fix(typing): Narrow TypeVar used in Series

narwhals/functions.py

@@ -61,6 +61,7 @@
     from narwhals.typing import IntoSeriesT
     from narwhals.typing import NativeFrame
     from narwhals.typing import NativeLazyFrame
+    from narwhals.typing import NativeSeries
     from narwhals.typing import _2DArray
 
     _IntoSchema: TypeAlias = "Mapping[str, DType] | Schema | Sequence[str] | None"
@@ -240,7 +241,7 @@ def _new_series_impl(
     else:  # pragma: no cover
         native_namespace = implementation.to_native_namespace()
         try:
-            native_series = native_namespace.new_series(name, values, dtype)
+            native_series: NativeSeries = native_namespace.new_series(name, values, dtype)
             return from_native(native_series, series_only=True).alias(name)
         except AttributeError as e:
             msg = "Unknown namespace is expected to implement `new_series` constructor."
@@ -325,7 +326,7 @@ def _from_dict_impl(
         try:
             # implementation is UNKNOWN, Narwhals extension using this feature should
             # implement `from_dict` function in the top-level namespace.
-            native_frame = native_namespace.from_dict(data, schema=schema)
+            native_frame: NativeFrame = native_namespace.from_dict(data, schema=schema)
         except AttributeError as e:
             msg = "Unknown namespace is expected to implement `from_dict` function."
             raise AttributeError(msg) from e
@@ -441,7 +442,7 @@ def _from_numpy_impl(
         try:
             # implementation is UNKNOWN, Narwhals extension using this feature should
             # implement `from_numpy` function in the top-level namespace.
-            native_frame = native_namespace.from_numpy(data, schema=schema)
+            native_frame: NativeFrame = native_namespace.from_numpy(data, schema=schema)
         except AttributeError as e:
             msg = "Unknown namespace is expected to implement `from_numpy` function."
             raise AttributeError(msg) from e
@@ -529,7 +530,7 @@ def _from_arrow_impl(
         try:
             # implementation is UNKNOWN, Narwhals extension using this feature should
             # implement PyCapsule support
-            native_frame = native_namespace.DataFrame(data)
+            native_frame: NativeFrame = native_namespace.DataFrame(data)
         except AttributeError as e:
             msg = "Unknown namespace is expected to implement `DataFrame` class which accepts object which supports PyCapsule Interface."
             raise AttributeError(msg) from e

narwhals/stable/v1/__init__.py

@@ -100,6 +100,7 @@
     from narwhals.typing import _2DArray
 
     FrameT = TypeVar("FrameT", "DataFrame[Any]", "LazyFrame[Any]")
+    SeriesT = TypeVar("SeriesT", bound="Series[Any]")
     IntoSeriesT = TypeVar("IntoSeriesT", bound="IntoSeries", default=Any)
     T = TypeVar("T", default=Any)
 else:
@@ -1154,6 +1155,10 @@ def _stableify(
     return obj
 
 
+@overload
+def from_native(native_object: SeriesT, **kwds: Any) -> SeriesT: ...
+
+
 @overload
 def from_native(
     native_object: IntoDataFrameT | IntoSeriesT,
@@ -1540,7 +1545,7 @@ def from_native(
 ) -> Any: ...
 
 
-def from_native(
+def from_native(  # noqa: D417
     native_object: IntoFrameT | IntoFrame | IntoSeriesT | IntoSeries | T,
     *,
     strict: bool | None = None,
@@ -1549,6 +1554,7 @@ def from_native(
     eager_or_interchange_only: bool = False,
     series_only: bool = False,
     allow_series: bool | None = None,
+    **kwds: Any,
 ) -> LazyFrame[IntoFrameT] | DataFrame[IntoFrameT] | Series[IntoSeriesT] | T:
     """Convert `native_object` to Narwhals Dataframe, Lazyframe, or Series.
 
@@ -1608,6 +1614,9 @@ def from_native(
     pass_through = validate_strict_and_pass_though(
         strict, pass_through, pass_through_default=False, emit_deprecation_warning=False
     )
+    if kwds:
+        msg = f"from_native() got an unexpected keyword argument {next(iter(kwds))!r}"
+        raise TypeError(msg)
 
     result = _from_native_impl(
         native_object,

narwhals/translate.py

@@ -50,6 +50,7 @@
     from narwhals.typing import IntoLazyFrameT
     from narwhals.typing import IntoSeries
     from narwhals.typing import IntoSeriesT
+    from narwhals.typing import SeriesT
 
 T = TypeVar("T")
 
@@ -128,6 +129,10 @@ def to_native(
     return narwhals_object
 
 
+@overload
+def from_native(native_object: SeriesT, **kwds: Any) -> SeriesT: ...
+
+
 @overload
 def from_native(
     native_object: IntoDataFrameT | IntoSeries,
@@ -298,14 +303,15 @@ def from_native(
 ) -> Any: ...
 
 
-def from_native(
+def from_native(  # noqa: D417
     native_object: IntoLazyFrameT | IntoFrameT | IntoSeriesT | IntoFrame | IntoSeries | T,
     *,
     strict: bool | None = None,
     pass_through: bool | None = None,
     eager_only: bool = False,
     series_only: bool = False,
     allow_series: bool | None = None,
+    **kwds: Any,
 ) -> LazyFrame[IntoLazyFrameT] | DataFrame[IntoFrameT] | Series[IntoSeriesT] | T:
     """Convert `native_object` to Narwhals Dataframe, Lazyframe, or Series.
 
@@ -351,6 +357,9 @@ def from_native(
     pass_through = validate_strict_and_pass_though(
         strict, pass_through, pass_through_default=False, emit_deprecation_warning=True
     )
+    if kwds:
+        msg = f"from_native() got an unexpected keyword argument {next(iter(kwds))!r}"
+        raise TypeError(msg)
 
     return _from_native_impl(  # type: ignore[no-any-return]
         native_object,

narwhals/typing.py

@@ -102,7 +102,7 @@ def __native_namespace__(self) -> ModuleType: ...
     ...     return df.columns
 """
 
-IntoSeries: TypeAlias = Union["Series[Any]", "NativeSeries"]
+IntoSeries: TypeAlias = "NativeSeries"
 """Anything which can be converted to a Narwhals Series.
 
 Use this if your function can accept an object which can be converted to `nw.Series`
@@ -176,6 +176,7 @@ def __native_namespace__(self) -> ModuleType: ...
 """
 
 LazyFrameT = TypeVar("LazyFrameT", bound="LazyFrame[Any]")
+SeriesT = TypeVar("SeriesT", bound="Series[Any]")
 
 IntoSeriesT = TypeVar("IntoSeriesT", bound="IntoSeries")
 """TypeVar bound to object convertible to Narwhals Series.

tests/translate/from_native_test.py

@@ -5,6 +5,7 @@
 from importlib.util import find_spec
 from typing import TYPE_CHECKING
 from typing import Any
+from typing import Callable
 from typing import Iterable
 from typing import Literal
 from typing import cast
@@ -18,6 +19,7 @@
 
 if TYPE_CHECKING:
     from typing_extensions import Self
+    from typing_extensions import assert_type
 
     from narwhals.utils import Version
 
@@ -360,10 +362,63 @@ def test_from_native_lazyframe() -> None:
     stable_lazy = nw.from_native(lf_pl)
     unstable_lazy = unstable_nw.from_native(lf_pl)
     if TYPE_CHECKING:
-        from typing_extensions import assert_type
-
         assert_type(stable_lazy, nw.LazyFrame[pl.LazyFrame])
         assert_type(unstable_lazy, unstable_nw.LazyFrame[pl.LazyFrame])
 
     assert isinstance(stable_lazy, nw.LazyFrame)
     assert isinstance(unstable_lazy, unstable_nw.LazyFrame)
+
+
+def test_series_recursive() -> None:
+    """https://github.com/narwhals-dev/narwhals/issues/2239."""
+    pytest.importorskip("polars")
+    import polars as pl
+
+    pl_series = pl.Series(name="test", values=[1, 2, 3])
+    nw_series = unstable_nw.from_native(pl_series, series_only=True)
+    with pytest.raises(AssertionError):
+        unstable_nw.Series(nw_series, level="full")
+
+    nw_series_early_return = unstable_nw.from_native(nw_series, series_only=True)
+
+    if TYPE_CHECKING:
+        assert_type(pl_series, pl.Series)
+        assert_type(nw_series, unstable_nw.Series[pl.Series])
+
+        nw_series_depth_2 = unstable_nw.Series(nw_series, level="full")  # type: ignore[var-annotated]
+        # NOTE: Checking that the type is `Series[Unknown]`
+        assert_type(nw_series_depth_2, unstable_nw.Series)  # type: ignore[type-arg]
+        assert_type(nw_series_early_return, unstable_nw.Series[pl.Series])
+
+
+def test_series_recursive_v1() -> None:
+    """https://github.com/narwhals-dev/narwhals/issues/2239."""
+    pytest.importorskip("polars")
+    import polars as pl
+
+    pl_series = pl.Series(name="test", values=[1, 2, 3])
+    nw_series = nw.from_native(pl_series, series_only=True)
+    with pytest.raises(AssertionError):
+        nw.Series(nw_series, level="full")
+
+    nw_series_early_return = nw.from_native(nw_series, series_only=True)
+
+    if TYPE_CHECKING:
+        assert_type(pl_series, pl.Series)
+        assert_type(nw_series, nw.Series[pl.Series])
+
+        nw_series_depth_2 = nw.Series(nw_series, level="full")
+        # NOTE: `Unknown` isn't possible for `v1`, as it has a `TypeVar` default
+        assert_type(nw_series_depth_2, nw.Series[Any])
+        assert_type(nw_series_early_return, nw.Series[pl.Series])
+
+
+@pytest.mark.parametrize("from_native", [unstable_nw.from_native, nw.from_native])
+def test_from_native_invalid_keywords(from_native: Callable[..., Any]) -> None:
+    pattern = r"from_native.+unexpected.+keyword.+bad_1"
+
+    with pytest.raises(TypeError, match=pattern):
+        from_native(data, bad_1="invalid")
+
+    with pytest.raises(TypeError, match=pattern):
+        from_native(data, bad_1="invalid", bad_2="also invalid")