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gh-144169: Fix three crashes in AST objects with non-str kwargs #144178

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gh-144169: Fix three crashes in AST objects with non-str kwargs #144178

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gh-144169: Fix three crashes in AST objects with non-str kwargs
JelleZijlstra Jan 23, 2026
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JelleZijlstra Jan 24, 2026
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28 changes: 28 additions & 0 deletions Lib/test/test_ast/test_ast.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1443,6 +1443,13 @@ def test_replace_reject_unknown_instance_fields(self):
self.assertIs(node.ctx, context)
self.assertRaises(AttributeError, getattr, node, 'unknown')

def test_replace_non_str_kwarg(self):
node = ast.Name(id="x")
errmsg = "got an unexpected keyword argument <object object"
with self.assertRaisesRegex(TypeError, errmsg):
node.__replace__(**{object(): "y"})


class ASTHelpers_Test(unittest.TestCase):
maxDiff = None

Expand Down Expand Up @@ -3304,6 +3311,27 @@ class _AllFieldTypes(ast.AST):
self.assertIs(obj.a, None)
self.assertEqual(obj.b, [])

def test_non_str_kwarg(self):
warn_msg = "got an unexpected keyword argument <object object"
with (
self.assertRaises(TypeError),
self.assertWarnsRegex(DeprecationWarning, warn_msg),
):
ast.Name(**{object(): 'y'})

class FakeStr:
def __init__(self, value):
self.value = value

def __hash__(self):
return hash(self.value)

def __eq__(self, other):
return isinstance(other, str) and self.value == other

with self.assertRaisesRegex(TypeError, "got multiple values for argument"):
ast.Name("x", **{FakeStr('id'): 'y'})


@support.cpython_only
class ModuleStateTests(unittest.TestCase):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-01-23-06-43-21.gh-issue-144169.LFy9yi.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix three crashes when non-string keyword arguments are supplied to objects
in the :mod:`ast` module.
6 changes: 3 additions & 3 deletions Parser/asdl_c.py
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Original file line number Diff line number Diff line change
Expand Up @@ -942,7 +942,7 @@ def visitModule(self, mod):
}
if (p == 0) {
PyErr_Format(PyExc_TypeError,
"%.400s got multiple values for argument '%U'",
"%.400s got multiple values for argument %R",
Py_TYPE(self)->tp_name, key);
Comment on lines +945 to 946
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@vstinner vstinner Jan 23, 2026

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Since we are modifying the error message, you must use the safer %T format:

Suggested change
"%.400s got multiple values for argument %R",
Py_TYPE(self)->tp_name, key);
"%T got multiple values for argument %R",
self, key);

Same remark for the two other changes below.

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@JelleZijlstra JelleZijlstra Jan 24, 2026

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It looks like this changes the error message to include the module name:

$ python3.14 -Wall -c 'import ast; ast.Name(idx=3)'
<string>:1: DeprecationWarning: Name.__init__ got an unexpected keyword argument 'idx'. Support for arbitrary keyword arguments is deprecated and will be removed in Python 3.15.
<string>:1: DeprecationWarning: Name.__init__ missing 1 required positional argument: 'id'. This will become an error in Python 3.15.
$ ./python.exe -Wall -c 'import ast; ast.Name(idx=3)'
<string>:1: DeprecationWarning: ast.Name.__init__ got an unexpected keyword argument 'idx'. Support for arbitrary keyword arguments is deprecated and will be removed in Python 3.15.
<string>:1: DeprecationWarning: ast.Name.__init__ missing 1 required positional argument: 'id'. This will become an error in Python 3.15.

I feel like that's a change we should only make in 3.15, not in the bugfix releases.

Why is %T safer?

res = -1;
goto cleanup;
Expand All @@ -965,7 +965,7 @@ def visitModule(self, mod):
else if (contains == 0) {
if (PyErr_WarnFormat(
PyExc_DeprecationWarning, 1,
"%.400s.__init__ got an unexpected keyword argument '%U'. "
"%.400s.__init__ got an unexpected keyword argument %R. "
"Support for arbitrary keyword arguments is deprecated "
"and will be removed in Python 3.15.",
Py_TYPE(self)->tp_name, key
Expand Down Expand Up @@ -1207,7 +1207,7 @@ def visitModule(self, mod):
if (rc == 0) {
PyErr_Format(PyExc_TypeError,
"%.400s.__replace__ got an unexpected keyword "
"argument '%U'.", Py_TYPE(self)->tp_name, key);
"argument %R.", Py_TYPE(self)->tp_name, key);
Py_DECREF(expecting);
return -1;
}
Expand Down
6 changes: 3 additions & 3 deletions Python/Python-ast.c
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