[New-bugs-announce] [issue4589] 'with' loses ->bool exceptions
Jeffrey Yasskin
report at bugs.python.org
Mon Dec 8 07:21:10 CET 2008
New submission from Jeffrey Yasskin <jyasskin at gmail.com>:
When a context manager's __exit__() method returns an object whose
conversion to bool raises an exception, 'with' loses that exception. For
example:
>>> class CM(object):
... def __init__(self, exit_result):
... self.exit_result = exit_result
... def __enter__(self):
... return 3
... def __exit__(self, a, b, c):
... return self.exit_result()
...
>>> class TrueAsBool(object):
... def __nonzero__(self): return True
...
>>> class FalseAsBool(object):
... def __nonzero__(self): return False
...
>>> class FailAsBool(object):
... def __nonzero__(self):
... raise RuntimeError("Should see this but won't")
...
>>> with CM(TrueAsBool):
... raise AssertionError("Should NOT see this")
...
>>> with CM(FalseAsBool):
... raise AssertionError("Should see this")
...
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
AssertionError: Should see this
>>> with CM(FailAsBool):
... raise AssertionError("Should see RuntimeException (oops)")
...
>>>
The problem is that WITH_CLEANUP only checks if PyObject_IsTrue(x)
returns non-zero, but that function returns <0 when the bool conversion
raises an exception.
----------
assignee: jyasskin
components: Interpreter Core
messages: 77290
nosy: jyasskin
severity: normal
stage: needs patch
status: open
title: 'with' loses ->bool exceptions
type: behavior
versions: Python 2.5, Python 2.6, Python 2.7, Python 3.0, Python 3.1
_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue4589>
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