django-admin runserver and get_child_arguments() crashes on Windows and Python < 3.8.

[andrey-zotov]

"django-admin runserver" fails with the following error:

Traceback (most recent call last):
  File "c:\users\someone\appdata\local\programs\python\python37\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\someone\AppData\Local\Programs\Python\Python37\Scripts\django-admin.exe\__main__.py", line 7, in <module>
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\commands\runserver.py", line 61, in execute
    super().execute(*args, **options)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\commands\runserver.py", line 96, in handle
    self.run(**options)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\core\management\commands\runserver.py", line 103, in run
    autoreload.run_with_reloader(self.inner_run, **options)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\utils\autoreload.py", line 616, in run_with_reloader
    exit_code = restart_with_reloader()
  File "c:\users\someone\appdata\local\programs\python\python37\lib\site-packages\django\utils\autoreload.py", line 244, in restart_with_reloader
    p = subprocess.run(args, env=new_environ, close_fds=False)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\subprocess.py", line 488, in run
    with Popen(*popenargs, **kwargs) as process:
  File "c:\users\someone\appdata\local\programs\python\python37\lib\subprocess.py", line 800, in __init__
    restore_signals, start_new_session)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\subprocess.py", line 1148, in _execute_child
    args = list2cmdline(args)
  File "c:\users\someone\appdata\local\programs\python\python37\lib\subprocess.py", line 555, in list2cmdline
    needquote = (" " in arg) or ("\t" in arg) or not arg
TypeError: argument of type 'WindowsPath' is not iterable

Environment:
Windows 10
Python: 3.7.6
Django: 3.1.3

Steps to reproduce:

django-admin startproject mysite
set PYTHONPATH=<thelocaldir>
django-admin runserver --settings=mysite.settings

Apparently django.utils.autoreload.get_child_arguments returns WindowsPath("C:\Users\someone\AppData\Local\Programs\Python\Python37\Scripts\django-admin.exe") as the first argument,
and subprocess.Popen expects a string and is not able to use Path.

The following monkey-patch fixes the error:

def get_child_arguments_override():
    args = autoreload._get_child_arguments()
    for i, arg in enumerate(args):
        if isinstance(arg, Path):
            args[i] = str(arg)
    return args

autoreload._get_child_arguments = autoreload.get_child_arguments
autoreload.get_child_arguments = get_child_arguments_override

[Mariusz Felisiak]

Tentatively accepted, I cannot check this on Windows, but it looks like a regression in 8a902b7ee622ada258d15fb122092c1f02b82698. subprocess.run()'s args parameter accepts path-like objects on Windows since Python 3.8 (see similar issue for dbshell, #31076).

[Carlton Gibson]

​PR

[GitHub <noreply@…>]

In ead37dfb:

Fixed #32202 -- Fixed autoreloader argument generation for Windows with Python 3.7-.

[Carlton Gibson <carlton.gibson@…>]

In 012822c7:

[3.1.x] Fixed #32202 -- Fixed autoreloader argument generation for Windows with Python 3.7-.

Backport of ead37dfb580136cc27dbd487a1f1ad90c9235d15 from master