fix: propagate validity when cast primitive to list (#11846)

crates/polars-arrow/src/compute/cast/mod.rs

@@ -520,7 +520,12 @@ pub fn cast(
             // Safety: offsets _are_ monotonically increasing
             let offsets = unsafe { Offsets::new_unchecked(offsets) };
 
-            let list_array = ListArray::<i64>::new(to_type.clone(), offsets.into(), values, None);
+            let list_array = ListArray::<i64>::new(
+                to_type.clone(),
+                offsets.into(),
+                values,
+                array.validity().cloned(),
+            );
 
             Ok(Box::new(list_array))
         },

py-polars/tests/unit/datatypes/test_list.py

@@ -468,10 +468,10 @@ def test_list_recursive_categorical_cast() -> None:
 @pytest.mark.parametrize(
     ("data", "expected_data", "dtype"),
     [
-        ([1, 2], [[1], [2]], pl.Int64),
-        ([1.0, 2.0], [[1.0], [2.0]], pl.Float64),
-        (["x", "y"], [["x"], ["y"]], pl.Utf8),
-        ([True, False], [[True], [False]], pl.Boolean),
+        ([None, 1, 2], [None, [1], [2]], pl.Int64),
+        ([None, 1.0, 2.0], [None, [1.0], [2.0]], pl.Float64),
+        ([None, "x", "y"], [None, ["x"], ["y"]], pl.Utf8),
+        ([None, True, False], [None, [True], [False]], pl.Boolean),
     ],
 )
 def test_non_nested_cast_to_list(

py-polars/tests/unit/series/test_series.py

@@ -243,6 +243,18 @@ def test_equal() -> None:
     assert s3.dt.convert_time_zone("Asia/Tokyo").series_equal(s4) is True
 
 
+@pytest.mark.parametrize(
+    "dtype",
+    [pl.Int64, pl.Float64, pl.Utf8, pl.Boolean],
+)
+def test_eq_missing_list_and_primitive(dtype: PolarsDataType) -> None:
+    s1 = pl.Series([None, None], dtype=dtype)
+    s2 = pl.Series([None, None], dtype=pl.List(dtype))
+
+    expected = pl.Series([True, True])
+    assert_series_equal(s1.eq_missing(s2), expected)
+
+
 def test_to_frame() -> None:
     s1 = pl.Series([1, 2])
     s2 = pl.Series("s", [1, 2])