feat: Add DataFrame.clone for pyarrow (#2288)

Author: dangotbanned

narwhals/_arrow/dataframe.py

@@ -666,7 +666,8 @@ def collect(
         msg = f"Unsupported `backend` value: {backend}"  # pragma: no cover
         raise AssertionError(msg)  # pragma: no cover
 
-    clone = not_implemented()
+    def clone(self) -> Self:
+        return self._from_native_frame(self.native, validate_column_names=False)
 
     def item(self: Self, row: int | None, column: int | str | None) -> Any:
         from narwhals._arrow.series import maybe_extract_py_scalar

tests/frame/clone_test.py

@@ -1,21 +1,19 @@
 from __future__ import annotations
 
-import pytest
-
 import narwhals.stable.v1 as nw
 from tests.utils import ConstructorEager
 from tests.utils import assert_equal_data
 
 
-def test_clone(
-    request: pytest.FixtureRequest, constructor_eager: ConstructorEager
-) -> None:
-    if "pyarrow_table" in str(constructor_eager):
-        request.applymarker(pytest.mark.xfail)
-
+def test_clone(constructor_eager: ConstructorEager) -> None:
     expected = {"a": [1, 2], "b": [3, 4]}
+    expected_mod = {"a": [1, 2], "b": [3, 4], "c": [4, 6]}
     df = nw.from_native(constructor_eager(expected), eager_only=True)
     df_clone = df.clone()
     assert df is not df_clone
     assert df._compliant_frame is not df_clone._compliant_frame
     assert_equal_data(df_clone, expected)
+    df_clone_mod = df_clone.with_columns((nw.col("a") + nw.col("b")).alias("c"))
+    assert_equal_data(df, expected)
+    assert_equal_data(df_clone, expected)
+    assert_equal_data(df_clone_mod, expected_mod)