pytest: Internal error `py.error.EEXIST: [File exists]: mkdir(...)` on case insensitive file systems

real world case

Originally hit for these tests

I typically don’t develop on a mac, but noticed the tests failing there.

$ uname -a
Darwin Macbook-Pro 17.5.0 Darwin Kernel Version 17.5.0: Fri Apr 13 19:32:32 PDT 2018; root:xnu-4570.51.2~1/RELEASE_X86_64 x86_64 i386 MacBookPro11,4 Darwin

version

I’m running pytest 3.5.1, but have been able to reproduce this on every version back to 2.5.2 (at which I stopped trying because it can’t run python3.6!)

minimal reproduction

import pytest


@pytest.mark.parametrize('x', ('A', 'a'))
def test(x, tmpdir):
    pass

minimal reproduction output

$ .tox/py36/bin/pytest test.py
============================= test session starts ==============================
platform darwin -- Python 3.6.5, pytest-3.4.1, py-1.5.3, pluggy-0.6.0
rootdir: /private/tmp/yesqa, inifile:
collected 2 items                                                              

test.py .E                                                               [100%]

==================================== ERRORS ====================================
__________________________ ERROR at setup of test[a] ___________________________

self = <module 'py.error'>, func = <built-in function mkdir>
args = ('/private/var/folders/7x/97jnmnt13sl46bx2mc9chzpm0000gn/T/pytest-of-asottile/pytest-32/test_a_0',)
kwargs = {}, __tracebackhide__ = False, cls = <class 'py.error.EEXIST'>
value = FileExistsError(17, 'File exists')
tb = <traceback object at 0x1020f57c8>, errno = 17

    def checked_call(self, func, *args, **kwargs):
        """ call a function and raise an errno-exception if applicable. """
        __tracebackhide__ = True
        try:
>           return func(*args, **kwargs)
E           FileExistsError: [Errno 17] File exists: '/private/var/folders/7x/97jnmnt13sl46bx2mc9chzpm0000gn/T/pytest-of-asottile/pytest-32/test_a_0'

.tox/py36/lib/python3.6/site-packages/py/_error.py:66: FileExistsError

During handling of the above exception, another exception occurred:

self = <CallInfo when='setup' exception: [File exists]: mkdir('/private/var/folders/7x/97jnmnt13sl46bx2mc9chzpm0000gn/T/pytest-of-asottile/pytest-32/test_a_0',)>
func = <function call_runtest_hook.<locals>.<lambda> at 0x101f6e620>
when = 'setup'

    def __init__(self, func, when):
        #: context of invocation: one of "setup", "call",
        #: "teardown", "memocollect"
        self.when = when
        self.start = time()
        try:
>           self.result = func()

.tox/py36/lib/python3.6/site-packages/_pytest/runner.py:192: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
.tox/py36/lib/python3.6/site-packages/_pytest/runner.py:178: in <lambda>
    return CallInfo(lambda: ihook(item=item, **kwds), when=when)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:617: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:222: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:216: in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
.tox/py36/lib/python3.6/site-packages/_pytest/runner.py:103: in pytest_runtest_setup
    item.session._setupstate.prepare(item)
.tox/py36/lib/python3.6/site-packages/_pytest/runner.py:496: in prepare
    col.setup()
.tox/py36/lib/python3.6/site-packages/_pytest/python.py:1183: in setup
    fixtures.fillfixtures(self)
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:240: in fillfixtures
    request._fillfixtures()
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:382: in _fillfixtures
    item.funcargs[argname] = self.getfixturevalue(argname)
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:424: in getfixturevalue
    return self._get_active_fixturedef(argname).cached_result[0]
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:450: in _get_active_fixturedef
    self._compute_fixture_value(fixturedef)
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:521: in _compute_fixture_value
    fixturedef.execute(request=subrequest)
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:792: in execute
    return hook.pytest_fixture_setup(fixturedef=self, request=request)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:617: in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:222: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
.tox/py36/lib/python3.6/site-packages/pluggy/__init__.py:216: in <lambda>
    firstresult=hook.spec_opts.get('firstresult'),
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:823: in pytest_fixture_setup
    result = call_fixture_func(fixturefunc, request, kwargs)
.tox/py36/lib/python3.6/site-packages/_pytest/fixtures.py:715: in call_fixture_func
    res = fixturefunc(**kwargs)
.tox/py36/lib/python3.6/site-packages/_pytest/tmpdir.py:125: in tmpdir
    x = tmpdir_factory.mktemp(name, numbered=True)
.tox/py36/lib/python3.6/site-packages/_pytest/tmpdir.py:41: in mktemp
    keep=0, rootdir=basetemp, lock_timeout=None)
.tox/py36/lib/python3.6/site-packages/py/_path/local.py:863: in make_numbered_dir
    udir = rootdir.mkdir(prefix + str(maxnum+1))
.tox/py36/lib/python3.6/site-packages/py/_path/local.py:465: in mkdir
    py.error.checked_call(os.mkdir, fspath(p))
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <module 'py.error'>, func = <built-in function mkdir>
args = ('/private/var/folders/7x/97jnmnt13sl46bx2mc9chzpm0000gn/T/pytest-of-asottile/pytest-32/test_a_0',)
kwargs = {}, __tracebackhide__ = False, cls = <class 'py.error.EEXIST'>
value = FileExistsError(17, 'File exists')
tb = <traceback object at 0x1020f57c8>, errno = 17

    def checked_call(self, func, *args, **kwargs):
        """ call a function and raise an errno-exception if applicable. """
        __tracebackhide__ = True
        try:
            return func(*args, **kwargs)
        except self.Error:
            raise
        except (OSError, EnvironmentError):
            cls, value, tb = sys.exc_info()
            if not hasattr(value, 'errno'):
                raise
            __tracebackhide__ = False
            errno = value.errno
            try:
                if not isinstance(value, WindowsError):
                    raise NameError
            except NameError:
                # we are not on Windows, or we got a proper OSError
                cls = self._geterrnoclass(errno)
            else:
                try:
                    cls = self._geterrnoclass(_winerrnomap[errno])
                except KeyError:
                    raise value
>           raise cls("%s%r" % (func.__name__, args))
E           py.error.EEXIST: [File exists]: mkdir('/private/var/folders/7x/97jnmnt13sl46bx2mc9chzpm0000gn/T/pytest-of-asottile/pytest-32/test_a_0',)

.tox/py36/lib/python3.6/site-packages/py/_error.py:86: EEXIST
====================== 1 passed, 1 error in 0.31 seconds =======================