bpo-29692: contextlib.contextmanager may incorrectly unchain RuntimeError (GH-949)
contextlib._GeneratorContextManager.__exit__ includes a special case to deal with
PEP 479 RuntimeErrors created when `StopIteration` is thrown into the context
manager body.
Previously this check was too permissive, and undid one level of chaining on *all*
RuntimeError instances, not just those that wrapped a StopIteration instance.
diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index e91cf46..5e47054 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -88,7 +88,7 @@
try:
next(self.gen)
except StopIteration:
- return
+ return False
else:
raise RuntimeError("generator didn't stop")
else:
@@ -110,7 +110,7 @@
# Likewise, avoid suppressing if a StopIteration exception
# was passed to throw() and later wrapped into a RuntimeError
# (see PEP 479).
- if exc.__cause__ is value:
+ if type is StopIteration and exc.__cause__ is value:
return False
raise
except:
@@ -121,10 +121,10 @@
# fixes the impedance mismatch between the throw() protocol
# and the __exit__() protocol.
#
- if sys.exc_info()[1] is not value:
- raise
- else:
- raise RuntimeError("generator didn't stop after throw()")
+ if sys.exc_info()[1] is value:
+ return False
+ raise
+ raise RuntimeError("generator didn't stop after throw()")
def contextmanager(func):