nearestPointOnLine can return wrong endpoint when the target point is very far from the line

[mlc]

Given a LineString like this, with one endpoint in the North Atlantic ocean and one in the South Pacific:

{
  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "LineString",
    "coordinates": [
      [-96.80974, -58.32062],
      [-50.2464, 38.36643]
    ]
  }
}

and a target Point like this, in Europe,

{
  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "Point",
    "coordinates": [13.6023, 46.50646]
  }
}

the nearestPointOnLine function should return [-50.2464, 38.36643], the segment endpoint in the North Atlantic ocean, as it is much closer than the other endpoint (5173km vs 15348km), and no other point on the segment is closer.

However, instead, turf returns a point very close to (withing floating-point-precision error of) the South Pacific endpoint.

[smallsaucepan]

Thanks for picking this up @mlc. Yes, that's definitely not working in the case you've found. Before we press ahead with your PR would you mind if I do a little debugging of the current vector code? Would like to understand why that isn't working.

[mlc]

Thanks for having a look, @smallsaucepan! Obviously if you have a better solution than mine I am not offended if you take that instead!

[mlc]

For what it's worth, the only debugging hint I can offer is very small: the failing test case I provide fails even if you swap the order of the points on the input LineString, so it doesn't appear that the bug is e.g. preferring the first point to the second in certain circumstances.