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gh-133783: Fix __replace__ on AST nodes for optional attributes (#133797)

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Jelle Zijlstra 2025-05-10 09:17:38 -07:00 • committed by GitHub
parent 47f1722d80
commit 7dddb4e667
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9
Lib/test/test_ast/test_ast.py
View file

@ -1315,6 +1315,15 @@ class CopyTests(unittest.TestCase):
self.assertIs(repl.id, 'y')
self.assertIs(repl.ctx, context)
def test_replace_accept_missing_field_with_default(self):
node = ast.FunctionDef(name="foo", args=ast.arguments())
self.assertIs(node.returns, None)
self.assertEqual(node.decorator_list, [])
node2 = copy.replace(node, name="bar")
self.assertEqual(node2.name, "bar")
self.assertIs(node2.returns, None)
self.assertEqual(node2.decorator_list, [])
def test_replace_reject_known_custom_instance_fields_commits(self):
node = ast.parse('x').body[0].value
node.extra = extra = object() # add instance 'extra' field

3
Misc/NEWS.d/next/Library/2025-05-09-19-05-24.gh-issue-133783.1voCnR.rst Normal file
View file

@ -0,0 +1,3 @@
Fix bug with applying :func:`copy.replace` to :mod:`ast` objects. Attributes
that default to ``None`` were incorrectly treated as required for manually
created AST nodes.

26
Parser/asdl_c.py
View file

@ -1244,6 +1244,32 @@ ast_type_replace_check(PyObject *self,
Py_DECREF(unused);
}
}
// Discard fields from 'expecting' that default to None
PyObject *field_types = NULL;
if (PyObject_GetOptionalAttr((PyObject*)Py_TYPE(self),
&_Py_ID(_field_types),
&field_types) < 0)
{
Py_DECREF(expecting);
return -1;
}
if (field_types != NULL) {
Py_ssize_t pos = 0;
PyObject *field_name, *field_type;
while (PyDict_Next(field_types, &pos, &field_name, &field_type)) {
if (_PyUnion_Check(field_type)) {
// optional field
if (PySet_Discard(expecting, field_name) < 0) {
Py_DECREF(expecting);
Py_DECREF(field_types);
return -1;
}
}
}
Py_DECREF(field_types);
}
// Now 'expecting' contains the fields or attributes
// that would not be filled inside ast_type_replace().
Py_ssize_t m = PySet_GET_SIZE(expecting);

26
Python/Python-ast.c generated
View file

@ -5528,6 +5528,32 @@ ast_type_replace_check(PyObject *self,
Py_DECREF(unused);
}
}
// Discard fields from 'expecting' that default to None
PyObject *field_types = NULL;
if (PyObject_GetOptionalAttr((PyObject*)Py_TYPE(self),
&_Py_ID(_field_types),
&field_types) < 0)
{
Py_DECREF(expecting);
return -1;
}
if (field_types != NULL) {
Py_ssize_t pos = 0;
PyObject *field_name, *field_type;
while (PyDict_Next(field_types, &pos, &field_name, &field_type)) {
if (_PyUnion_Check(field_type)) {
// optional field
if (PySet_Discard(expecting, field_name) < 0) {
Py_DECREF(expecting);
Py_DECREF(field_types);
return -1;
}
}
}
Py_DECREF(field_types);
}
// Now 'expecting' contains the fields or attributes
// that would not be filled inside ast_type_replace().
Py_ssize_t m = PySet_GET_SIZE(expecting);