Implicit exception chaining via __context__ (PEP 3134).
Patch 3108 by Antooine Pitrou.
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 9068554..55a57ba 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -480,7 +480,12 @@
inner_raising_func()
except:
raise KeyError
- except KeyError:
+ except KeyError as e:
+ # We want to test that the except block above got rid of
+ # the exception raised in inner_raising_func(), but it
+ # also ends up in the __context__ of the KeyError, so we
+ # must clear the latter manually for our test to succeed.
+ e.__context__ = None
obj = None
obj = wr()
self.failUnless(obj is None, "%s" % obj)
diff --git a/Lib/test/test_raise.py b/Lib/test/test_raise.py
index 5f0070e..3072c14 100644
--- a/Lib/test/test_raise.py
+++ b/Lib/test/test_raise.py
@@ -181,32 +181,102 @@
self.fail("No exception raised")
-# Disabled until context is implemented
-# class TestContext(object):
-# def test_instance_context_bare_raise(self):
-# context = IndexError()
-# try:
-# try:
-# raise context
-# except:
-# raise OSError()
-# except OSError as e:
-# self.assertEqual(e.__context__, context)
-# else:
-# self.fail("No exception raised")
-#
-# def test_class_context_bare_raise(self):
-# context = IndexError
-# try:
-# try:
-# raise context
-# except:
-# raise OSError()
-# except OSError as e:
-# self.assertNotEqual(e.__context__, context)
-# self.failUnless(isinstance(e.__context__, context))
-# else:
-# self.fail("No exception raised")
+class TestContext(unittest.TestCase):
+ def test_instance_context_instance_raise(self):
+ context = IndexError()
+ try:
+ try:
+ raise context
+ except:
+ raise OSError()
+ except OSError as e:
+ self.assertEqual(e.__context__, context)
+ else:
+ self.fail("No exception raised")
+
+ def test_class_context_instance_raise(self):
+ context = IndexError
+ try:
+ try:
+ raise context
+ except:
+ raise OSError()
+ except OSError as e:
+ self.assertNotEqual(e.__context__, context)
+ self.failUnless(isinstance(e.__context__, context))
+ else:
+ self.fail("No exception raised")
+
+ def test_class_context_class_raise(self):
+ context = IndexError
+ try:
+ try:
+ raise context
+ except:
+ raise OSError
+ except OSError as e:
+ self.assertNotEqual(e.__context__, context)
+ self.failUnless(isinstance(e.__context__, context))
+ else:
+ self.fail("No exception raised")
+
+ def test_c_exception_context(self):
+ try:
+ try:
+ 1/0
+ except:
+ raise OSError
+ except OSError as e:
+ self.failUnless(isinstance(e.__context__, ZeroDivisionError))
+ else:
+ self.fail("No exception raised")
+
+ def test_c_exception_raise(self):
+ try:
+ try:
+ 1/0
+ except:
+ xyzzy
+ except NameError as e:
+ self.failUnless(isinstance(e.__context__, ZeroDivisionError))
+ else:
+ self.fail("No exception raised")
+
+ def test_noraise_finally(self):
+ try:
+ try:
+ pass
+ finally:
+ raise OSError
+ except OSError as e:
+ self.failUnless(e.__context__ is None)
+ else:
+ self.fail("No exception raised")
+
+ def test_raise_finally(self):
+ try:
+ try:
+ 1/0
+ finally:
+ raise OSError
+ except OSError as e:
+ self.failUnless(isinstance(e.__context__, ZeroDivisionError))
+ else:
+ self.fail("No exception raised")
+
+ def test_context_manager(self):
+ class ContextManager:
+ def __enter__(self):
+ pass
+ def __exit__(self, t, v, tb):
+ xyzzy
+ try:
+ with ContextManager():
+ 1/0
+ except NameError as e:
+ self.failUnless(isinstance(e.__context__, ZeroDivisionError))
+ else:
+ self.fail("No exception raised")
class TestRemovedFunctionality(unittest.TestCase):
diff --git a/Python/ceval.c b/Python/ceval.c
index bcb15e7..6aaa52d 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2817,11 +2817,12 @@
static enum why_code
do_raise(PyObject *exc, PyObject *cause)
{
- PyObject *type = NULL, *value = NULL, *tb = NULL;
+ PyObject *type = NULL, *value = NULL;
if (exc == NULL) {
/* Reraise */
PyThreadState *tstate = PyThreadState_GET();
+ PyObject *tb;
type = tstate->exc_type;
value = tstate->exc_value;
tb = tstate->exc_traceback;
@@ -2862,7 +2863,6 @@
goto raise_error;
}
- tb = PyException_GetTraceback(value);
if (cause) {
PyObject *fixed_cause;
if (PyExceptionClass_Check(cause)) {
@@ -2883,13 +2883,15 @@
PyException_SetCause(value, fixed_cause);
}
- PyErr_Restore(type, value, tb);
+ PyErr_SetObject(type, value);
+ /* PyErr_SetObject incref's its arguments */
+ Py_XDECREF(value);
+ Py_XDECREF(type);
return WHY_EXCEPTION;
raise_error:
Py_XDECREF(value);
Py_XDECREF(type);
- Py_XDECREF(tb);
Py_XDECREF(cause);
return WHY_EXCEPTION;
}
diff --git a/Python/errors.c b/Python/errors.c
index b765b03..ac64b6a 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -52,6 +52,9 @@
void
PyErr_SetObject(PyObject *exception, PyObject *value)
{
+ PyThreadState *tstate = PyThreadState_GET();
+ PyObject *tb = NULL;
+
if (exception != NULL &&
!PyExceptionClass_Check(exception)) {
PyErr_Format(PyExc_SystemError,
@@ -59,9 +62,35 @@
exception);
return;
}
- Py_XINCREF(exception);
Py_XINCREF(value);
- PyErr_Restore(exception, value, (PyObject *)NULL);
+ if (tstate->exc_value != NULL && tstate->exc_value != Py_None) {
+ /* Implicit exception chaining */
+ if (value == NULL || !PyExceptionInstance_Check(value)) {
+ /* We must normalize the value right now */
+ PyObject *args, *fixed_value;
+ if (value == NULL || value == Py_None)
+ args = PyTuple_New(0);
+ else if (PyTuple_Check(value)) {
+ Py_INCREF(value);
+ args = value;
+ }
+ else
+ args = PyTuple_Pack(1, value);
+ fixed_value = args ?
+ PyEval_CallObject(exception, args) : NULL;
+ Py_XDECREF(args);
+ Py_XDECREF(value);
+ if (fixed_value == NULL)
+ return;
+ value = fixed_value;
+ }
+ Py_INCREF(tstate->exc_value);
+ PyException_SetContext(value, tstate->exc_value);
+ }
+ if (value != NULL && PyExceptionInstance_Check(value))
+ tb = PyException_GetTraceback(value);
+ Py_XINCREF(exception);
+ PyErr_Restore(exception, value, tb);
}
void