Issue #27123: When an exception is raised within the context being
managed by a contextlib.ExitStack() and one of the exit stack
generators catches and raises it in a chain, do not re-raise the
original exception when exiting, let the new chained one through.
This avoids the PEP 479 bug described in issue25782.
diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index 5377987..d44edd6 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -82,6 +82,9 @@
# raised inside the "with" statement from being suppressed.
return exc is not value
except RuntimeError as exc:
+ # Don't re-raise the passed in exception. (issue27112)
+ if exc is value:
+ return False
# Likewise, avoid suppressing if a StopIteration exception
# was passed to throw() and later wrapped into a RuntimeError
# (see PEP 479).
diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index 30a6377..a246c43 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -762,6 +762,34 @@
stack.push(cm)
self.assertIs(stack._exit_callbacks[-1], cm)
+ def test_dont_reraise_RuntimeError(self):
+ """https://bugs.python.org/issue27122"""
+ class UniqueException(Exception): pass
+
+ @contextmanager
+ def second():
+ try:
+ yield 1
+ except Exception as exc:
+ raise UniqueException("new exception") from exc
+
+ @contextmanager
+ def first():
+ try:
+ yield 1
+ except Exception as exc:
+ raise exc
+
+ # The RuntimeError should be caught by second()'s exception
+ # handler which chain raised a new UniqueException.
+ with self.assertRaises(UniqueException) as err_ctx:
+ with ExitStack() as es_ctx:
+ es_ctx.enter_context(second())
+ es_ctx.enter_context(first())
+ raise RuntimeError("please no infinite loop.")
+
+ self.assertEqual(err_ctx.exception.args[0], "new exception")
+
class TestRedirectStream: