fix: nw.lit(date, dtype=nw.Date)

narwhals/_pandas_like/utils.py

@@ -637,10 +637,7 @@ def narwhals_to_native_dtype(  # noqa: PLR0915
             else f"timedelta64[{du_time_unit}]"
         )
     if isinstance_or_issubclass(dtype, dtypes.Date):
-        if dtype_backend == "pyarrow-nullable":
-            return "date32[pyarrow]"
-        msg = "Date dtype only supported for pyarrow-backed data types in pandas"
-        raise NotImplementedError(msg)
+        return "date32[pyarrow]"
     if isinstance_or_issubclass(dtype, dtypes.Enum):
         msg = "Converting to Enum is not (yet) supported"
         raise NotImplementedError(msg)

narwhals/expr.py

@@ -7023,7 +7023,7 @@ def all_horizontal(*exprs: IntoExpr | Iterable[IntoExpr]) -> Expr:
     )
 
 
-def lit(value: Any, dtype: DType | None = None) -> Expr:
+def lit(value: Any, dtype: DType | type[DType] | None = None) -> Expr:
     """Return an expression representing a literal value.
 
     Arguments:

narwhals/stable/v1/__init__.py

@@ -2542,7 +2542,7 @@ def len() -> Expr:
     return _stableify(nw.len())
 
 
-def lit(value: Any, dtype: DType | None = None) -> Expr:
+def lit(value: Any, dtype: DType | type[DType] | None = None) -> Expr:
     """Return an expression representing a literal value.
 
     Arguments:

tests/frame/lit_test.py → tests/expr_and_series/lit_test.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from datetime import date
 from typing import TYPE_CHECKING
 from typing import Any
 
@@ -89,3 +90,9 @@ def test_lit_operation(
     result = df.select(expr.alias(col_name))
     expected = {col_name: expected_result}
     assert_equal_data(result, expected)
+
+
+def test_date_lit(constructor: Constructor) -> None:
+    df = nw.from_native(constructor({"a": [1]}))
+    result = df.with_columns(nw.lit(date(2020, 1, 1), dtype=nw.Date)).collect_schema()
+    assert result == {"a": nw.Int64, "literal": nw.Date}

tests/series_only/cast_test.py

@@ -98,18 +98,6 @@ def test_cast_date_datetime_pandas() -> None:
     assert df.schema == {"a": nw.Date}
 
 
-@pytest.mark.skipif(
-    PANDAS_VERSION < (2, 0, 0),
-    reason="pyarrow dtype not available",
-)
-def test_cast_date_datetime_invalid() -> None:
-    # pandas: pyarrow datetime to date
-    dfpd = pd.DataFrame({"a": [datetime(2020, 1, 1), datetime(2020, 1, 2)]})
-    df = nw.from_native(dfpd)
-    with pytest.raises(NotImplementedError, match="pyarrow"):
-        df.select(nw.col("a").cast(nw.Date))
-
-
 @pytest.mark.filterwarnings("ignore: casting period")
 def test_unknown_to_int() -> None:
     df = pd.DataFrame({"a": pd.period_range("2000", periods=3, freq="min")})