bpo-40851: Don't set wShowWindow if startupinfo has STARTF_USESHOWWINDOW

Author: ZackerySpytz

Lib/subprocess.py

@@ -1401,8 +1401,9 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
                     close_fds = False
 
             if shell:
-                startupinfo.dwFlags |= _winapi.STARTF_USESHOWWINDOW
-                startupinfo.wShowWindow = _winapi.SW_HIDE
+                if not startupinfo.dwFlags & _winapi.STARTF_USESHOWWINDOW:
+                    startupinfo.dwFlags |= _winapi.STARTF_USESHOWWINDOW
+                    startupinfo.wShowWindow = _winapi.SW_HIDE
                 comspec = os.environ.get("COMSPEC", "cmd.exe")
                 args = '{} /c "{}"'.format (comspec, args)