`pytest` uses filesystem root (`C:\`) as root dir on Windows

[bersbersbers]

My setup is a bit elaborate since I am using pyinstaller and running pytest from the bundled executable. Anyway, I can tell from the header that pytest is using C:\ as a rootdir and generates C:\.pytest_cache, which I would like to avoid.

By debugging determine_setup

pytest/src/_pytest/config/findpaths.py

Lines 175 to 218 in bc4e70e

	def determine_setup(
	inifile: Optional[str],
	args: Sequence[str],
	rootdir_cmd_arg: Optional[str] = None,
	config: Optional["Config"] = None,
	) -> Tuple[Path, Optional[Path], Dict[str, Union[str, List[str]]]]:
	rootdir = None
	dirs = get_dirs_from_args(args)
	if inifile:
	inipath_ = absolutepath(inifile)
	inipath: Optional[Path] = inipath_
	inicfg = load_config_dict_from_file(inipath_) or {}
	if rootdir_cmd_arg is None:
	rootdir = inipath_.parent
	else:
	ancestor = get_common_ancestor(dirs)
	rootdir, inipath, inicfg = locate_config([ancestor])
	if rootdir is None and rootdir_cmd_arg is None:
	for possible_rootdir in (ancestor, *ancestor.parents):
	if (possible_rootdir / "setup.py").is_file():
	rootdir = possible_rootdir
	break
	else:
	if dirs != [ancestor]:
	rootdir, inipath, inicfg = locate_config(dirs)
	if rootdir is None:
	if config is not None:
	cwd = config.invocation_params.dir
	else:
	cwd = Path.cwd()
	rootdir = get_common_ancestor([cwd, ancestor])
	is_fs_root = os.path.splitdrive(str(rootdir))[1] == "/"
	if is_fs_root:
	rootdir = ancestor
	if rootdir_cmd_arg:
	rootdir = absolutepath(os.path.expandvars(rootdir_cmd_arg))
	if not rootdir.is_dir():
	raise UsageError(
	"Directory '{}' not found. Check your '--rootdir' option.".format(
	rootdir
	)
	)
	assert rootdir is not None
	return rootdir, inipath, inicfg or {}

I have found that it is being called with the following parameters:

inifile = None
args = ['C:\\Users\\bers\\AppData\\Local\\Temp\\_MEI138802\\project']
rootdir_cmd_arg = None
rootdir = None
config = <_pytest.config.Config object at 0x0000021A33D60490>

I have no relevant config in the app bundle, so the function passes via

pytest/src/_pytest/config/findpaths.py

Lines 205 to 208 in bc4e70e

	rootdir = get_common_ancestor([cwd, ancestor])
	is_fs_root = os.path.splitdrive(str(rootdir))[1] == "/"
	if is_fs_root:
	rootdir = ancestor

with

cwd = WindowsPath('C:/Code/project')
ancestor = WindowsPath('C:/Users/bers/AppData/Local/Temp/_MEI138802/project')

rootdir = get_common_ancestor([cwd, ancestor]) returns WindowsPath('C:/'), but the following check returns false as os.path.splitdrive(str(rootdir))[1] is "\\", not "/". As a consequence, rootdir is not set to ancestor, but remains at WindowsPath('C:/'), which I believe is not intended.

TLDR: In

pytest/src/_pytest/config/findpaths.py

Line 206 in bc4e70e

is_fs_root = os.path.splitdrive(str(rootdir))[1] == "/"

change "/" to os.sep.