if dtype=None, use library default

Author: MarcoGorelli

narwhals/_arrow/namespace.py

@@ -181,9 +181,6 @@ def _lit_arrow_series(_: ArrowDataFrame) -> ArrowSeries:
             )
             if dtype:
                 return arrow_series.cast(dtype)
-            elif isinstance(value, str) and dtype is None:
-                # Cast to nw.String() to ensure we default to large-string.
-                return arrow_series.cast(import_dtypes_module(self._version).String())
             return arrow_series
 
         return ArrowExpr(

tests/expr_and_series/lit_test.py

@@ -135,6 +135,6 @@ def test_date_lit(constructor: Constructor, request: pytest.FixtureRequest) -> N
 def test_pyarrow_lit_string() -> None:
     df = nw.from_native(pa.table({"a": [1, 2, 3]}))
     result = df.select(nw.lit("foo")).to_native().schema.field("literal")
-    assert pa.types.is_large_string(result.type)
+    assert pa.types.is_string(result.type)
     result = df.select(nw.lit("foo", dtype=nw.String)).to_native().schema.field("literal")
     assert pa.types.is_large_string(result.type)