gh-119646: Include subprocess path in OSError on Windows (GH-157713)

Author: bmdhodl

Lib/subprocess.py

@@ -1629,21 +1629,31 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
             assert not pass_fds, "pass_fds not supported on Windows."
 
             if isinstance(args, str):
-                pass
+                # Filename is the program only. Later arguments can
+                # hold secrets. A leading quote ends at the next quote.
+                # Otherwise stop at the first space.
+                if args[:1] == '"':
+                    end = args.find('"', 1)
+                    orig_filename = args[1:end] if end != -1 else args
+                else:
+                    orig_filename = args.split(' ', 1)[0]
             elif isinstance(args, bytes):
                 if shell:
                     raise TypeError('bytes args is not allowed on Windows')
+                orig_filename = os.fsdecode(args)
                 args = list2cmdline([args])
             elif isinstance(args, os.PathLike):
                 if shell:
                     raise TypeError('path-like args is not allowed when '
                                     'shell is true')
+                orig_filename = os.fsdecode(args)
                 args = list2cmdline([args])
             else:
+                args = list(args)
+                orig_filename = os.fsdecode(args[0]) if args else None
                 args = list2cmdline(args)
-
             if executable is not None:
-                executable = os.fsdecode(executable)
+                orig_filename = executable = os.fsdecode(executable)
 
             # Process startup details
             if startupinfo is None:
@@ -1725,6 +1735,19 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
                                          env,
                                          cwd,
                                          startupinfo)
+            except OSError as e:
+                # gh-119646: POSIX already puts the attempted path on
+                # OSError.filename. Windows CreateProcess did not, so
+                # failures (missing exe, WSL paths, invalid cwd) were
+                # reported without naming the command.
+                if e.filename is None:
+                    # ERROR_DIRECTORY (267): CreateProcess rejected cwd.
+                    if cwd is not None and e.winerror == 267:
+                        name = cwd
+                    else:
+                        name = orig_filename
+                    raise type(e)(e.errno, e.strerror, name, e.winerror) from None
+                raise
             finally:
                 # Child is launched. Close the parent's copy of those pipe
                 # handles that only the child should have open.  You need

Lib/test/test_subprocess.py

@@ -1797,13 +1797,28 @@ def test_failed_child_execute_fd_leak(self):
         fds_after_exception = os.listdir(fd_directory)
         self.assertEqual(fds_before_popen, fds_after_exception)
 
-    @unittest.skipIf(mswindows, "behavior currently not supported on Windows")
     def test_file_not_found_includes_filename(self):
+        missing = (r'C:\opt\nonexistent_binary' if mswindows
+                   else '/opt/nonexistent_binary')
         with self.assertRaises(FileNotFoundError) as c:
-            subprocess.call(['/opt/nonexistent_binary', 'with', 'some', 'args'])
-        self.assertEqual(c.exception.filename, '/opt/nonexistent_binary')
+            subprocess.call([missing, 'with', 'some', 'args'])
+        self.assertEqual(c.exception.filename, missing)
+
+    def test_args_filter_iterable(self):
+        # gh-119646: Windows used to index args[0] before list2cmdline.
+        # test_faulthandler.test_sys_xoptions passes a filter() object.
+        args = filter(None, (sys.executable, "-c", "import sys; sys.exit(17)"))
+        self.assertEqual(subprocess.call(args), 17)
+
+    def test_file_not_found_includes_filename_from_iterable(self):
+        missing = (r'C:\opt\nonexistent_binary' if mswindows
+                   else '/opt/nonexistent_binary')
+        args = filter(None, (missing, "with", "some", "args"))
+        with self.assertRaises(FileNotFoundError) as c:
+            subprocess.call(args)
+        self.assertEqual(c.exception.filename, missing)
 
-    @unittest.skipIf(mswindows, "behavior currently not supported on Windows")
+    @unittest.skipIf(mswindows, "Windows reports NotADirectoryError (WinError 267)")
     def test_file_not_found_with_bad_cwd(self):
         with self.assertRaises(FileNotFoundError) as c:
             subprocess.Popen(['exit', '0'], cwd='/some/nonexistent/directory')
@@ -3718,6 +3733,34 @@ def test_vfork_used_when_expected(self):
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):
 
+    def test_createprocess_bad_cwd_includes_filename(self):
+        # gh-119646: invalid cwd should appear on OSError.filename.
+        missing_cwd = r'C:\some\nonexistent\directory'
+        with self.assertRaises(OSError) as c:
+            subprocess.Popen([sys.executable, '-c', 'pass'], cwd=missing_cwd)
+        self.assertEqual(c.exception.filename, missing_cwd)
+        self.assertEqual(c.exception.winerror, 267)
+
+    def test_command_string_filename_omits_later_args(self):
+        # gh-119646: a command-line string must not put later arguments
+        # on OSError.filename. Those arguments can hold secrets.
+        missing = r'C:\opt\nonexistent_binary'
+        secret = 'NOT-A-REAL-SECRET'
+        quoted = r'C:\Program Files\nonexistent_binary'
+        cases = [
+            (missing, missing),
+            (f'{missing} --token {secret}', missing),
+            (f'"{missing}" --token {secret}', missing),
+            (f'"{quoted}" --token {secret}', quoted),
+        ]
+        for command, expected in cases:
+            with self.subTest(command=command):
+                with self.assertRaises(FileNotFoundError) as c:
+                    subprocess.call(command)
+                self.assertEqual(c.exception.filename, expected)
+                self.assertNotIn(secret, c.exception.filename or '')
+                self.assertNotIn(secret, str(c.exception))
+
     def test_startupinfo(self):
         # startupinfo argument
         # We uses hardcoded constants, because we do not want to

Misc/NEWS.d/next/Library/2026-09-17-17-30-00.gh-issue-119646.kP8nQm.rst

@@ -0,0 +1,2 @@
+On Windows, :exc:`OSError` from :mod:`subprocess` now includes the attempted
+executable or working directory in ``filename``.