gh-158666: Avoid copy if shutil.move fails other than EXDEV

Lib/shutil.py

@@ -943,9 +943,10 @@ def move(src, dst, copy_function=copy2):
             raise Error("Destination path '%s' already exists" % real_dst)
     try:
         os.rename(src, real_dst)
-    except OSError:
+    except OSError as e:
         if os.path.islink(src):
             linkto = os.readlink(src)
+            _raise_not_exdev(e)
             os.symlink(linkto, real_dst)
             os.unlink(src)
         elif os.path.isdir(src):
@@ -958,10 +959,12 @@ def move(src, dst, copy_function=copy2):
                 raise PermissionError("Cannot move the non-empty directory "
                                       "'%s': Lacking write permission to '%s'."
                                       % (src, src))
+            _raise_not_exdev(e)
             copytree(src, real_dst, copy_function=copy_function,
                      symlinks=True)
             rmtree(src)
         else:
+            _raise_not_exdev(e)
             copy_function(src, real_dst)
             os.unlink(src)
     return real_dst
@@ -980,6 +983,10 @@ def _is_immutable(src):
     immutable_states = [stat.UF_IMMUTABLE, stat.SF_IMMUTABLE]
     return hasattr(st, 'st_flags') and st.st_flags in immutable_states
 
+def _raise_not_exdev(err):
+    if err.errno != errno.EXDEV:
+        raise err from None
+
 def _get_gid(name):
     """Returns a gid, given a group name."""
     if name is None:

Lib/test/test_shutil.py

@@ -3196,6 +3196,35 @@ def test_move_dir_permission_denied(self):
                 os.lchflags(TESTFN_DST, stat.UF_OPAQUE)
                 os_helper.rmtree(TESTFN_DST)
 
+    @unittest.mock.patch('os.rename')
+    def test_no_copied_file_left_not_EXDEV(self, mock_rename):
+        new_file = os.path.join(self.dst_dir, "bar")
+        mock_rename.side_effect = PermissionError("not EXDEV")
+        with self.assertRaises(PermissionError):
+            shutil.move(self.src_file, new_file)
+        self.assertFalse(os.path.exists(new_file))
+
+    @unittest.mock.patch('os.rename')
+    def test_no_copied_dir_left_not_EXDEV(self, mock_rename):
+        subdir = os.path.join(self.src_dir, "subdir")
+        os.mkdir(subdir)
+        new_dir = os.path.join(self.dst_dir, "new_dir")
+        mock_rename.side_effect = PermissionError("not EXDEV")
+        with self.assertRaises(PermissionError):
+            shutil.move(subdir, new_dir)
+        self.assertFalse(os.path.exists(new_dir))
+
+    @unittest.mock.patch('os.rename')
+    @os_helper.skip_unless_symlink
+    def test_no_copied_symlink_left_not_EXDEV(self, mock_rename):
+        old_link = os.path.join(self.src_dir, "bar")
+        os.symlink(os.path.basename(self.src_file), old_link)
+        new_link = os.path.join(self.dst_dir, "new_link")
+        mock_rename.side_effect = PermissionError("not EXDEV")
+        with self.assertRaises(PermissionError):
+            shutil.move(old_link, new_link)
+        self.assertFalse(os.path.exists(new_link))
+
 
 class TestCopyFile(unittest.TestCase):
 

Misc/NEWS.d/next/Library/2026-10-03-21-50-00.gh-issue-158666.D2POCj.rst

@@ -0,0 +1,2 @@
+:func:`shutil.move` won't copy the source to its destination if it fails
+with errors except EXDEV. Patch by Timothy Poon.