Function union_soup_with 

pub fn union_soup_with(
    rings: &[Ring],
    tolerance: Tolerance,
    options: OverlayOptions,
) -> Result<ReportedUnion, OverlayError>

union_soup with explicit options; the default options make it union_soup exactly.

With OverlayOptions::dropping_degenerate_rings a ring that is too short, has a repeated vertex, or has zero area under the exact ZeroArea rule is left out and reported in ReportedUnion::dropped, as overlay_with does (#256): operand OverlayOperand::Subject, polygon the ring’s index, role RingRole::Outer. Every other fault is refused as by union_soup.