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stubtest: basic support for unpack kwargs #21024

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19 changes: 18 additions & 1 deletion mypy/stubtest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -941,7 +941,24 @@ def from_funcitem(stub: nodes.FuncItem) -> Signature[nodes.Argument]:
elif stub_arg.kind == nodes.ARG_STAR:
stub_sig.varpos = stub_arg
elif stub_arg.kind == nodes.ARG_STAR2:
stub_sig.varkw = stub_arg
if stub_arg.variable.type is not None and isinstance(
(typed_dict_arg := mypy.types.get_proper_type(stub_arg.variable.type)),
mypy.types.TypedDictType,
):
for key_name, key_type in typed_dict_arg.items.items():
stub_sig.kwonly[key_name] = nodes.Argument(
nodes.Var(key_name, key_type),
type_annotation=key_type,
initializer=(
nodes.EllipsisExpr()
if key_name not in typed_dict_arg.required_keys
else None
),
kind=nodes.ARG_NAMED,
pos_only=False,
Comment on lines +949 to +958
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@brianschubert brianschubert Mar 15, 2026

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Testing this locally, I think you need to set kind to ARG_NAMED_OPT too for optional parameters to be handled correctly.

Suggested change
stub_sig.kwonly[key_name] = nodes.Argument(
nodes.Var(key_name, key_type),
type_annotation=key_type,
initializer=(
nodes.EllipsisExpr()
if key_name not in typed_dict_arg.required_keys
else None
),
kind=nodes.ARG_NAMED,
pos_only=False,
optional = key_name not in typed_dict_arg.required_keys
stub_sig.kwonly[key_name] = nodes.Argument(
nodes.Var(key_name, key_type),
type_annotation=key_type,
initializer=nodes.EllipsisExpr() if optional else None,
kind=nodes.ARG_NAMED_OPT if optional else nodes.ARG_NAMED,
pos_only=False,

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@brianschubert brianschubert Mar 15, 2026

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(I'm also not sure if setting initializer=nodes.EllipsisExpr() is necessary. I wasn't able to find a difference between using EllipsisExpr vs always using None)

)
else:
stub_sig.varkw = stub_arg
else:
raise AssertionError
return stub_sig
Expand Down
22 changes: 22 additions & 0 deletions mypy/test/teststubtest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,7 @@ def __getitem__(self, typeargs: Any) -> object: ...
Final = 0
Literal = 0
TypedDict = 0
Unpack = 0

class TypeVar:
def __init__(self, name, covariant: bool = ..., contravariant: bool = ...) -> None: ...
Expand Down Expand Up @@ -765,6 +766,27 @@ def test_varargs_varkwargs(self) -> Iterator[Case]:
error="k6",
)

@collect_cases
def test_kwargs_unpack_typeddict(self) -> Iterator[Case]:
yield Case(
stub="""
from typing import TypedDict, Unpack

class _Args(TypedDict):
Comment on lines +773 to +775
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@brianschubert brianschubert Mar 15, 2026

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So that I won't have to update #19574 again :-)

Suggested change
from typing import TypedDict, Unpack
class _Args(TypedDict):
from typing import TypedDict, Unpack, type_check_only
@type_check_only
class _Args(TypedDict):

a: int
b: int

def f1(**kwargs: Unpack[_Args]) -> None: ...
""",
runtime="def f1(*, a, b): pass",
error=None,
)
yield Case(
stub="def f2(**kwargs: Unpack[_Args]) -> None: ...",
runtime="def f2(*, a, c): pass",
error="f2",
)
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@brianschubert brianschubert Mar 15, 2026

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I'd suggest adding some cases for mismatched optional parameters (e.g. optional in the TypedDict but required at runtime, and vice versa)


@collect_cases
def test_overload(self) -> Iterator[Case]:
yield Case(
Expand Down
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