Implement ALL_BUT_LAST on Windows.

python · serhiy-storchaka · Jul 30, 2025 · Apr 5, 2024 · May 19, 2025 · May 19, 2025
commit b76a1c5f349ef56190e54ba97801914ee46d3b71
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
@@ -597,6 +597,9 @@ def abspath(path):
                 path = join(getcwd(), path)
         return normpath(path)
 
+# A singleton with true boolean value
+ALL_BUT_LAST = ['ALL_BUT_LAST']
+
 try:
     from nt import _findfirstfile, _getfinalpathname, readlink as _nt_readlink
 except ImportError:
@@ -735,7 +738,13 @@ def realpath(path, *, strict=False):
             path = normpath(path)
         except OSError as ex:
             if strict:
-                raise
+                if strict is not ALL_BUT_LAST or not isinstance(ex, FileNotFoundError):
+                    raise
+                dirname, basename = split(path)
+                if not basename:
+                    dirname, basename = split(path)
+                if not isdir(dirname):
+                    raise
             initial_winerror = ex.winerror
             path = _getfinalpathname_nonstrict(path)
         # The path returned by _getfinalpathname will always start with \\?\ -

diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
@@ -1,3 +1,4 @@
+import errno
 import inspect
 import ntpath
 import os
@@ -705,6 +706,132 @@ def test_realpath_permission(self):
 
         self.assertPathEqual(test_file, ntpath.realpath(test_file_short))
 
+    @os_helper.skip_unless_symlink
+    def test_realpath_mode(self):
+        realpath = ntpath.realpath
+        ALL_BUT_LAST = ntpath.ALL_BUT_LAST
+        ABSTFN = ntpath.abspath(os_helper.TESTFN)
+        try:
+            os.mkdir(ABSTFN)
+            os.mkdir(ABSTFN + "\\dir")
+            open(ABSTFN + "\\file", "wb").close()
+            open(ABSTFN + "\\dir\\file2", "wb").close()
+            os.symlink("file", ABSTFN + "\\link")
+            os.symlink("dir", ABSTFN + "\\link2")
+            os.symlink("nonexistent", ABSTFN + "\\broken")
+            os.symlink("cycle", ABSTFN + "\\cycle")
+            def check(path, mode, expected, errno=None):
+                path = path.replace('/', '\\')
+                if isinstance(expected, str):
+                    assert errno is None
+                    self.assertEqual(realpath(path, strict=mode), ABSTFN + expected.replace('/', '\\'))
+                else:
+                    with self.assertRaises(expected) as cm:
+                        realpath(path, strict=mode)
+                    if errno is not None:
+                        self.assertEqual(cm.exception.errno, errno)
+
+            with os_helper.change_cwd(ABSTFN):
+                check("file", False, "/file")
+                check("file", ALL_BUT_LAST, "/file")
+                check("file", True, "/file")
+                check("file/", False, "/file")
+                # check("file/", ALL_BUT_LAST, NotADirectoryError)
+                # check("file/", True, NotADirectoryError)
+                check("file/file2", False, "/file/file2")
+                # check("file/file2", ALL_BUT_LAST, NotADirectoryError)
+                # check("file/file2", True, NotADirectoryError)
+                check("file/.", False, "/file")
+                # check("file/.", ALL_BUT_LAST, NotADirectoryError)
+                # check("file/.", True, NotADirectoryError)
+                check("file/../link2", False, "/dir")
+                check("file/../link2", ALL_BUT_LAST, "/dir")
+                check("file/../link2", True, "/dir")
+
+                check("dir", False, "/dir")
+                check("dir", ALL_BUT_LAST, "/dir")
+                check("dir", True, "/dir")
+                check("dir/", False, "/dir")
+                check("dir/", ALL_BUT_LAST, "/dir")
+                check("dir/", True, "/dir")
+                check("dir/file2", False, "/dir/file2")
+                check("dir/file2", ALL_BUT_LAST, "/dir/file2")
+                check("dir/file2", True, "/dir/file2")
+
+                check("link", False, "/file")
+                check("link", ALL_BUT_LAST, "/file")
+                check("link", True, "/file")
+                check("link/", False, "/file")
+                # check("link/", ALL_BUT_LAST, NotADirectoryError)
+                # check("link/", True, NotADirectoryError)
+                check("link/file2", False, "/file/file2")
+                # check("link/file2", ALL_BUT_LAST, NotADirectoryError)
+                # check("link/file2", True, NotADirectoryError)
+                check("link/.", False, "/file")
+                # check("link/.", ALL_BUT_LAST, NotADirectoryError)
+                # check("link/.", True, NotADirectoryError)
+                check("link/../link", False, "/file")
+                check("link/../link", ALL_BUT_LAST, "/file")
+                check("link/../link", True, "/file")
+
+                check("link2", False, "/dir")
+                check("link2", ALL_BUT_LAST, "/dir")
+                check("link2", True, "/dir")
+                check("link2/", False, "/dir")
+                check("link2/", ALL_BUT_LAST, "/dir")
+                check("link2/", True, "/dir")
+                check("link2/file2", False, "/dir/file2")
+                check("link2/file2", ALL_BUT_LAST, "/dir/file2")
+                check("link2/file2", True, "/dir/file2")
+
+                check("nonexistent", False, "/nonexistent")
+                check("nonexistent", ALL_BUT_LAST, "/nonexistent")
+                check("nonexistent", True, FileNotFoundError)
+                check("nonexistent/", False, "/nonexistent")
+                check("nonexistent/", ALL_BUT_LAST, "/nonexistent")
+                check("nonexistent/", True, FileNotFoundError)
+                check("nonexistent/file", False, "/nonexistent/file")
+                check("nonexistent/file", ALL_BUT_LAST, FileNotFoundError)
+                check("nonexistent/file", True, FileNotFoundError)
+                check("nonexistent/../link", False, "/file")
+                check("nonexistent/../link", ALL_BUT_LAST, "/file")
+                check("nonexistent/../link", True, "/file")
+
+                check("broken", False, "/nonexistent")
+                check("broken", ALL_BUT_LAST, "/nonexistent")
+                check("broken", True, FileNotFoundError)
+                check("broken/", False, "/nonexistent")
+                check("broken/", ALL_BUT_LAST, "/nonexistent")
+                check("broken/", True, FileNotFoundError)
+                check("broken/file", False, "/nonexistent/file")
+                check("broken/file", ALL_BUT_LAST, FileNotFoundError)
+                check("broken/file", True, FileNotFoundError)
+                check("broken/../link", False, "/file")
+                check("broken/../link", ALL_BUT_LAST, "/file")
+                check("broken/../link", True, "/file")
+
+                check("cycle", False, "/cycle")
+                check("cycle", ALL_BUT_LAST, OSError, errno.EINVAL)
+                check("cycle", True, OSError, errno.EINVAL)
+                check("cycle/", False, "/cycle")
+                check("cycle/", ALL_BUT_LAST, OSError, errno.EINVAL)
+                check("cycle/", True, OSError, errno.EINVAL)
+                check("cycle/file", False, "/cycle/file")
+                check("cycle/file", ALL_BUT_LAST, OSError, errno.EINVAL)
+                check("cycle/file", True, OSError, errno.EINVAL)
+                check("cycle/../link", False, "/file")
+                check("cycle/../link", ALL_BUT_LAST, "/file")
+                check("cycle/../link", True, "/file")
+        finally:
+            os_helper.unlink(ABSTFN + "/file")
+            os_helper.unlink(ABSTFN + "/dir/file2")
+            os_helper.unlink(ABSTFN + "/link")
+            os_helper.unlink(ABSTFN + "/link2")
+            os_helper.unlink(ABSTFN + "/broken")
+            os_helper.unlink(ABSTFN + "/cycle")
+            os_helper.rmdir(ABSTFN + "/dir")
+            os_helper.rmdir(ABSTFN)
+
     def test_expandvars(self):
         with os_helper.EnvironmentVarGuard() as env:
             env.clear()

diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
@@ -767,7 +767,7 @@ def test_realpath_nonterminal_symlink_to_symlinks_to_file(self):
             os_helper.unlink(ABSTFN)
 
     @os_helper.skip_unless_symlink
-    @skip_if_ABSTFN_contains_backslash
+    # @skip_if_ABSTFN_contains_backslash
     def test_realpath_mode(self):
         try:
             os.mkdir(ABSTFN)
@@ -781,7 +781,8 @@ def test_realpath_mode(self):
             def check(path, mode, expected, errno=None):
                 if isinstance(expected, str):
                     assert errno is None
-                    self.assertEqual(realpath(path, strict=mode), ABSTFN + expected)
+                    self.assertEqual(realpath(path, strict=mode).replace('/', os.sep),
+                                     ABSTFN.replace('/', os.sep) + expected.replace('/', os.sep))
                 else:
                     with self.assertRaises(expected) as cm:
                         realpath(path, strict=mode)