Voronoi diagram contains collection with a LineString

[martinfleis]

I've found a pathological case where the result of voronoi polygons contains LineStrings. See the example below, using shapely built against GEOS 3.12.1.

import shapely

points_input = shapely.MultiPoint(
    (
        (-819831.1, -1007946.473), 
        (-819831.1, -1007945.994),
        (-819829.184, -1007947.9099999999),
        (-819829.663, -1007947.9099999999),
    )
)
voronoi = shapely.voronoi_polygons(
    points_input
)
shapely.get_parts(voronoi)

array([<POLYGON ((-819827.268 -1007944.078, -819827.268 -1007949.826, -819829.424 -...>,
       <POLYGON ((-819833.016 -1007944.078, -819827.268 -1007944.078, -819829.424 -...>,
       <POLYGON ((-819833.016 -1007949.826, -819833.016 -1007946.234, -819829.424 -...>,
       <GEOMETRYCOLLECTION (POLYGON ((-819833.016 -1007949.826, -819829.424 -100794...>],
      dtype=object)

The last collection contains a Polygon and a tiny LineString, but the presence of the LineString causes failure when using coverage union later.

The issue is most likely caused by the floating point in those y coords and setting the precision grid resolves it (edit: it does in this case but not in others I've found). But I don't think that the algorithm should result in a LineString in any situation.