true.