Issue #28289: ImportError.__init__ now resets not specified attributes.

Lib/test/test_exceptions.py

@@ -1112,6 +1112,20 @@ class ImportErrorTests(unittest.TestCase):
         with self.assertRaisesRegex(TypeError, msg):
             ImportError('test', invalid='keyword', another=True)
 
+    def test_reset_attributes(self):
+        exc = ImportError('test', name='name', path='path')
+        self.assertEqual(exc.args, ('test',))
+        self.assertEqual(exc.msg, 'test')
+        self.assertEqual(exc.name, 'name')
+        self.assertEqual(exc.path, 'path')
+
+        # Reset not specified attributes
+        exc.__init__()
+        self.assertEqual(exc.args, ())
+        self.assertEqual(exc.msg, None)
+        self.assertEqual(exc.name, None)
+        self.assertEqual(exc.path, None)
+
     def test_non_str_argument(self):
         # Issue #15778
         with check_warnings(('', BytesWarning), quiet=True):

Misc/NEWS

@@ -10,6 +10,8 @@ What's New in Python 3.7.0 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #28289: ImportError.__init__ now resets not specified attributes.
+
 - Issue #21578: Fixed misleading error message when ImportError called with
   invalid keyword args.
 

Objects/exceptions.c

@@ -631,19 +631,17 @@ ImportError_init(PyImportErrorObject *self, PyObject *args, PyObject *kwds)
     }
     Py_DECREF(empty_tuple);
 
-    if (name) {
-        Py_INCREF(name);
-        Py_XSETREF(self->name, name);
-    }
-    if (path) {
-        Py_INCREF(path);
-        Py_XSETREF(self->path, path);
-    }
+    Py_XINCREF(name);
+    Py_XSETREF(self->name, name);
+
+    Py_XINCREF(path);
+    Py_XSETREF(self->path, path);
+
     if (PyTuple_GET_SIZE(args) == 1) {
         msg = PyTuple_GET_ITEM(args, 0);
         Py_INCREF(msg);
-        Py_XSETREF(self->msg, msg);
     }
+    Py_XSETREF(self->msg, msg);
 
     return 0;
 }