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Issue 20317: Remove debugging code from contextlib

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- Alex J Burke noticed a debugging raise in the commit that
  fixed the original bug reported in issue 20317
- this showed that multiple iterations through the affected
  loop wasn't actually being tested
This commit is contained in:
Nick Coghlan 2014-01-24 23:05:45 +10:00
parent 5f6bf55965
commit add94c9d82
2 changed files with 49 additions and 13 deletions
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4
Lib/contextlib.py
View File

@ -231,7 +231,7 @@ class ExitStack(object):
# we were actually nesting multiple with statements
frame_exc = sys.exc_info()[1]
def _fix_exception_context(new_exc, old_exc):
# Context isn't what we want, so find the end of the chain
# Context may not be correct, so find the end of the chain
while 1:
exc_context = new_exc.__context__
if exc_context is old_exc:
@ -239,8 +239,6 @@ class ExitStack(object):
return
if exc_context is None or exc_context is frame_exc:
break
details = id(new_exc), id(old_exc), id(exc_context)
raise Exception(str(details))
new_exc = exc_context
# Change the end of the chain to point to the exception
# we expect it to reference

58
Lib/test/test_contextlib.py
View File

@ -603,24 +603,62 @@ class TestExitStack(unittest.TestCase):
def test_exit_exception_with_correct_context(self):
# http://bugs.python.org/issue20317
@contextmanager
def gets_the_context_right():
def gets_the_context_right(exc):
try:
yield 6
yield
finally:
1 / 0
raise exc
exc1 = Exception(1)
exc2 = Exception(2)
exc3 = Exception(3)
exc4 = Exception(4)
# The contextmanager already fixes the context, so prior to the
# fix, ExitStack would try to fix it *again* and get into an
# infinite self-referential loop
try:
with ExitStack() as stack:
stack.enter_context(gets_the_context_right())
stack.enter_context(gets_the_context_right())
stack.enter_context(gets_the_context_right())
except ZeroDivisionError as exc:
self.assertIsInstance(exc.__context__, ZeroDivisionError)
self.assertIsInstance(exc.__context__.__context__, ZeroDivisionError)
self.assertIsNone(exc.__context__.__context__.__context__)
stack.enter_context(gets_the_context_right(exc4))
stack.enter_context(gets_the_context_right(exc3))
stack.enter_context(gets_the_context_right(exc2))
raise exc1
except Exception as exc:
self.assertIs(exc, exc4)
self.assertIs(exc.__context__, exc3)
self.assertIs(exc.__context__.__context__, exc2)
self.assertIs(exc.__context__.__context__.__context__, exc1)
self.assertIsNone(
exc.__context__.__context__.__context__.__context__)
def test_exit_exception_with_existing_context(self):
# Addresses a lack of test coverage discovered after checking in a
# fix for issue 20317 that still contained debugging code.
def raise_nested(inner_exc, outer_exc):
try:
raise inner_exc
finally:
raise outer_exc
exc1 = Exception(1)
exc2 = Exception(2)
exc3 = Exception(3)
exc4 = Exception(4)
exc5 = Exception(5)
try:
with ExitStack() as stack:
stack.callback(raise_nested, exc4, exc5)
stack.callback(raise_nested, exc2, exc3)
raise exc1
except Exception as exc:
self.assertIs(exc, exc5)
self.assertIs(exc.__context__, exc4)
self.assertIs(exc.__context__.__context__, exc3)
self.assertIs(exc.__context__.__context__.__context__, exc2)
self.assertIs(
exc.__context__.__context__.__context__.__context__, exc1)
self.assertIsNone(
exc.__context__.__context__.__context__.__context__.__context__)
def test_body_exception_suppress(self):