Close #14969: Improve the handling of exception chaining in contextlib.ExitStack
diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index f5232b6..bde2feb 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -225,6 +225,17 @@
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 @@
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 efa9dcb..e52ed91 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -505,6 +505,18 @@
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 @@
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 @@
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