Close issue #6210: Implement PEP 409

1 files changed, 18 insertions, 11 deletions

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index e9522e8..bc43799 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -266,28 +266,35 @@ BaseException_get_cause(PyObject *self) {
     PyObject *res = PyException_GetCause(self);
     if (res)
         return res;  /* new reference already returned above */
-    Py_RETURN_NONE;
+    Py_INCREF(Py_Ellipsis);
+    return Py_Ellipsis;
 }
 
-static int
-BaseException_set_cause(PyObject *self, PyObject *arg) {
-    if (arg == NULL) {
-        PyErr_SetString(PyExc_TypeError, "__cause__ may not be deleted");
-        return -1;
-    } else if (arg == Py_None) {
+int
+_PyException_SetCauseChecked(PyObject *self, PyObject *arg) {
+    if (arg == Py_Ellipsis) {
         arg = NULL;
-    } else if (!PyExceptionInstance_Check(arg)) {
-        PyErr_SetString(PyExc_TypeError, "exception cause must be None "
-                        "or derive from BaseException");
+    } else if (arg != Py_None && !PyExceptionInstance_Check(arg)) {
+        PyErr_SetString(PyExc_TypeError, "exception cause must be None, "
+                        "Ellipsis or derive from BaseException");
         return -1;
     } else {
-        /* PyException_SetCause steals this reference */
+        /* PyException_SetCause steals a reference */
         Py_INCREF(arg);
     }
     PyException_SetCause(self, arg);
     return 0;
 }
 
+static int
+BaseException_set_cause(PyObject *self, PyObject *arg) {
+    if (arg == NULL) {
+        PyErr_SetString(PyExc_TypeError, "__cause__ may not be deleted");
+        return -1;
+    }
+    return _PyException_SetCauseChecked(self, arg);
+}
+
 
 static PyGetSetDef BaseException_getset[] = {
     {"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict},