gh-104803: Implement ntpath.isdevdrive for checking whether a path is…

… on a Windows Dev Drive (GH-104805)

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

@@ -4534,6 +4534,95 @@ 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)
 {
@@ -15805,6 +15894,7 @@ 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