test: cover CUDA e2e null-mask export

Make the cuDF e2e fixture export a nullable primitive column and validate that the host Arrow round-trip preserves its nulls.

Keep the other fixture columns non-nullable so this test stays focused on the null-mask path that CI exercises through cuDF.

Signed-off-by: Alexander Droste <alexander.droste@protonmail.com>

Author: 0ax1

vortex-test/e2e-cuda/src/lib.rs

@@ -68,7 +68,7 @@ pub unsafe extern "C" fn export_array(
 ) -> i32 {
     let mut ctx = CudaSession::create_execution_ctx(&SESSION).unwrap();
 
-    let primitive = PrimitiveArray::from_iter(0u32..5);
+    let primitive = PrimitiveArray::from_option_iter([Some(0u32), None, Some(2), Some(3), None]);
     let decimal = DecimalArray::from_iter(0i128..5, DecimalDType::new(38, 2));
     let strings = VarBinViewArray::from_iter_str([
         "one",
@@ -124,7 +124,7 @@ pub unsafe extern "C" fn validate_array(
     let array = make_array(array_data);
     let struct_array = array.as_struct();
 
-    let primitive = UInt32Array::from_iter(0..5);
+    let primitive = UInt32Array::from_iter([Some(0), None, Some(2), Some(3), None]);
     let decimal = Decimal128Array::from_iter_values(0..5)
         .with_precision_and_scale(38, 2)
         .expect("with_precision_and_scale");
@@ -138,7 +138,7 @@ pub unsafe extern "C" fn validate_array(
     let date = Date32Array::from(vec![100i32, 200, 300, 400, 500]);
 
     let expected_fields = Fields::from_iter([
-        Field::new("prims", primitive.data_type().clone(), false),
+        Field::new("prims", primitive.data_type().clone(), true),
         Field::new("decimals", decimal.data_type().clone(), false),
         Field::new("strings", string.data_type().clone(), false),
         Field::new("dates", date.data_type().clone(), false),