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Close #14963: Use an iterative algorithm in contextlib.ExitStack.__exit__ (Patch by Alon Horev)

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This commit is contained in:
Nick Coghlan 2012-06-01 00:00:38 +10:00
parent c73e8c2830
commit a5bd2a18ce
3 changed files with 29 additions and 28 deletions
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43
Lib/contextlib.py
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@ -225,32 +225,21 @@ class ExitStack(object):
return self
def __exit__(self, *exc_details):
if not self._exit_callbacks:
return
# This looks complicated, but it is really just
# setting up a chain of try-expect statements to ensure
# that outer callbacks still get invoked even if an
# inner one throws an exception
def _invoke_next_callback(exc_details):
# Callbacks are removed from the list in FIFO order
# but the recursion means they're invoked in LIFO order
cb = self._exit_callbacks.popleft()
if not self._exit_callbacks:
# Innermost callback is invoked directly
return cb(*exc_details)
# More callbacks left, so descend another level in the stack
# Callbacks are invoked in LIFO order to match the behaviour of
# nested context managers
suppressed_exc = False
while self._exit_callbacks:
cb = self._exit_callbacks.pop()
try:
suppress_exc = _invoke_next_callback(exc_details)
except:
suppress_exc = cb(*sys.exc_info())
# Check if this cb suppressed the inner exception
if not suppress_exc:
raise
else:
# Check if inner cb suppressed the original exception
if suppress_exc:
if cb(*exc_details):
suppressed_exc = True
exc_details = (None, None, None)
suppress_exc = cb(*exc_details) or suppress_exc
return suppress_exc
# Kick off the recursive chain
return _invoke_next_callback(exc_details)
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]
if not self._exit_callbacks:
raise
exc_details = new_exc_details
return suppressed_exc