#4559: When a context manager's __exit__() method returns an object whose
conversion to bool raises an exception, 'with' loses that exception.
Reviewed by Jeffrey Yasskin.
Already ported to 2.5, will port to 2.6 and 3.0
diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
index 3007e5a..bfeb06b 100644
--- a/Lib/test/test_with.py
+++ b/Lib/test/test_with.py
@@ -503,6 +503,36 @@
self.assertRaises(GeneratorExit, shouldThrow)
+ def testErrorsInBool(self):
+ # issue4589: __exit__ return code may raise an exception
+ # when looking at its truth value.
+
+ class cm(object):
+ def __init__(self, bool_conversion):
+ class Bool:
+ def __nonzero__(self):
+ return bool_conversion()
+ self.exit_result = Bool()
+ def __enter__(self):
+ return 3
+ def __exit__(self, a, b, c):
+ return self.exit_result
+
+ def trueAsBool():
+ with cm(lambda: True):
+ self.fail("Should NOT see this")
+ trueAsBool()
+
+ def falseAsBool():
+ with cm(lambda: False):
+ self.fail("Should raise")
+ self.assertRaises(AssertionError, falseAsBool)
+
+ def failAsBool():
+ with cm(lambda: 1//0):
+ self.fail("Should NOT see this")
+ self.assertRaises(ZeroDivisionError, failAsBool)
+
class NonLocalFlowControlTestCase(unittest.TestCase):
diff --git a/Misc/NEWS b/Misc/NEWS
index 8a86d7c..e964ced 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and Builtins
-----------------
+- Issue #4597: Fixed exception handling when the __exit__ function of a
+ context manager returns a value that cannot be converted to a bool.
+
- Issue #4597: Fixed several opcodes that weren't always propagating
exceptions.
diff --git a/Python/ceval.c b/Python/ceval.c
index 0a1d86a..bd35185 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2349,11 +2349,20 @@
/* XXX Not the fastest way to call it... */
x = PyObject_CallFunctionObjArgs(exit_func, u, v, w,
NULL);
- if (x == NULL) {
- Py_DECREF(exit_func);
+ Py_DECREF(exit_func);
+ if (x == NULL)
break; /* Go to error exit */
- }
- if (u != Py_None && PyObject_IsTrue(x)) {
+
+ if (u != Py_None)
+ err = PyObject_IsTrue(x);
+ else
+ err = 0;
+ Py_DECREF(x);
+
+ if (err < 0)
+ break; /* Go to error exit */
+ else if (err > 0) {
+ err = 0;
/* There was an exception and a true return */
STACKADJ(-2);
Py_INCREF(Py_None);
@@ -2365,8 +2374,6 @@
/* The stack was rearranged to remove EXIT
above. Let END_FINALLY do its thing */
}
- Py_DECREF(x);
- Py_DECREF(exit_func);
PREDICT(END_FINALLY);
break;
}