Union can't join touching polygons on anti-meridian

[zdila]

Turf 7.1.0

Union can't join touching polygons on anti-meridian unless coordinates are adjusted by 360.

// CORRECT - produces {"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":[[[-183,67.35710304434852],[-180,64.8381209933682],[-173,67.35710304434852],[-180,69.40628708036891],[-183,67.35710304434852]]]}}

union(featureCollection([polygon([
    [
      [-180, 64.8381209933682],
      [-185, 67.35710304434852],
      [-180, 69.40628708036891],
      [-180, 64.8381209933682],
    ],
  ]), polygon([
    [
      [-180, 64.8381209933682],
      [-173, 67.35710304434852],
      [-180, 69.40628708036891],
      [-180, 64.8381209933682],
    ]
  ])]));

// INCORRECT - produces {"type":"Feature","properties":{},"geometry":{"type":"MultiPolygon","coordinates":[[[[-180,64.8381209933682],[-173,67.35710304434852],[-180,69.40628708036891],[-180,64.8381209933682]]],[[[173,67.35710304434852],[180,64.8381209933682],[180,69.40628708036891],[173,67.35710304434852]]]]}}

union(featureCollection([polygon([
    [
      [180, 64.8381209933682],
      [175, 67.35710304434852],
      [180, 69.40628708036891],
      [180, 64.8381209933682]
    ]
  ]), polygon([
    [
      [-180, 64.8381209933682],
      [-173, 67.35710304434852],
      [-180, 69.40628708036891],
      [-180, 64.8381209933682],
    ]
  ])]));

[smallsaucepan]

Thanks for raising this @zdila. I think Turf is doing the right thing by not generating a single polygon that spans the antemeridian. Looking at the Antimeridian Cutting section of the Geojson spec returning a multipolygon is the best for compatibility.

I know that doesn't make much sense given your use case though, so happy to hear if you have a different perspective or suggested behaviour.