Thanks for the detailed writeup @senritsu

Haven't heavily tested yet, however we ran into this issue in our codebase and swapping for simplify-geojson seems to work.

https://github.com/maxogden/simplify-geojson

Is this still an issue with v6.2.0? If so I can try to come up with a reproducible case to help.

Thanks for the tip @mbullington - I believe it's still an issue. Would be interestenig to run a benchmark against simplify-geojson and the current turf (which is a wrapper around simplify.js)

Got this issue today, the problem is still here.

From my point of view simplify-geojson (https://github.com/maxogden/simplify-geojson) is just very tiny wrapper around simplify-geometry (https://github.com/seabre/simplify-geometry) and does not really provide any usefull code. simplify-geometry is an alternative to simplify-js.

So if turfjs wants to switch I would switch directly to simplify-geometry (simplify-geojson does not provide anything).

But the real question is what the code should produce when non-valid linear ring is returned from simplify-js/simplify-geometry and from my point of view it would be much better just to return an invalid polygon, let the user of the library handle it.

I was able to also reproduce this using the following geometry:

{
  type: 'Feature',
  properties: {},
  geometry: { type: 'Polygon', coordinates: [
  [
    [ 4.0881641, 6.8121605 ],
    [ 4.0881639, 6.8121607 ],
    [ 4.0881638, 6.8121608 ],
    [ 4.0881641, 6.8121605 ]
  ]
] }
}

I was able to reproduce this issue using the following code

const turf = require("@turf/turf");
const simplifyOptions = { tolerance: 0.00001, highQuality: true };
turf.simplify(
  {
    type: "Feature",
    properties: { },
    geometry: {
      type: "MultiPolygon",
      coordinates: [
        [
            [
                [-10.06762725, -17.428977611],
                [-10.067626613, -17.428977323],
                [-10.067625943, -17.428976957],
                [-10.06762725, -17.428977611]
              ]
            ],
            [
              [
                [-10.067625943, -17.428976957],
                [-10.067599027, -17.428963499],
                [-10.067625941, -17.428976956],
                [-10.067625943, -17.428976957]
              ]
        ],
      ],
    },
  },
  simplifyOptions
);

Any updates?

same for me, unfortunately! Maybe MultiPolygons are the issue? At least for me it loops on a MultiPolygon too .
update: nope, sometimes it works with MultiPolygons, so it must be something else

@rowanwins could you take a look?

Suspect this might be related to issues in cleanCoords. Just waiting for a couple of other PRs to merge first.