ci: bump mypy to 2.1.0, pyrefly to 1.0

pyproject.toml

@@ -77,8 +77,8 @@ typing = [  # keep some of these pinned and bump periodically so there's fewer s
   "pytest",
   "pandas-stubs==2.3.0.250703",
   "typing_extensions",
-  "mypy~=1.15.0",
-  "pyrefly==0.64.0",
+  "mypy==2.1.0",
+  "pyrefly==1.0.0",
   "pyright",
   "pyarrow-stubs==19.2",
   "narwhals[dask]",
@@ -322,6 +322,7 @@ exclude_also = [
   'if "(cudf|modin|pyspark|ibis)" in',
   "if not .*.is_pandas",
   "if is_ibis_table",
+  "if MYPY",
   "except ModuleNotFoundError",
   'request.applymarker\(pytest.mark.xfail',
   'backend_version <',
@@ -386,6 +387,7 @@ ignore = [
   "../../../**/Lib",      # stdlib
   "../../../**/typeshed*" # typeshed-fallback
 ]
+defineConstant = { "MYPY" = false }
 
 [tool.pyrefly]
 search-path = ["src", "."]

src/narwhals/_arrow/dataframe.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Collection, Iterator, Mapping, Sequence
-from typing import TYPE_CHECKING, Any, Literal, cast, overload
+from typing import TYPE_CHECKING, Any, Final, Literal, cast, overload
 
 import pyarrow as pa
 import pyarrow.compute as pc
@@ -77,6 +77,8 @@
         "full outer",
     ]
 
+MYPY: Final = False
+
 
 class ArrowDataFrame(
     EagerDataFrame["ArrowSeries", "ArrowExpr", "pa.Table", "ChunkedArrayAny"]
@@ -320,6 +322,8 @@ def _select_multi_index(
         # **Doesn't accept `ndarray`**
         elif is_numpy_array_1d(columns):
             selector = columns.tolist()
+        elif MYPY:
+            selector = columns  # type: ignore[assignment]
         else:
             selector = columns
         return self._with_native(self.native.select(selector))

src/narwhals/_compliant/dataframe.py

@@ -2,7 +2,7 @@
 
 from collections.abc import Iterator, Mapping, Sequence, Sized
 from itertools import chain
-from typing import TYPE_CHECKING, Any, Literal, Protocol, TypeVar, overload
+from typing import TYPE_CHECKING, Any, Final, Literal, Protocol, TypeVar, overload
 
 from narwhals._compliant.typing import (
     CompliantDataFrameAny,
@@ -80,6 +80,8 @@
 
     Incomplete: TypeAlias = Any
 
+MYPY: Final = False
+
 __all__ = ["CompliantDataFrame", "CompliantFrame", "CompliantLazyFrame", "EagerDataFrame"]
 
 T = TypeVar("T")
@@ -434,11 +436,18 @@ def __getitem__(  # noqa: C901, PLR0912
                 else:
                     compliant = compliant._select_multi_index(columns)
             elif isinstance(columns, slice):
-                compliant = compliant._select_slice_name(columns)
+                if MYPY:
+                    # https://github.com/python/mypy/issues/21508
+                    compliant = compliant._select_slice_name(columns)  # type: ignore[arg-type]
+                else:
+                    compliant = compliant._select_slice_name(columns)
             elif is_compliant_series(columns):
                 compliant = self._select_multi_name(columns.native)
             elif is_sequence_like(columns):
                 compliant = self._select_multi_name(columns)
+            elif MYPY:
+                # https://github.com/python/mypy/issues/21508
+                pass
             else:
                 assert_never(columns)
 
@@ -450,7 +459,11 @@ def __getitem__(  # noqa: C901, PLR0912
             elif is_compliant_series(rows):
                 compliant = compliant._gather(rows.native)
             elif is_sized_multi_index_selector(rows):
-                compliant = compliant._gather(rows)
+                if MYPY:  # noqa: SIM108
+                    # https://github.com/python/mypy/issues/21508
+                    compliant = compliant._gather(rows)  # type: ignore[arg-type]
+                else:
+                    compliant = compliant._gather(rows)
             else:
                 assert_never(rows)
 

src/narwhals/_compliant/group_by.py

@@ -161,7 +161,8 @@ def _remap_expr_name(
         Arguments:
             name: Name of a `nw.Expr` aggregation method.
         """
-        return cls._REMAP_AGGS.get(name, name)
+        result: NativeAggregationT_co = cls._REMAP_AGGS.get(name, name)
+        return result
 
     @classmethod
     def _leaf_name(cls, expr: DepthTrackingExprAny, /) -> NarwhalsAggregation | Any:

src/narwhals/_compliant/series.py

@@ -347,7 +347,8 @@ class EagerSeriesStructNamespace(  # type: ignore[misc]
 ): ...
 
 
-class EagerSeriesHist(Protocol[NativeSeriesT, _CountsT_co]):
+# mypy says: `Covariant type variable "_CountsT_co" used in protocol where invariant one is expected`
+class EagerSeriesHist(Protocol[NativeSeriesT, _CountsT_co]):  # type: ignore[misc]
     _series: EagerSeries[NativeSeriesT]
     _breakpoint: bool
     _data: HistData[NativeSeriesT, _CountsT_co]

src/narwhals/_dask/expr.py

@@ -715,5 +715,5 @@ def dt(self) -> DaskExprDateTimeNamespace:
     last = not_implemented()
 
     # namespaces
-    list: not_implemented = not_implemented()  # type: ignore[assignment]
-    struct: not_implemented = not_implemented()  # type: ignore[assignment]
+    list: Any = not_implemented()
+    struct: Any = not_implemented()

src/narwhals/_duration.py

@@ -57,8 +57,7 @@ def to_timedelta(
             msg = f"Creating timedelta with {self.unit} unit is not supported."
             raise NotImplementedError(msg)
         kwd = UNIT_TO_TIMEDELTA[self.unit]
-        # error: Keywords must be strings (bad mypy)
-        return dt.timedelta(**{kwd: self.multiple})  # type: ignore[misc]
+        return dt.timedelta(**{kwd: self.multiple})
 
     @classmethod
     def parse(cls, every: str) -> Interval:

src/narwhals/_pandas_like/dataframe.py

@@ -1180,7 +1180,7 @@ def pivot(
         remapped = self._pivot_remap_column_names(
             columns, n_on=len(on), n_values=len(values), separator=separator
         )
-        result.columns = remapped  # type: ignore[assignment]
+        result.columns = remapped
         result.columns.names = [""]
         return self._with_native(result.reset_index())
 

src/narwhals/_polars/dataframe.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Iterator, Mapping, Sequence, Sized
-from typing import TYPE_CHECKING, Any, Generic, Literal, TypeVar, cast, overload
+from typing import TYPE_CHECKING, Any, Final, Generic, Literal, TypeVar, cast, overload
 
 import polars as pl
 
@@ -64,6 +64,8 @@
     T = TypeVar("T")
     R = TypeVar("R")
 
+MYPY: Final = False
+
 Method: TypeAlias = "Callable[..., R]"
 """Generic alias representing all methods implemented via `__getattr__`.
 
@@ -222,7 +224,7 @@ def join(
         return self._with_native(
             self.native.join(
                 other=other.native,
-                how=how_native,  # type: ignore[arg-type]
+                how=how_native,
                 left_on=left_on,
                 right_on=right_on,
                 suffix=suffix,
@@ -495,11 +497,11 @@ def __getitem__(  # noqa: C901, PLR0912
                     else:
                         native = native[:, columns]
                 elif isinstance(columns, slice):
-                    native = native.select(
-                        self.columns[
-                            slice(*convert_str_slice_to_int_slice(columns, self.columns))
-                        ]
-                    )
+                    if MYPY:
+                        int_slice = convert_str_slice_to_int_slice(columns, self.columns)  # type: ignore[arg-type]
+                    else:
+                        int_slice = convert_str_slice_to_int_slice(columns, self.columns)
+                    native = native.select(self.columns[slice(*int_slice)])
                 elif is_compliant_series(columns):
                     native = native.select(columns.native.to_list())
                 elif is_sequence_like(columns):

src/narwhals/_polars/namespace.py

@@ -237,7 +237,7 @@ class PolarsSelectorNamespace:
     def __init__(self, context: _LimitedContext, /) -> None:
         self._version = context._version
 
-    def by_dtype(self, dtypes: Iterable[DType]) -> PolarsExpr:
+    def by_dtype(self, dtypes: Iterable[IntoDType]) -> PolarsExpr:
         native_dtypes = [
             narwhals_to_native_dtype(dtype, self._version).__class__
             if isinstance(dtype, type) and issubclass(dtype, DType)

src/narwhals/_polars/utils.py

@@ -2,7 +2,7 @@
 
 import abc
 from functools import lru_cache
-from typing import TYPE_CHECKING, Any, ClassVar, Final, Protocol, TypeVar, overload
+from typing import TYPE_CHECKING, Any, ClassVar, Final, Protocol, TypeVar, cast, overload
 
 import polars as pl
 
@@ -73,7 +73,7 @@ def extract_native(obj: _StoresNative[NativeT]) -> NativeT: ...
 @overload
 def extract_native(obj: T) -> T: ...
 def extract_native(obj: _StoresNative[NativeT] | T) -> NativeT | T:
-    return obj.native if _is_compliant_polars(obj) else obj
+    return obj.native if _is_compliant_polars(obj) else cast("T", obj)
 
 
 def _is_compliant_polars(

test-plugin/test_plugin/dataframe.py

@@ -47,10 +47,10 @@ def _with_version(self, version: Version) -> Self:
     __native_namespace__ = not_implemented()
 
     # Properties
-    schema = not_implemented()  # type: ignore[assignment]
+    schema: Any = not_implemented()
 
     # Static
-    _is_native = not_implemented()  # type: ignore[assignment]
+    _is_native = not_implemented()
 
     # Helpers
     _iter_columns = not_implemented()

tests/expr_and_series/over_test.py

@@ -245,7 +245,7 @@ def test_over_anonymous_cumulative(
     context = (
         pytest.raises(NotImplementedError)
         if df.implementation.is_pyarrow()
-        else pytest.raises(KeyError)  # type: ignore[arg-type]
+        else pytest.raises(KeyError)
         if df.implementation.is_modin()
         or (df.implementation.is_pandas() and PANDAS_VERSION < (1, 3))
         # TODO(unassigned): bug in old pandas + modin.

tests/v1_test.py

@@ -591,7 +591,8 @@ def __dataframe__(self) -> None:  # pragma: no cover
 
     mockdf = MockDf()
     result = nw_v1.from_native(mockdf, eager_only=True, strict=False)
-    assert result is mockdf
+    # mypy issue?
+    assert result is mockdf  # type: ignore[comparison-overlap]
 
 
 def test_from_native_lazyframe() -> None: