StructArray::try_new validation incorrectly returns an error when logical_nulls() returns Some() && null_count == 0 #7435
Description
Describe the bug
This logic in StructArray::try_new validates that if one of the child arrays in the StructArray has a null value that isn't properly masked by the parent, then it will be rejected with the error Found unmasked nulls for non-nullable StructArray field.
if !f.is_nullable() {
if let Some(a) = a.logical_nulls() {
!nulls.as_ref().map(|n| n.contains(&a)).unwrap_or_default() {
return Err(ArrowError::InvalidArgumentError(format!(
"Found unmasked nulls for non-nullable StructArray field {:?}",
f.name()
)));
}
}
}However, it is possible for a.logical_nulls() to return Some(_) and the NullBuffer itself to report that there aren't any nulls (null_count == 0), which leads StructArray::try_new to incorrectly report that it found unmasked nulls.
To Reproduce
#[test]
fn test_struct_array_logical_nulls() {
// Field is non-nullable
let field = Field::new("a", DataType::Int32, false);
let values = vec![1, 2, 3];
// Create a NullBuffer with all bits set to valid (true)
let nulls = NullBuffer::from(vec![true, true, true]);
let array = Int32Array::new(values.into(), Some(nulls));
let child = Arc::new(array) as ArrayRef;
assert!(child.logical_nulls().is_some());
assert_eq!(child.logical_nulls().unwrap().null_count(), 0);
let fields = Fields::from(vec![field]);
let arrays = vec![child];
let nulls = None;
drop(StructArray::try_new(fields, arrays, nulls).expect("should not error"));
}Expected behavior
The validation succeeds.
Additional context
I will raise a PR for this fix shortly.