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Issue #27186: Update os.fspath()/PyOS_FSPath() to check the return 

type of __fspath__().

As part of this change, also make sure that the pure Python
implementation of os.fspath() is tested.
This commit is contained in:
Brett Cannon 2016-06-24 12:03:43 -07:00
parent 19b2a53a82
commit c78ca1e044
7 changed files with 101 additions and 71 deletions
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5
Doc/c-api/sys.rst
View File

@ -10,8 +10,9 @@ Operating System Utilities
Return the file system representation for *path*. If the object is a
:class:`str` or :class:`bytes` object, then its reference count is
incremented. If the object implements the :class:`os.PathLike` interface,
then ``type(path).__fspath__()`` is returned. Otherwise :exc:`TypeError` is
raised and ``NULL`` is returned.
then :meth:`~os.PathLike.__fspath__` is returned as long as it is a
:class:`str` or :class:`bytes` object. Otherwise :exc:`TypeError` is raised
and ``NULL`` is returned.
.. versionadded:: 3.6

14
Doc/library/os.rst
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@ -179,7 +179,8 @@ process and user.
.. versionadded:: 3.2
.. versionchanged:: 3.6
Support added to accept objects implementing :class:`os.PathLike`.
Support added to accept objects implementing the :class:`os.PathLike`
interface.
.. function:: fsdecode(filename)
@ -192,17 +193,18 @@ process and user.
.. versionadded:: 3.2
.. versionchanged:: 3.6
Support added to accept objects implementing :class:`os.PathLike`.
Support added to accept objects implementing the :class:`os.PathLike`
interface.
.. function:: fspath(path)
Return the file system representation of the path.
If :class:`str` or :class:`bytes` is passed in, it is returned unchanged;
otherwise, the result of calling ``type(path).__fspath__`` is returned
(which is represented by :class:`os.PathLike`). All other types raise a
:exc:`TypeError`.
If :class:`str` or :class:`bytes` is passed in, it is returned unchanged.
Otherwise :meth:`~os.PathLike.__fspath__` is called and its value is
returned as long as it is a :class:`str` or :class:`bytes` object.
In all other cases, :exc:`TypeError` is raised.
.. versionadded:: 3.6

73
Lib/os.py
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@ -881,14 +881,11 @@ def _fscodec():
On Windows, use 'strict' error handler if the file system encoding is
'mbcs' (which is the default encoding).
"""
filename = fspath(filename)
if isinstance(filename, bytes):
return filename
elif isinstance(filename, str):
filename = fspath(filename) # Does type-checking of `filename`.
if isinstance(filename, str):
return filename.encode(encoding, errors)
else:
raise TypeError("expected str, bytes or os.PathLike object, not "
+ type(filename).__name__)
return filename
def fsdecode(filename):
"""Decode filename (an os.PathLike, bytes, or str) from the filesystem
@ -896,14 +893,11 @@ def _fscodec():
Windows, use 'strict' error handler if the file system encoding is
'mbcs' (which is the default encoding).
"""
filename = fspath(filename)
if isinstance(filename, str):
return filename
elif isinstance(filename, bytes):
filename = fspath(filename) # Does type-checking of `filename`.
if isinstance(filename, bytes):
return filename.decode(encoding, errors)
else:
raise TypeError("expected str, bytes or os.PathLike object, not "
+ type(filename).__name__)
return filename
return fsencode, fsdecode
@ -1102,27 +1096,44 @@ def fdopen(fd, *args, **kwargs):
import io
return io.open(fd, *args, **kwargs)
# Supply os.fspath() if not defined in C
# For testing purposes, make sure the function is available when the C
# implementation exists.
def _fspath(path):
"""Return the path representation of a path-like object.
If str or bytes is passed in, it is returned unchanged. Otherwise the
os.PathLike interface is used to get the path representation. If the
path representation is not str or bytes, TypeError is raised. If the
provided path is not str, bytes, or os.PathLike, TypeError is raised.
"""
if isinstance(path, (str, bytes)):
return path
# Work from the object's type to match method resolution of other magic
# methods.
path_type = type(path)
try:
path_repr = path_type.__fspath__(path)
except AttributeError:
if hasattr(path_type, '__fspath__'):
raise
else:
raise TypeError("expected str, bytes or os.PathLike object, "
"not " + path_type.__name__)
if isinstance(path_repr, (str, bytes)):
return path_repr
else:
raise TypeError("expected {}.__fspath__() to return str or bytes, "
"not {}".format(path_type.__name__,
type(path_repr).__name__))
# If there is no C implementation, make the pure Python version the
# implementation as transparently as possible.
if not _exists('fspath'):
def fspath(path):
"""Return the string representation of the path.
fspath = _fspath
fspath.__name__ = "fspath"
If str or bytes is passed in, it is returned unchanged.
"""
if isinstance(path, (str, bytes)):
return path
# Work from the object's type to match method resolution of other magic
# methods.
path_type = type(path)
try:
return path_type.__fspath__(path)
except AttributeError:
if hasattr(path_type, '__fspath__'):
raise
raise TypeError("expected str, bytes or os.PathLike object, not "
+ path_type.__name__)
class PathLike(abc.ABC):

2
Lib/test/test_io.py
View File

@ -879,7 +879,7 @@ class IOTest(unittest.TestCase):
check_path_succeeds(PathLike(support.TESTFN.encode('utf-8')))
bad_path = PathLike(TypeError)
with self.assertRaisesRegex(TypeError, 'invalid file'):
with self.assertRaises(TypeError):
self.open(bad_path, 'w')
# ensure that refcounting is correct with some error conditions

62
Lib/test/test_os.py
View File

@ -3112,55 +3112,59 @@ class TestScandir(unittest.TestCase):
class TestPEP519(unittest.TestCase):
"os.fspath()"
# Abstracted so it can be overridden to test pure Python implementation
# if a C version is provided.
fspath = staticmethod(os.fspath)
class PathLike:
def __init__(self, path=''):
self.path = path
def __fspath__(self):
return self.path
def test_return_bytes(self):
for b in b'hello', b'goodbye', b'some/path/and/file':
self.assertEqual(b, os.fspath(b))
self.assertEqual(b, self.fspath(b))
def test_return_string(self):
for s in 'hello', 'goodbye', 'some/path/and/file':
self.assertEqual(s, os.fspath(s))
def test_fsencode_fsdecode_return_pathlike(self):
class PathLike:
def __init__(self, path):
self.path = path
def __fspath__(self):
return self.path
self.assertEqual(s, self.fspath(s))
def test_fsencode_fsdecode(self):
for p in "path/like/object", b"path/like/object":
pathlike = PathLike(p)
pathlike = self.PathLike(p)
self.assertEqual(p, os.fspath(pathlike))
self.assertEqual(p, self.fspath(pathlike))
self.assertEqual(b"path/like/object", os.fsencode(pathlike))
self.assertEqual("path/like/object", os.fsdecode(pathlike))
def test_fspathlike(self):
class PathLike:
def __init__(self, path=''):
self.path = path
def __fspath__(self):
return self.path
def test_pathlike(self):
self.assertEqual('#feelthegil', self.fspath(self.PathLike('#feelthegil')))
self.assertTrue(issubclass(self.PathLike, os.PathLike))
self.assertTrue(isinstance(self.PathLike(), os.PathLike))
self.assertEqual('#feelthegil', os.fspath(PathLike('#feelthegil')))
self.assertTrue(issubclass(PathLike, os.PathLike))
self.assertTrue(isinstance(PathLike(), os.PathLike))
message = 'expected str, bytes or os.PathLike object, not'
for fn in (os.fsencode, os.fsdecode):
for obj in PathLike(None), None:
with self.assertRaisesRegex(TypeError, message):
fn(obj)
with self.assertRaises(TypeError):
self.fspath(self.PathLike(42))
def test_garbage_in_exception_out(self):
vapor = type('blah', (), {})
for o in int, type, os, vapor():
self.assertRaises(TypeError, os.fspath, o)
self.assertRaises(TypeError, self.fspath, o)
def test_argument_required(self):
with self.assertRaises(TypeError):
os.fspath()
self.fspath()
# Only test if the C version is provided, otherwise TestPEP519 already tested
# the pure Python implementation.
if hasattr(os, "_fspath"):
class TestPEP519PurePython(TestPEP519):
"""Explicitly test the pure Python implementation of os.fspath()."""
fspath = staticmethod(os._fspath)
if __name__ == "__main__":

3
Misc/NEWS
View File

@ -10,6 +10,9 @@ What's New in Python 3.6.0 alpha 3
Library
-------
- Issue #27186: Update os.fspath()/PyOS_FSPath() to check the return value of
__fspath__() to be either str or bytes.
- Issue #18726: All optional parameters of the dump(), dumps(),
load() and loads() functions and JSONEncoder and JSONDecoder class
constructors in the json module are now keyword-only.

13
Modules/posixmodule.c
View File

@ -12317,12 +12317,21 @@ PyOS_FSPath(PyObject *path)
if (NULL == func) {
return PyErr_Format(PyExc_TypeError,
"expected str, bytes or os.PathLike object, "
"not %S",
path->ob_type);
"not %.200s",
Py_TYPE(path)->tp_name);
}
path_repr = PyObject_CallFunctionObjArgs(func, NULL);
Py_DECREF(func);
if (!(PyUnicode_Check(path_repr) || PyBytes_Check(path_repr))) {
PyErr_Format(PyExc_TypeError,
"expected %.200s.__fspath__() to return str or bytes, "
"not %.200s", Py_TYPE(path)->tp_name,
Py_TYPE(path_repr)->tp_name);
Py_DECREF(path_repr);
return NULL;
}
return path_repr;
}