Bugs caused by similar or identical input geometries

[rf-]

I've been seeing some crashing bugs caused by specific inputs to union with version 0.8.0.

For example:

var coords1 = [
  [
    [
      [-118.49128246307373, 34.019483292435396],
      [-118.49096059799194, 34.019203176094535],
      [-118.49094450473785, 34.01912758898703],
      [-118.48823547363281, 34.016802140968366],
      [-118.487548828125, 34.017371278141994],
      [-118.487548828125, 34.01735794217727],
      [-118.48639011383057, 34.01833169712249],
      [-118.48449110984802, 34.019892349558305],
      [-118.487548828125, 34.022524496063156],
      [-118.487548828125, 34.02252330890177],
      [-118.48758637905121, 34.02255561892879],
      [-118.48968923091888, 34.02087941406322],
      [-118.490429520607, 34.020261388532035],
      [-118.49038660526276, 34.02022581858034],
      [-118.49128246307373, 34.019483292435396]
    ]
  ]
];

var coords2 = [
  [
    [-118.48639011383057, 34.01833169712249],
    [-118.48823547363281, 34.016802140968366],
    [-118.49094450473785, 34.01912758898703],
    [-118.49096059799194, 34.019203176094535],
    [-118.49128246307373, 34.019483292435396],
    [-118.49038660526276, 34.02022581858034],
    [-118.490429520607, 34.020261388532035],
    [-118.48968923091888, 34.02087941406322],
    [-118.48758637905121, 34.02255561892879],
    [-118.48449110984802, 34.019892349558305],
    [-118.48639011383057, 34.01833169712249]
  ]
];

var results = polygonClipping.union(coords1, coords2);

This seems to cause an infinite loop.

I thought the issue could be related to overly-precise coordinates, but I also see issues sometimes with rounded coordinates. For example, this input causes a SweepEvent comparison failed error:

var coords = [
  [
    [-118.46571, 34.025348],
    [-118.465871, 34.025308],
    [-118.465936, 34.025348],
    [-118.467899, 34.025348],
    [-118.468194, 34.025197],
    [-118.468983, 34.025174],
    [-118.469245, 34.025348],
    [-118.46571, 34.025348]
  ]
];

polygonClipping.union(
  JSON.parse(JSON.stringify(coords)),
  JSON.parse(JSON.stringify(coords))
); // or `polygonClipping.union(coords, coords)`

[rf-]

Here's another SweepEvent comparison failed case where the inputs are less similar, although one of them has a weird shape:

polygonClipping.union(
  [
    [
      [-118.46571, 34.025348],
      [-118.465871, 34.025308],
      [-118.465936, 34.025348],
      [-118.467899, 34.025348],
      [-118.468194, 34.025197],
      [-118.468983, 34.025174],
      [-118.469245, 34.025348],
      [-118.46571, 34.025348]
    ]
  ],
  [
    [
      [-118.464605, 34.02561],
      [-118.465871, 34.025308],
      [-118.466413, 34.02565],
      [-118.467722, 34.025468],
      [-118.468194, 34.025197],
      [-118.468983, 34.025174],
      [-118.469433, 34.025494],
      [-118.470297, 34.025512],
      [-118.472282, 34.027219],
      [-118.464605, 34.02561]
    ]
  ]
);

[mfogel]

Thanks for the bug(s) @rf-

[mfogel]

The two sets of coordinates above for which polygon-clipping is throwing a SweepEvent comparison failed error I think are a subcase of #48 (which I just opened). I'll move those coordinates over to that issue and follow up with them there.

The first set of coordinates above (the one that results in the infinite loop) I think is a different error, this issue will track the problem with that first set of coordinates.

[rowanwins]

Both the bugs above are resolved by this commit

[mfogel]

Verified all these coordinates now work. Fix will be included in next release to NPM.