fix: ast.NameConstant missing fields

[hunterhogan]

(.venv) C:\apps\astToolkit>py
Python 3.13.5 (tags/v3.13.5:6cb20a2, Jun 11 2025, 16:15:46) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import ast
>>> ast.Str._fields
<stdin>-1:1: DeprecationWarning: ast.Str is deprecated and will be removed in Python 3.14; use ast.Constant instead
('s',)
>>> ast.Bytes._fields
<stdin>-2:1: DeprecationWarning: ast.Bytes is deprecated and will be removed in Python 3.14; use ast.Constant instead
('s',)
>>> ast.Num._fields  
<stdin>-3:1: DeprecationWarning: ast.Num is deprecated and will be removed in Python 3.14; use ast.Constant instead
('n',)
>>> ast.NameConstant._fields
<stdin>-4:1: DeprecationWarning: ast.NameConstant is deprecated and will be removed in Python 3.14; use ast.Constant instead
('value', 'kind')

[brianschubert]

Hmm, I think these attributes are already inherited from Constant? Or am I missing something?

typeshed/stdlib/ast.pyi

Lines 1092 to 1096 in 3f727b0

	class Constant(expr):
	if sys.version_info >= (3, 10):
	__match_args__ = ("value", "kind")
	value: _ConstantValue
	kind: str | None

[hunterhogan]

Frankly, I don't know.

Elephant

By my count, there are five (deprecated) subclasses of ast.Constant. Of the five, only NameConstant has those two "attributes". (I'm intentionally avoiding _fields.)

(.venv) C:\apps\astToolFactory>py
Python 3.13.5 (tags/v3.13.5:6cb20a2, Jun 11 2025, 16:15:46) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import ast
>>> ast.Ellipsis._fields
<stdin>-1:1: DeprecationWarning: ast.Ellipsis is deprecated and will be removed in Python 3.14; use ast.Constant instead
()

The three in the first comment above have "attributes", and their attributes are defined in ast.pyi. Similarly, ast.Ellipsis does not seem to inherit anything from ast.Constant. Those things point towards a desire to add them to the stub.

Rhino

On the other hand, I don't know where ast.NameConstant is. I mean, it's not in Python.asdl, and I haven't searched super hard, but I don't know how any of the deprecated classes come to "exist". I just looked more closely at ast.py, and it seems to be flawed, also.

class Num(Constant, metaclass=_ABC):
    _fields = ('n',)
    __new__ = _new


class Str(Constant, metaclass=_ABC):
    _fields = ('s',)
    __new__ = _new


class Bytes(Constant, metaclass=_ABC):
    _fields = ('s',)
    __new__ = _new


class NameConstant(Constant, metaclass=_ABC):
    __new__ = _new


class Ellipsis(Constant, metaclass=_ABC):
    _fields = ()

https://github.com/python/cpython/blob/1e3466a1ae5bdcee42a3dfdbd8aaa17135a6ecc2/Lib/ast.py#L605-L622

It doesn't name the fields, but the interpreter knows the fields exist.

Elephino

So, I just now did _field_types on everything, and even ast.Ellipsis seems to have inherited from ast.Constant!

>>> ast.NameConstant._field_types
<stdin>-2:1: DeprecationWarning: ast.NameConstant is deprecated and will be removed in Python 3.14; use ast.Constant instead
{'value': <class 'object'>, 'kind': str | None}
>>> ast.Constant._field_types    
{'value': <class 'object'>, 'kind': str | None}
>>> ast.Num._field_types     
<stdin>-4:1: DeprecationWarning: ast.Num is deprecated and will be removed in Python 3.14; use ast.Constant instead
{'value': <class 'object'>, 'kind': str | None}
>>> ast.Str._field_types
<stdin>-5:1: DeprecationWarning: ast.Str is deprecated and will be removed in Python 3.14; use ast.Constant instead
{'value': <class 'object'>, 'kind': str | None}
>>> ast.Bytes._field_types
<stdin>-6:1: DeprecationWarning: ast.Bytes is deprecated and will be removed in Python 3.14; use ast.Constant instead
{'value': <class 'object'>, 'kind': str | None}
>>> ast.Ellipsis._field_types
{'value': <class 'object'>, 'kind': str | None}

I feel like the stub file helps to provide clarity and precision. If that is a goal, then I feel it suggests to add the "attributes" and their types.

On the other hand, I feel that the stub file should not be used to fix code that could be fixed directly.

I have a package, astToolfactory, that creates another package, astToolkit, mostly by using the ast module. I am also using the CPython asdl parser to parse "Python.asdl" and extract the match_args parameters for the classes. In astToolFactory, I was parsing "ast.pyi" with an ast.NodeVisitor I created through astToolkit, when I got an error because I expected to find type annotations for ast.NameConstant.value and ast.NameConstant.kind because for each of the ast.AST subclasses, I collected the "attribute" names from ast.class._fields. I think I am a character in "Being John Malkovich," written by Kurt Vonnegut, and adapted to cinema by Christopher Nolan. "Malkovich Malkovich ast Malkovich ast ast Malkovich Malkovich Malkovich."

[hunterhogan]

I just looked more closely at ast.py, and it seems to be flawed, also.

Or, it is not flawed because the intention was to let ast.NameConstant inherit from ast.Constant but to override the inheritance in the other four subclasses. But _field_types is still messed up for those four subclasses. Malkovich Malkovich Malkovich.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉