gh-104803: Implement ntpath.isdevdrive for checking whether a path is on a Windows Dev Drive

Doc/library/os.path.rst

@@ -304,6 +304,24 @@ the :mod:`glob` module.)
  Accepts a :term:`path-like object`.
 
 
+.. function:: isdevdrive(path)
+
+ Return ``True`` if pathname *path* is located on a Windows Dev Drive.
+ A Dev Drive is optimized for developer scenarios, and offers faster
+ performance for reading and writing files. It is recommended for use for
+ source code, temporary build directories, package caches, and other
+ IO-intensive operations.
+
+ May raise an error for an invalid path, for example, one without a
+ recognizable drive, but returns ``False`` on platforms that do not support
+ Dev Drives. See `the Windows documentation <https://learn.microsoft.com/windows/dev-drive/>`_
+ for information on enabling and creating Dev Drives.
+
+ .. availability:: Windows.
+
+ .. versionadded:: 3.12
+
+
 .. function:: join(path, *paths)
 
  Join one or more path segments intelligently. The return value is the

Lib/ntpath.py

@@ -867,3 +867,19 @@ def commonpath(paths):
 except ImportError:
  # Use genericpath.* as imported above
  pass
+
+
+try:
+ from nt import _path_isdevdrive
+except ImportError:
+ def isdevdrive(path):
+ """Determines whether the specified path is on a Windows Dev Drive."""
+ # Never a Dev Drive
+ return False
+else:
+ def isdevdrive(path):
+ """Determines whether the specified path is on a Windows Dev Drive."""
+ try:
+ return _path_isdevdrive(abspath(path))
+ except OSError:
+ return False

Lib/test/test_ntpath.py

@@ -992,6 +992,26 @@ def test_fast_paths_in_use(self):
  self.assertTrue(os.path.exists is nt._path_exists)
  self.assertFalse(inspect.isfunction(os.path.exists))
 
+ @unittest.skipIf(os.name != 'nt', "Dev Drives only exist on Win32")
+ def test_isdevdrive(self):
+ # Result may be True or False, but shouldn't raise
+ self.assertIn(ntpath.isdevdrive(os_helper.TESTFN), (True, False))
+ # ntpath.isdevdrive can handle relative paths
+ self.assertIn(ntpath.isdevdrive("."), (True, False))
+ self.assertIn(ntpath.isdevdrive(b"."), (True, False))
+ # Volume syntax is supported
+ self.assertIn(ntpath.isdevdrive(os.listvolumes()[0]), (True, False))
+ # Invalid volume returns False from os.path method
+ self.assertFalse(ntpath.isdevdrive(r"\\?\Volume{00000000-0000-0000-0000-000000000000}\\"))
+ # Invalid volume raises from underlying helper
+ with self.assertRaises(OSError):
+ nt._path_isdevdrive(r"\\?\Volume{00000000-0000-0000-0000-000000000000}\\")
+
+ @unittest.skipIf(os.name == 'nt', "isdevdrive fallback only used off Win32")
+ def test_isdevdrive_fallback(self):
+ # Fallback always returns False
+ self.assertFalse(ntpath.isdevdrive(os_helper.TESTFN))
+
 
 class NtCommonTest(test_genericpath.CommonTest, unittest.TestCase):
  pathmodule = ntpath

Misc/NEWS.d/next/Windows/2023-05-23-19-26-28.gh-issue-104803.gqxYml.rst

@@ -0,0 +1,3 @@
+Add :func:`os.path.isdevdrive` to detect whether a path is on a Windows Dev
+Drive. Returns ``False`` on platforms that do not support Dev Drive, and is
+absent on non-Windows platforms.

Modules/posixmodule.c

@@ -4530,6 +4530,95 @@ os_listmounts_impl(PyObject *module, path_t *volume)
 }
 
 
+/*[clinic input]
+os._path_isdevdrive
+
+ path: path_t
+
+Determines whether the specified path is on a Windows Dev Drive.
+
+[clinic start generated code]*/
+
+static PyObject *
+os__path_isdevdrive_impl(PyObject *module, path_t *path)
+/*[clinic end generated code: output=1f437ea6677433a2 input=ee83e4996a48e23d]*/
+{
+#ifndef PERSISTENT_VOLUME_STATE_DEV_VOLUME
+ /* This flag will be documented at
+ https://learn.microsoft.com/windows-hardware/drivers/ddi/ntifs/ns-ntifs-_file_fs_persistent_volume_information
+ after release, and will be available in the latest WinSDK.
+ We include the flag to avoid a specific version dependency
+ on the latest WinSDK. */
+ const int PERSISTENT_VOLUME_STATE_DEV_VOLUME = 0x00002000;
+#endif
+ int err = 0;
+ PyObject *r = NULL;
+ wchar_t volume[MAX_PATH];
+
+ Py_BEGIN_ALLOW_THREADS
+ if (!GetVolumePathNameW(path->wide, volume, MAX_PATH)){
+ /* invalid path of some kind */
+ /* Note that this also includes the case where a volume is mounted
+ in a path longer than 260 characters. This is likely to be rare
+ and problematic for other reasons, so a (soft) failure in this
+ check seems okay. */
+ err = GetLastError();
+ } else if (GetDriveTypeW(volume) != DRIVE_FIXED){
+ /* only care about local dev drives */
+ r = Py_False;
+ } else{
+ HANDLE hVolume = CreateFileW(
+ volume,
+ FILE_READ_ATTRIBUTES,
+ FILE_SHARE_READ | FILE_SHARE_WRITE,
+ NULL,
+ OPEN_EXISTING,
+ FILE_FLAG_BACKUP_SEMANTICS,
+ NULL
+ );
+ if (hVolume == INVALID_HANDLE_VALUE){
+ err = GetLastError();
+ } else{
+ FILE_FS_PERSISTENT_VOLUME_INFORMATION volumeState ={0};
+ volumeState.Version = 1;
+ volumeState.FlagMask = PERSISTENT_VOLUME_STATE_DEV_VOLUME;
+ if (!DeviceIoControl(
+ hVolume,
+ FSCTL_QUERY_PERSISTENT_VOLUME_STATE,
+ &volumeState,
+ sizeof(volumeState),
+ &volumeState,
+ sizeof(volumeState),
+ NULL,
+ NULL
+ )){
+ err = GetLastError();
+ }
+ CloseHandle(hVolume);
+ if (err == ERROR_INVALID_PARAMETER){
+ /* not supported on this platform */
+ r = Py_False;
+ } else if (!err){
+ r = (volumeState.VolumeFlags & PERSISTENT_VOLUME_STATE_DEV_VOLUME)
+ ? Py_True : Py_False;
+ }
+ }
+ }
+ Py_END_ALLOW_THREADS
+
+ if (err){
+ PyErr_SetFromWindowsErr(err);
+ return NULL;
+ }
+
+ if (r){
+ return Py_NewRef(r);
+ }
+
+ return NULL;
+}
+
+
 int
 _PyOS_getfullpathname(const wchar_t *path, wchar_t **abspath_p)
 {
@@ -15797,6 +15886,7 @@ static PyMethodDef posix_methods[] ={
  OS_SETNS_METHODDEF
  OS_UNSHARE_METHODDEF
 
+ OS__PATH_ISDEVDRIVE_METHODDEF
  OS__PATH_ISDIR_METHODDEF
  OS__PATH_ISFILE_METHODDEF
  OS__PATH_ISLINK_METHODDEF