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Issue #22854: Clarify documentation about UnsupportedOperation and add tests 

Also change BufferedReader.writable() and BufferedWriter.readable() to always
return False.
This commit is contained in:
Martin Panter 2016-03-31 07:21:56 +00:00
parent 8dc2ec1513
commit 754aab28ed
6 changed files with 130 additions and 35 deletions
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18
Lib/_pyio.py
View File

@ -390,7 +390,7 @@ class IOBase(metaclass=abc.ABCMeta):
def seekable(self):
"""Return a bool indicating whether object supports random access.
If False, seek(), tell() and truncate() will raise UnsupportedOperation.
If False, seek(), tell() and truncate() will raise OSError.
This method may need to do a test seek().
"""
return False
@ -405,7 +405,7 @@ class IOBase(metaclass=abc.ABCMeta):
def readable(self):
"""Return a bool indicating whether object was opened for reading.
If False, read() will raise UnsupportedOperation.
If False, read() will raise OSError.
"""
return False
@ -419,7 +419,7 @@ class IOBase(metaclass=abc.ABCMeta):
def writable(self):
"""Return a bool indicating whether object was opened for writing.
If False, write() and truncate() will raise UnsupportedOperation.
If False, write() and truncate() will raise OSError.
"""
return False
@ -787,12 +787,6 @@ class _BufferedIOMixin(BufferedIOBase):
def seekable(self):
return self.raw.seekable()
def readable(self):
return self.raw.readable()
def writable(self):
return self.raw.writable()
@property
def raw(self):
return self._raw
@ -982,6 +976,9 @@ class BufferedReader(_BufferedIOMixin):
self._reset_read_buf()
self._read_lock = Lock()
def readable(self):
return self.raw.readable()
def _reset_read_buf(self):
self._read_buf = b""
self._read_pos = 0
@ -1170,6 +1167,9 @@ class BufferedWriter(_BufferedIOMixin):
self._write_buf = bytearray()
self._write_lock = Lock()
def writable(self):
return self.raw.writable()
def write(self, b):
if self.closed:
raise ValueError("write to closed file")

116
Lib/test/test_io.py
View File

@ -203,6 +203,9 @@ class MockUnseekableIO:
def tell(self, *args):
raise self.UnsupportedOperation("not seekable")
def truncate(self, *args):
raise self.UnsupportedOperation("not seekable")
class CMockUnseekableIO(MockUnseekableIO, io.BytesIO):
UnsupportedOperation = io.UnsupportedOperation
@ -361,6 +364,107 @@ class IOTest(unittest.TestCase):
self.assertRaises(exc, fp.seek, 1, self.SEEK_CUR)
self.assertRaises(exc, fp.seek, -1, self.SEEK_END)
def test_optional_abilities(self):
# Test for OSError when optional APIs are not supported
# The purpose of this test is to try fileno(), reading, writing and
# seeking operations with various objects that indicate they do not
# support these operations.
def pipe_reader():
[r, w] = os.pipe()
os.close(w) # So that read() is harmless
return self.FileIO(r, "r")
def pipe_writer():
[r, w] = os.pipe()
self.addCleanup(os.close, r)
# Guarantee that we can write into the pipe without blocking
thread = threading.Thread(target=os.read, args=(r, 100))
thread.start()
self.addCleanup(thread.join)
return self.FileIO(w, "w")
def buffered_reader():
return self.BufferedReader(self.MockUnseekableIO())
def buffered_writer():
return self.BufferedWriter(self.MockUnseekableIO())
def buffered_random():
return self.BufferedRandom(self.BytesIO())
def buffered_rw_pair():
return self.BufferedRWPair(self.MockUnseekableIO(),
self.MockUnseekableIO())
def text_reader():
class UnseekableReader(self.MockUnseekableIO):
writable = self.BufferedIOBase.writable
write = self.BufferedIOBase.write
return self.TextIOWrapper(UnseekableReader(), "ascii")
def text_writer():
class UnseekableWriter(self.MockUnseekableIO):
readable = self.BufferedIOBase.readable
read = self.BufferedIOBase.read
return self.TextIOWrapper(UnseekableWriter(), "ascii")
tests = (
(pipe_reader, "fr"), (pipe_writer, "fw"),
(buffered_reader, "r"), (buffered_writer, "w"),
(buffered_random, "rws"), (buffered_rw_pair, "rw"),
(text_reader, "r"), (text_writer, "w"),
(self.BytesIO, "rws"), (self.StringIO, "rws"),
)
for [test, abilities] in tests:
if test is pipe_writer and not threading:
continue # Skip subtest that uses a background thread
with self.subTest(test), test() as obj:
readable = "r" in abilities
self.assertEqual(obj.readable(), readable)
writable = "w" in abilities
self.assertEqual(obj.writable(), writable)
seekable = "s" in abilities
self.assertEqual(obj.seekable(), seekable)
if isinstance(obj, self.TextIOBase):
data = "3"
elif isinstance(obj, (self.BufferedIOBase, self.RawIOBase)):
data = b"3"
else:
self.fail("Unknown base class")
if "f" in abilities:
obj.fileno()
else:
self.assertRaises(OSError, obj.fileno)
if readable:
obj.read(1)
obj.read()
else:
self.assertRaises(OSError, obj.read, 1)
self.assertRaises(OSError, obj.read)
if writable:
obj.write(data)
else:
self.assertRaises(OSError, obj.write, data)
if seekable:
obj.tell()
obj.seek(0)
else:
self.assertRaises(OSError, obj.tell)
self.assertRaises(OSError, obj.seek, 0)
if writable and seekable:
obj.truncate()
obj.truncate(0)
else:
self.assertRaises(OSError, obj.truncate)
self.assertRaises(OSError, obj.truncate, 0)
def test_open_handles_NUL_chars(self):
fn_with_NUL = 'foo\0bar'
self.assertRaises(ValueError, self.open, fn_with_NUL, 'w')
@ -747,12 +851,6 @@ class CommonBufferedTests:
self.assertEqual(42, bufio.fileno())
@unittest.skip('test having existential crisis')
def test_no_fileno(self):
# XXX will we always have fileno() function? If so, kill
# this test. Else, write it.
pass
def test_invalid_args(self):
rawio = self.MockRawIO()
bufio = self.tp(rawio)
@ -780,13 +878,9 @@ class CommonBufferedTests:
super().flush()
rawio = self.MockRawIO()
bufio = MyBufferedIO(rawio)
writable = bufio.writable()
del bufio
support.gc_collect()
if writable:
self.assertEqual(record, [1, 2, 3])
else:
self.assertEqual(record, [1, 2])
self.assertEqual(record, [1, 2, 3])
def test_context_manager(self):
# Test usability as a context manager

3
Misc/NEWS
View File

@ -99,6 +99,9 @@ Core and Builtins
Library
-------
- Issue #22854: Change BufferedReader.writable() and
BufferedWriter.readable() to always return False.
- Issue #25195: Fix a regression in mock.MagicMock. _Call is a subclass of
tuple (changeset 3603bae63c13 only works for classes) so we need to
implement __ne__ ourselves. Patch by Andrew Plummer.

2
Modules/_io/bufferedio.c
View File

@ -2398,7 +2398,6 @@ static PyMethodDef bufferedreader_methods[] = {
{"close", (PyCFunction)buffered_close, METH_NOARGS},
{"seekable", (PyCFunction)buffered_seekable, METH_NOARGS},
{"readable", (PyCFunction)buffered_readable, METH_NOARGS},
{"writable", (PyCFunction)buffered_writable, METH_NOARGS},
{"fileno", (PyCFunction)buffered_fileno, METH_NOARGS},
{"isatty", (PyCFunction)buffered_isatty, METH_NOARGS},
{"_dealloc_warn", (PyCFunction)buffered_dealloc_warn, METH_O},
@ -2489,7 +2488,6 @@ static PyMethodDef bufferedwriter_methods[] = {
{"close", (PyCFunction)buffered_close, METH_NOARGS},
{"detach", (PyCFunction)buffered_detach, METH_NOARGS},
{"seekable", (PyCFunction)buffered_seekable, METH_NOARGS},
{"readable", (PyCFunction)buffered_readable, METH_NOARGS},
{"writable", (PyCFunction)buffered_writable, METH_NOARGS},
{"fileno", (PyCFunction)buffered_fileno, METH_NOARGS},
{"isatty", (PyCFunction)buffered_isatty, METH_NOARGS},

10
Modules/_io/clinic/iobase.c.h
View File

@ -66,7 +66,7 @@ PyDoc_STRVAR(_io__IOBase_seekable__doc__,
"\n"
"Return whether object supports random access.\n"
"\n"
"If False, seek(), tell() and truncate() will raise UnsupportedOperation.\n"
"If False, seek(), tell() and truncate() will raise OSError.\n"
"This method may need to do a test seek().");
#define _IO__IOBASE_SEEKABLE_METHODDEF \
@ -87,7 +87,7 @@ PyDoc_STRVAR(_io__IOBase_readable__doc__,
"\n"
"Return whether object was opened for reading.\n"
"\n"
"If False, read() will raise UnsupportedOperation.");
"If False, read() will raise OSError.");
#define _IO__IOBASE_READABLE_METHODDEF \
{"readable", (PyCFunction)_io__IOBase_readable, METH_NOARGS, _io__IOBase_readable__doc__},
@ -107,7 +107,7 @@ PyDoc_STRVAR(_io__IOBase_writable__doc__,
"\n"
"Return whether object was opened for writing.\n"
"\n"
"If False, write() will raise UnsupportedOperation.");
"If False, write() will raise OSError.");
#define _IO__IOBASE_WRITABLE_METHODDEF \
{"writable", (PyCFunction)_io__IOBase_writable, METH_NOARGS, _io__IOBase_writable__doc__},
@ -127,7 +127,7 @@ PyDoc_STRVAR(_io__IOBase_fileno__doc__,
"\n"
"Returns underlying file descriptor if one exists.\n"
"\n"
"An IOError is raised if the IO object does not use a file descriptor.");
"OSError is raised if the IO object does not use a file descriptor.");
#define _IO__IOBASE_FILENO_METHODDEF \
{"fileno", (PyCFunction)_io__IOBase_fileno, METH_NOARGS, _io__IOBase_fileno__doc__},
@ -276,4 +276,4 @@ _io__RawIOBase_readall(PyObject *self, PyObject *Py_UNUSED(ignored))
{
return _io__RawIOBase_readall_impl(self);
}
/*[clinic end generated code: output=fe034152b6884e65 input=a9049054013a1b77]*/
/*[clinic end generated code: output=b874952f5cc248a4 input=a9049054013a1b77]*/

16
Modules/_io/iobase.c
View File

@ -335,13 +335,13 @@ _io._IOBase.seekable
Return whether object supports random access.
If False, seek(), tell() and truncate() will raise UnsupportedOperation.
If False, seek(), tell() and truncate() will raise OSError.
This method may need to do a test seek().
[clinic start generated code]*/
static PyObject *
_io__IOBase_seekable_impl(PyObject *self)
/*[clinic end generated code: output=4c24c67f5f32a43d input=22676eebb81dcf1e]*/
/*[clinic end generated code: output=4c24c67f5f32a43d input=b976622f7fdf3063]*/
{
Py_RETURN_FALSE;
}
@ -368,12 +368,12 @@ _io._IOBase.readable
Return whether object was opened for reading.
If False, read() will raise UnsupportedOperation.
If False, read() will raise OSError.
[clinic start generated code]*/
static PyObject *
_io__IOBase_readable_impl(PyObject *self)
/*[clinic end generated code: output=e48089250686388b input=12fc3d8f6be46434]*/
/*[clinic end generated code: output=e48089250686388b input=285b3b866a0ec35f]*/
{
Py_RETURN_FALSE;
}
@ -401,12 +401,12 @@ _io._IOBase.writable
Return whether object was opened for writing.
If False, write() will raise UnsupportedOperation.
If False, write() will raise OSError.
[clinic start generated code]*/
static PyObject *
_io__IOBase_writable_impl(PyObject *self)
/*[clinic end generated code: output=406001d0985be14f input=c17a0bb6a8dfc590]*/
/*[clinic end generated code: output=406001d0985be14f input=9dcac18a013a05b5]*/
{
Py_RETURN_FALSE;
}
@ -456,12 +456,12 @@ _io._IOBase.fileno
Returns underlying file descriptor if one exists.
An IOError is raised if the IO object does not use a file descriptor.
OSError is raised if the IO object does not use a file descriptor.
[clinic start generated code]*/
static PyObject *
_io__IOBase_fileno_impl(PyObject *self)
/*[clinic end generated code: output=7cc0973f0f5f3b73 input=32773c5df4b7eede]*/
/*[clinic end generated code: output=7cc0973f0f5f3b73 input=4e37028947dc1cc8]*/
{
return iobase_unsupported("fileno");
}