fix: Implement to_arrow functionality properly for Arrays (#19077)

crates/polars-core/src/series/into.rs

@@ -85,6 +85,34 @@ impl Series {
                 );
                 Box::new(arr)
             },
+            #[cfg(feature = "dtype-array")]
+            DataType::Array(inner, width) => {
+                let ca = self.array().unwrap();
+                let arr = ca.chunks[chunk_idx].clone();
+                let arr = arr.as_any().downcast_ref::<FixedSizeListArray>().unwrap();
+
+                let new_values = if let DataType::Null = &**inner {
+                    arr.values().clone()
+                } else {
+                    let s = unsafe {
+                        Series::from_chunks_and_dtype_unchecked(
+                            PlSmallStr::EMPTY,
+                            vec![arr.values().clone()],
+                            &inner.to_physical(),
+                        )
+                        .cast_unchecked(inner)
+                        .unwrap()
+                    };
+
+                    s.to_arrow(0, compat_level)
+                };
+
+                let dtype =
+                    FixedSizeListArray::default_datatype(inner.to_arrow(compat_level), *width);
+                let arr =
+                    FixedSizeListArray::new(dtype, arr.len(), new_values, arr.validity().cloned());
+                Box::new(arr)
+            },
             #[cfg(feature = "dtype-categorical")]
             dt @ (DataType::Categorical(_, ordering) | DataType::Enum(_, ordering)) => {
                 let ca = self.categorical().unwrap();

py-polars/tests/unit/interop/test_interop.py

@@ -79,6 +79,32 @@ def test_arrow_list_chunked_array() -> None:
     assert s.dtype == pl.List
 
 
+# Test that polars convert Arrays of logical types correctly to arrow
+def test_arrow_array_logical() -> None:
+    # cast to large string and uint32 indices because polars converts to those
+    pa_data1 = (
+        pa.array(["a", "b", "c", "d"])
+        .dictionary_encode()
+        .cast(pa.dictionary(pa.uint32(), pa.large_string()))
+    )
+    pa_array_logical1 = pa.FixedSizeListArray.from_arrays(pa_data1, 2)
+
+    s1 = pl.Series(
+        values=[["a", "b"], ["c", "d"]],
+        dtype=pl.Array(pl.Enum(["a", "b", "c", "d"]), shape=2),
+    )
+    assert s1.to_arrow() == pa_array_logical1
+
+    pa_data2 = pa.array([date(2024, 1, 1), date(2024, 1, 2)])
+    pa_array_logical2 = pa.FixedSizeListArray.from_arrays(pa_data2, 1)
+
+    s2 = pl.Series(
+        values=[[date(2024, 1, 1)], [date(2024, 1, 2)]],
+        dtype=pl.Array(pl.Date, shape=1),
+    )
+    assert s2.to_arrow() == pa_array_logical2
+
+
 def test_from_dict() -> None:
     data = {"a": [1, 2], "b": [3, 4]}
     df = pl.from_dict(data)