Issue #18879: When a method is looked up on a temporary file, avoid closing the file before the method is possibly called.

This commit is contained in:
Antoine Pitrou 2013-12-21 22:14:56 +01:00
parent bdce938af2
commit 17c93260a6
3 changed files with 87 additions and 35 deletions

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@ -27,6 +27,7 @@ __all__ = [
# Imports.
import functools as _functools
import warnings as _warnings
import sys as _sys
import io as _io
@ -349,13 +350,10 @@ def mktemp(suffix="", prefix=template, dir=None):
"No usable temporary filename found")
class _TemporaryFileWrapper:
"""Temporary file wrapper
This class provides a wrapper around files opened for
temporary use. In particular, it seeks to automatically
remove the file when it is no longer needed.
"""
class _TemporaryFileCloser:
"""A separate object allowing proper closing of a temporary file's
underlying file object, without adding a __del__ method to the
temporary file."""
def __init__(self, file, name, delete=True):
self.file = file
@ -363,26 +361,6 @@ class _TemporaryFileWrapper:
self.close_called = False
self.delete = delete
def __getattr__(self, name):
# Attribute lookups are delegated to the underlying file
# and cached for non-numeric results
# (i.e. methods are cached, closed and friends are not)
file = self.__dict__['file']
a = getattr(file, name)
if not isinstance(a, int):
setattr(self, name, a)
return a
# The underlying __enter__ method returns the wrong object
# (self.file) so override it to return the wrapper
def __enter__(self):
self.file.__enter__()
return self
# iter() doesn't use __getattr__ to find the __iter__ method
def __iter__(self):
return iter(self.file)
# NT provides delete-on-close as a primitive, so we don't need
# the wrapper to do anything special. We still use it so that
# file.name is useful (i.e. not "(fdopen)") with NamedTemporaryFile.
@ -401,18 +379,72 @@ class _TemporaryFileWrapper:
if self.delete:
self.unlink(self.name)
# Need to ensure the file is deleted on __del__
def __del__(self):
self.close()
# Need to trap __exit__ as well to ensure the file gets
# deleted when used in a with statement
def __exit__(self, exc, value, tb):
result = self.file.__exit__(exc, value, tb)
self.close()
return result
else:
def __exit__(self, exc, value, tb):
self.file.__exit__(exc, value, tb)
def close(self):
if not self.close_called:
self.close_called = True
self.file.close()
class _TemporaryFileWrapper:
"""Temporary file wrapper
This class provides a wrapper around files opened for
temporary use. In particular, it seeks to automatically
remove the file when it is no longer needed.
"""
def __init__(self, file, name, delete=True):
self.file = file
self.name = name
self.delete = delete
self._closer = _TemporaryFileCloser(file, name, delete)
def __getattr__(self, name):
# Attribute lookups are delegated to the underlying file
# and cached for non-numeric results
# (i.e. methods are cached, closed and friends are not)
file = self.__dict__['file']
a = getattr(file, name)
if hasattr(a, '__call__'):
func = a
@_functools.wraps(func)
def func_wrapper(*args, **kwargs):
return func(*args, **kwargs)
# Avoid closing the file as long as the wrapper is alive,
# see issue #18879.
func_wrapper._closer = self._closer
a = func_wrapper
if not isinstance(a, int):
setattr(self, name, a)
return a
# The underlying __enter__ method returns the wrong object
# (self.file) so override it to return the wrapper
def __enter__(self):
self.file.__enter__()
return self
# Need to trap __exit__ as well to ensure the file gets
# deleted when used in a with statement
def __exit__(self, exc, value, tb):
result = self.file.__exit__(exc, value, tb)
self.close()
return result
def close(self):
"""
Close the temporary file, possibly deleting it.
"""
self._closer.close()
# iter() doesn't use __getattr__ to find the __iter__ method
def __iter__(self):
return iter(self.file)
def NamedTemporaryFile(mode='w+b', buffering=-1, encoding=None,

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@ -8,6 +8,7 @@ import sys
import re
import warnings
import contextlib
import weakref
import unittest
from test import support
@ -674,6 +675,22 @@ class TestNamedTemporaryFile(BaseTestCase):
self.do_create(pre="a", suf="b")
self.do_create(pre="aa", suf=".txt")
def test_method_lookup(self):
# Issue #18879: Looking up a temporary file method should keep it
# alive long enough.
f = self.do_create()
wr = weakref.ref(f)
write = f.write
write2 = f.write
del f
write(b'foo')
del write
write2(b'bar')
del write2
if support.check_impl_detail(cpython=True):
# No reference cycle was created.
self.assertIsNone(wr())
def test_creates_named(self):
# NamedTemporaryFile creates files with names
f = tempfile.NamedTemporaryFile()

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@ -29,6 +29,9 @@ Core and Builtins
Library
-------
- Issue #18879: When a method is looked up on a temporary file, avoid closing
the file before the method is possibly called.
- Issue #20034: Updated alias mapping to most recent locale.alias file
from X.org distribution using makelocalealias.py.