fix: nw.lit(date, dtype=nw.Date), loosen Dask minimum back to 2024.8 (#…

…1730)

narwhals/_dask/utils.py

@@ -136,6 +136,8 @@ def narwhals_to_native_dtype(dtype: DType | type[DType], version: Version) -> An
         return "category"
     if isinstance_or_issubclass(dtype, dtypes.Datetime):
         return "datetime64[us]"
+    if isinstance_or_issubclass(dtype, dtypes.Date):
+        return "date32[day][pyarrow]"
     if isinstance_or_issubclass(dtype, dtypes.Duration):
         return "timedelta64[ns]"
     if isinstance_or_issubclass(dtype, dtypes.List):  # pragma: no cover

narwhals/_pandas_like/utils.py

@@ -637,10 +637,11 @@ 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)
+        try:
+            import pyarrow as pa  # ignore-banned-import
+        except ModuleNotFoundError:  # pragma: no cover
+            msg = "PyArrow>=11.0.0 is required for `Date` dtype."
+        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:

narwhals/utils.py

@@ -293,7 +293,7 @@ def is_ibis(self) -> bool:
     Implementation.PYARROW: (11,),
     Implementation.PYSPARK: (3, 3),
     Implementation.POLARS: (0, 20, 3),
-    Implementation.DASK: (2024, 10),
+    Implementation.DASK: (2024, 8),
     Implementation.DUCKDB: (1,),
     Implementation.IBIS: (6,),
 }

pyproject.toml

@@ -33,7 +33,7 @@ cudf = ["cudf>=24.10.0"]
 pyarrow = ["pyarrow>=11.0.0"]
 pyspark = ["pyspark>=3.3.0"]
 polars = ["polars>=0.20.3"]
-dask = ["dask[dataframe]>=2024.10"]
+dask = ["dask[dataframe]>=2024.8"]
 duckdb = ["duckdb>=1.0"]
 ibis = ["ibis-framework>=6.0.0", "rich", "packaging", "pyarrow_hotfix"]
 dev = [

tests/expr_and_series/arithmetic_test.py

@@ -11,6 +11,7 @@
 from hypothesis import given
 
 import narwhals.stable.v1 as nw
+from tests.utils import DASK_VERSION
 from tests.utils import PANDAS_VERSION
 from tests.utils import Constructor
 from tests.utils import ConstructorEager
@@ -67,6 +68,8 @@ def test_right_arithmetic_expr(
     constructor: Constructor,
     request: pytest.FixtureRequest,
 ) -> None:
+    if "dask" in str(constructor) and DASK_VERSION < (2024, 10):
+        request.applymarker(pytest.mark.xfail)
     if attr == "__rmod__" and any(
         x in str(constructor) for x in ["pandas_pyarrow", "modin_pyarrow"]
     ):
@@ -241,6 +244,8 @@ def test_arithmetic_expr_left_literal(
     constructor: Constructor,
     request: pytest.FixtureRequest,
 ) -> None:
+    if "dask" in str(constructor) and DASK_VERSION < (2024, 10):
+        request.applymarker(pytest.mark.xfail)
     if attr == "__mod__" and any(
         x in str(constructor) for x in ["pandas_pyarrow", "modin_pyarrow"]
     ):

tests/expr_and_series/binary_test.py

@@ -1,11 +1,16 @@
 from __future__ import annotations
 
+import pytest
+
 import narwhals.stable.v1 as nw
+from tests.utils import DASK_VERSION
 from tests.utils import Constructor
 from tests.utils import assert_equal_data
 
 
-def test_expr_binary(constructor: Constructor) -> None:
+def test_expr_binary(constructor: Constructor, request: pytest.FixtureRequest) -> None:
+    if "dask" in str(constructor) and DASK_VERSION < (2024, 10):
+        request.applymarker(pytest.mark.xfail)
     data = {"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8, 9]}
     df_raw = constructor(data)
     result = nw.from_native(df_raw).with_columns(

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

@@ -1,12 +1,15 @@
 from __future__ import annotations
 
+from datetime import date
 from typing import TYPE_CHECKING
 from typing import Any
 
 import numpy as np
 import pytest
 
 import narwhals.stable.v1 as nw
+from tests.utils import DASK_VERSION
+from tests.utils import PANDAS_VERSION
 from tests.utils import Constructor
 from tests.utils import assert_equal_data
 
@@ -82,10 +85,27 @@ def test_lit_operation(
     col_name: str,
     expr: nw.Expr,
     expected_result: list[int],
+    request: pytest.FixtureRequest,
 ) -> None:
+    if (
+        "dask" in str(constructor)
+        and col_name in ("left_lit", "left_scalar")
+        and DASK_VERSION < (2024, 10)
+    ):
+        request.applymarker(pytest.mark.xfail)
     data = {"a": [1, 3, 2]}
     df_raw = constructor(data)
     df = nw.from_native(df_raw).lazy()
     result = df.select(expr.alias(col_name))
     expected = {col_name: expected_result}
     assert_equal_data(result, expected)
+
+
+@pytest.mark.skipif(PANDAS_VERSION < (1, 5), reason="too old for pyarrow")
+def test_date_lit(constructor: Constructor, request: pytest.FixtureRequest) -> None:
+    if "dask" in str(constructor):
+        # https://github.com/dask/dask/issues/11637
+        request.applymarker(pytest.mark.xfail)
+    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/expr_and_series/operators_test.py

@@ -3,6 +3,7 @@
 import pytest
 
 import narwhals.stable.v1 as nw
+from tests.utils import DASK_VERSION
 from tests.utils import Constructor
 from tests.utils import ConstructorEager
 from tests.utils import assert_equal_data
@@ -75,8 +76,17 @@ def test_logic_operators_expr(
     ],
 )
 def test_logic_operators_expr_scalar(
-    constructor: Constructor, operator: str, expected: list[bool]
+    constructor: Constructor,
+    operator: str,
+    expected: list[bool],
+    request: pytest.FixtureRequest,
 ) -> None:
+    if (
+        "dask" in str(constructor)
+        and DASK_VERSION < (2024, 10)
+        and operator in ("__rand__", "__ror__")
+    ):
+        request.applymarker(pytest.mark.xfail)
     data = {"a": [True, True, False, False]}
     df = nw.from_native(constructor(data))
 

tests/frame/select_test.py

@@ -118,7 +118,7 @@ def test_missing_columns(constructor: Constructor) -> None:
 def test_left_to_right_broadcasting(
     constructor: Constructor, request: pytest.FixtureRequest
 ) -> None:
-    if "dask" in str(constructor) and DASK_VERSION < (2024, 9):
+    if "dask" in str(constructor) and DASK_VERSION < (2024, 10):
         request.applymarker(pytest.mark.xfail)
     df = nw.from_native(constructor({"a": [1, 1, 2], "b": [4, 5, 6]}))
     result = df.select(nw.col("a") + nw.col("b").sum())

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")})

tests/tpch_q1_test.py

@@ -10,6 +10,7 @@
 import pytest
 
 import narwhals.stable.v1 as nw
+from tests.utils import DASK_VERSION
 from tests.utils import PANDAS_VERSION
 from tests.utils import assert_equal_data
 
@@ -20,6 +21,8 @@
 )
 @pytest.mark.filterwarnings("ignore:.*Passing a BlockManager.*:DeprecationWarning")
 def test_q1(library: str, request: pytest.FixtureRequest) -> None:
+    if library == "dask" and DASK_VERSION < (2024, 10):
+        request.applymarker(pytest.mark.xfail)
     if library == "pandas" and PANDAS_VERSION < (1, 5):
         request.applymarker(pytest.mark.xfail)
     elif library == "pandas":