No such file or directory in the fake filesystem: b'/tmp'

[Wenzel]

Describe the bug

pyfakefs complains that /tmp directory does not exists, despite the docs stating that "This means that any newly created fake file system will always have either a directory named /tmp when running on Linux or Unix systems"

How To Reproduce
Please have a look at this small repo:
https://github.com/Wenzel/bug_pyfakefs

smply run python -m pytest -v to reproduce the bug:

venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:4624: in open
    return fake_open(file, mode, buffering, encoding, errors,
venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:5202: in __call__
    return self.call(*args, **kwargs)
venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:5263: in call
    file_object = self._init_file_object(file_object,
venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:5330: in _init_file_object
    file_object = self.filesystem.create_file_internally(
venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:2608: in create_file_internally
    self.raise_os_error(errno.ENOENT, parent_directory)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pyfakefs.fake_filesystem.FakeFilesystem object at 0x7f94c2304ac0>, errno = 2, filename = b'/tmp', winerror = None

    def raise_os_error(self, errno, filename=None, winerror=None):
        """Raises OSError.
        The error message is constructed from the given error code and shall
        start with the error string issued in the real system.
        Note: this is not true under Windows if winerror is given - in this
        case a localized message specific to winerror will be shown in the
        real file system.

        Args:
            errno: A numeric error code from the C variable errno.
            filename: The name of the affected file, if any.
            winerror: Windows only - the specific Windows error code.
        """
        message = self._error_message(errno)
        if (winerror is not None and sys.platform == 'win32' and
                self.is_windows_fs):
            raise OSError(errno, message, filename, winerror)
>       raise OSError(errno, message, filename)
E       FileNotFoundError: [Errno 2] No such file or directory in the fake filesystem: b'/tmp'

venv/lib/python3.8/site-packages/pyfakefs/fake_filesystem.py:1010: FileNotFoundError
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Going up in the stacktrace:

We see here that an error is raised because /tmp is not found.

Your environment
Please run the following and paste the output.

Linux-5.4.0-73-generic-x86_64-with-glibc2.29
Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
[GCC 9.3.0]
pyfakefs 4.4.0

Thanks for your help !

[mrbean-bremen]

Thanks for the report!
Out of the box I have no idea. Just to be sure - can you please check what import tempfile; print(tempfile.gettempdir()) returns on your system? This is the path that shall be created in the fake filesystem at startup.

[Wenzel]

I've just updated the test to print the tempdir returned by gettempdir() and check if it exists:
https://github.com/Wenzel/bug_pyfakefs/blob/master/tests/test_01.py#L10

The result is that it exists before and after the yield:

tests/test_01.py::test_create_container_ok fixture: tmp dir before yield: /tmp - exists:  True
PASSEDfixture: tmp dir after yield: /tmp - exists:  True

tests/test_01.py::test_create_container_ok ERROR

So I don't understand what's going on here

[Wenzel]

Okay, I've just found something:

When you pass the filepath as str, it works, but when you pass it as bytes, it fails:

I hopes this can shed some lights

[Wenzel]

The problem comes from exists() which cannot handle a bytes filepath:

>>> self.exists(b'/tmp')
False
>>> self.exists('/tmp')
True
>>> 

[mrbean-bremen]

Ah, thank you - that is helpful! Handling of str vs bytes is something that I have addressed in most places (hopefully), but obviously not all. I will have a look somewhere in the next days, thanks!

[mrbean-bremen]

@Wenzel - shall be fixed now in master, please check!

[Wenzel]

@mrbean-bremen thank you for the quick fix, I confirmed the issue is solved !
Thank you very much for the support.

[mrbean-bremen]

Thanks - you are welcome!