Unexpected arguments type error

[eupraxis1981]

Below code provides example:

MergeStrategy = NamedTuple(
typename="MergeStrategy",
fields=[("left", str), ("right", str), ("how", str), ("on", List[str])],
)
Generates error
{
"resource": <>,
"owner": "python",
"code": "error",
"severity": 8,
"message": "Unexpected arguments to namedtuple()",
"source": "mypy",
"startLineNumber": 53,
"startColumn": 18,
"endLineNumber": 53,
"endColumn": 18
}

whereas this does not:
MergeStrategy = NamedTuple(
"MergeStrategy", [("left", str), ("right", str), ("how", str), ("on", List[str])],
)

Same thing for regular namedtuple.

get same error with this:
MergeStrategy = namedtuple(typename="MergeStrategy", field_names=["left", "right", "how", "on"])

but this is fine:
MergeStrategy = namedtuple("MergeStrategy", ["left", "right", "how", "on"])

[hauntsaninja]

Shouldn't be too hard to fix, look at parse_namedtuple_args in semanal_namedtuple.py. Not sure if mypy's AST has the equivalent of inspect.Signature.bind, but that would make it really easy.

[momohatt]

I was investigating this issue and noticed that the keyword arguments typename and fields are deprecated for typing.NamedTuple (python/cpython#16222)

It seems that these keyword arguments are still allowed for the regular namedtuple, though.

[gvanrossum]

More than deprecated -- typing.NamedTuple now markes these as positional args only. But collections.namedtuple is unchanged. Not sure if there's anything actionable left here?

[momohatt]

Yes, I'm not sure if mypy should support these keyword arguments for collections.namedtuple when typing.NamedTuple doesn't accept it...
Still, it might be a good idea to elaborate the error message like: error: mypy does not support keyword arguments 'typename' and 'field_names' for namedtuple()