From 10b24e87e5e5f0ac421ab91fe993baf6b6e319c7 Mon Sep 17 00:00:00 2001
From: Amaury Forgeot d'Arc <amauryfa@gmail.com>
Date: Wed, 10 Dec 2008 23:49:33 +0000
Subject: Merged revisions 67688 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk
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........
  r67688 | amaury.forgeotdarc | 2008-12-11 00:22:49 +0100 (jeu., 11 déc. 2008) | 6 lines

  #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
........
---
 Lib/test/test_with.py | 30 ++++++++++++++++++++++++++++++
 Misc/NEWS             |  3 +++
 Python/ceval.c        | 13 +++++++++++--
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
index 43f3271..b192429 100644
--- a/Lib/test/test_with.py
+++ b/Lib/test/test_with.py
@@ -505,6 +505,36 @@ class ExceptionalTestCase(ContextmanagerAssertionMixin, unittest.TestCase):
 
         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 __bool__(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 cb2cf43..01a5927 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 3.1 alpha 0
 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 #4445: Replace "sizeof(PyBytesObject)" with
   "offsetof(PyBytesObject, ob_sval) + 1" when allocating memory for
   bytes instances.  On a typical machine this saves 3 bytes of memory
diff --git a/Python/ceval.c b/Python/ceval.c
index c394554..84d18b3 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2189,7 +2189,17 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 			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);
 				SET_TOP(PyLong_FromLong((long) WHY_SILENCED));
@@ -2197,7 +2207,6 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 				Py_DECREF(v);
 				Py_DECREF(w);
 			}
-			Py_DECREF(x);
 			PREDICT(END_FINALLY);
 			break;
 		}
-- 
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