Merged revisions 67688 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  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

@@ -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):
 

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

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;
 		}