fix: raise NotImplementedError instead of returning it (#2710)

Author: MarcoGorelli

narwhals/_arrow/utils.py

@@ -237,15 +237,11 @@ def extract_native(
     If one of the two sides has a `_broadcast` flag, then extract the scalar
     underneath it so that PyArrow can do its own broadcasting.
     """
-    from narwhals._arrow.dataframe import ArrowDataFrame
     from narwhals._arrow.series import ArrowSeries
 
     if rhs is None:  # pragma: no cover
         return lhs.native, lit(None, type=lhs._type)
 
-    if isinstance(rhs, ArrowDataFrame):
-        return NotImplemented
-
     if isinstance(rhs, ArrowSeries):
         if lhs._broadcast and not rhs._broadcast:
             return lhs.native[0], rhs.native

narwhals/_dask/utils.py

@@ -144,19 +144,19 @@ def narwhals_to_native_dtype(dtype: IntoDType, version: Version) -> Any:  # noqa
         return "timedelta64[ns]"
     if isinstance_or_issubclass(dtype, dtypes.List):  # pragma: no cover
         msg = "Converting to List dtype is not supported yet"
-        return NotImplementedError(msg)
+        raise NotImplementedError(msg)
     if isinstance_or_issubclass(dtype, dtypes.Struct):  # pragma: no cover
         msg = "Converting to Struct dtype is not supported yet"
-        return NotImplementedError(msg)
+        raise NotImplementedError(msg)
     if isinstance_or_issubclass(dtype, dtypes.Array):  # pragma: no cover
         msg = "Converting to Array dtype is not supported yet"
-        return NotImplementedError(msg)
+        raise NotImplementedError(msg)
     if isinstance_or_issubclass(dtype, dtypes.Time):  # pragma: no cover
         msg = "Converting to Time dtype is not supported yet"
-        return NotImplementedError(msg)
+        raise NotImplementedError(msg)
     if isinstance_or_issubclass(dtype, dtypes.Binary):  # pragma: no cover
         msg = "Converting to Binary dtype is not supported yet"
-        return NotImplementedError(msg)
+        raise NotImplementedError(msg)
 
     msg = f"Unknown dtype: {dtype}"  # pragma: no cover
     raise AssertionError(msg)

narwhals/_pandas_like/utils.py

@@ -93,14 +93,10 @@ def align_and_extract_native(
     If the comparison isn't supported, return `NotImplemented` so that the
     "right-hand-side" operation (e.g. `__radd__`) can be tried.
     """
-    from narwhals._pandas_like.dataframe import PandasLikeDataFrame
     from narwhals._pandas_like.series import PandasLikeSeries
 
     lhs_index = lhs.native.index
 
-    if isinstance(rhs, PandasLikeDataFrame):
-        return NotImplemented
-
     if lhs._broadcast and isinstance(rhs, PandasLikeSeries) and not rhs._broadcast:
         return lhs.native.iloc[0], rhs.native
 

narwhals/_utils.py

@@ -1770,7 +1770,8 @@ def __get__(
         # NOTE: Prefer not exposing the actual class we're defining in
         # `_implementation` may not be available everywhere
         who = getattr(instance, "_implementation", self._name_owner)
-        raise _not_implemented_error(self._name, who)
+        _raise_not_implemented_error(self._name, who)
+        return None  # pragma: no cover
 
     def __call__(self, *args: Any, **kwds: Any) -> Any:
         # NOTE: Purely to duck-type as assignable to **any** instance method
@@ -1793,13 +1794,13 @@ def deprecated(cls, message: LiteralString, /) -> Self:
         return deprecated(message)(obj)
 
 
-def _not_implemented_error(what: str, who: str, /) -> NotImplementedError:
+def _raise_not_implemented_error(what: str, who: str, /) -> NotImplementedError:
     msg = (
         f"{what!r} is not implemented for: {who!r}.\n\n"
         "If you would like to see this functionality in `narwhals`, "
         "please open an issue at: https://github.com/narwhals-dev/narwhals/issues"
     )
-    return NotImplementedError(msg)
+    raise NotImplementedError(msg)
 
 
 class requires:  # noqa: N801