diff --git a/Lib/contextlib.py b/Lib/contextlib.py index f5232b6a842..bde2feb68e3 100644 --- a/Lib/contextlib.py +++ b/Lib/contextlib.py @@ -225,6 +225,17 @@ class ExitStack(object): return self def __exit__(self, *exc_details): + # We manipulate the exception state so it behaves as though + # we were actually nesting multiple with statements + frame_exc = sys.exc_info()[1] + def _fix_exception_context(new_exc, old_exc): + while 1: + exc_context = new_exc.__context__ + if exc_context in (None, frame_exc): + break + new_exc = exc_context + new_exc.__context__ = old_exc + # Callbacks are invoked in LIFO order to match the behaviour of # nested context managers suppressed_exc = False @@ -236,9 +247,8 @@ class ExitStack(object): exc_details = (None, None, None) except: new_exc_details = sys.exc_info() - if exc_details != (None, None, None): - # simulate the stack of exceptions by setting the context - new_exc_details[1].__context__ = exc_details[1] + # simulate the stack of exceptions by setting the context + _fix_exception_context(new_exc_details[1], exc_details[1]) if not self._exit_callbacks: raise exc_details = new_exc_details diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py index efa9dcbc36f..e52ed91a585 100644 --- a/Lib/test/test_contextlib.py +++ b/Lib/test/test_contextlib.py @@ -505,6 +505,18 @@ class TestExitStack(unittest.TestCase): def __exit__(self, *exc_details): raise self.exc + class RaiseExcWithContext: + def __init__(self, outer, inner): + self.outer = outer + self.inner = inner + def __enter__(self): + return self + def __exit__(self, *exc_details): + try: + raise self.inner + except: + raise self.outer + class SuppressExc: def __enter__(self): return self @@ -514,11 +526,10 @@ class TestExitStack(unittest.TestCase): try: with RaiseExc(IndexError): - with RaiseExc(KeyError): - with RaiseExc(AttributeError): - with SuppressExc(): - with RaiseExc(ValueError): - 1 / 0 + with RaiseExcWithContext(KeyError, AttributeError): + with SuppressExc(): + with RaiseExc(ValueError): + 1 / 0 except IndexError as exc: self.assertIsInstance(exc.__context__, KeyError) self.assertIsInstance(exc.__context__.__context__, AttributeError) @@ -553,12 +564,8 @@ class TestExitStack(unittest.TestCase): except IndexError as exc: self.assertIsInstance(exc.__context__, KeyError) self.assertIsInstance(exc.__context__.__context__, AttributeError) - # Inner exceptions were suppressed, but the with statement - # cleanup code adds the one from the body back in as the - # context of the exception raised by the outer callbacks - # See http://bugs.python.org/issue14969 - suite_exc = exc.__context__.__context__.__context__ - self.assertIsInstance(suite_exc, ZeroDivisionError) + # Inner exceptions were suppressed + self.assertIsNone(exc.__context__.__context__.__context__) else: self.fail("Expected IndexError, but no exception was raised") # Check the inner exceptions diff --git a/Misc/NEWS b/Misc/NEWS index 7dcf4b55423..7c5a86f7fae 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -10,6 +10,8 @@ What's New in Python 3.3.0 Beta 1? Library ------- +- Issue #14969: Better handling of exception chaining in contextlib.ExitStack + - Issue #14962: Update text coloring in IDLE shell window after changing options. Patch by Roger Serwy.