turf intersect: Each LinearRing of a Polygon must have 4 or more Positions

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• GeoJSON data as a gist file or geojson.io (filename extension must be .geojson).
• Snippet of source code or for complex examples use jsfiddle.

Hello,

I have an error with turf/intersect. Is that something I am doing wrong or a bug?

Thank you

const intersect = require("@turf/intersect").default;

const geoJson1 = {
  type: "Feature",
  properties: {
    code: "65242"
  },
  geometry: {
    type: "Polygon",
    coordinates: [
      [
        [0.141179, 43.36818], [0.148728, 43.367642], [0.153978, 43.367941], [0.15406, 43.368879], [0.163409, 43.371427], [0.162531, 43.370615], [0.165807, 43.367931], [0.166334, 43.362561], [0.168195, 43.361501], [0.168578, 43.357791], [0.170263, 43.356262], [0.173148, 43.3492], [0.165161, 43.34775], [0.157626, 43.342611], [0.152694, 43.342085], [0.149333, 43.342992], [0.145901, 43.341962], [0.140744, 43.342316], [0.140504, 43.344645], [0.134485, 43.344652], [0.13974, 43.358065], [0.142917, 43.357494], [0.14257, 43.359911], [0.140389, 43.363775], [0.141179, 43.36818]
      ]
    ]
  }
};

const geoJson2 = {
  type: "Feature",
  properties: {},
  geometry: {
    type: "MultiPolygon",
    coordinates: [
      [
        [
          [-0.003511817426206, 43.4699897941247], [-0.003510675548367, 43.379992017286], [0.086492457141402, 43.3799922060496], [0.086492395200926, 43.2899938575523], [0.266499564242721, 43.2899958347523], [0.266498422976084, 43.3799936438263], [0.176495463022904, 43.3799924051132], [0.176494466412028, 43.4699904648683], [-0.003511817426206, 43.4699897941247]
        ],
        [
          [0.221496676867966, 43.3259988784034], [0.221497305021322, 43.3439979092252], [0.248497229697336, 43.3439977847358], [0.248498037469127, 43.3259979174387], [0.221496676867966, 43.3259988784034]
        ],
        [
          [0.149494714775711, 43.3169980868321], [0.149495737551508, 43.3259972246487], [0.140494074719633, 43.3259972052475], [0.140494667441234, 43.3439967446387], [0.131494370741759, 43.3439970882588], [0.131493979866131, 43.3529964603265], [0.122493641497581, 43.3529971097641], [0.122494266127063, 43.370996144705], [0.158495319359878, 43.3709970371161], [0.158494333168507, 43.3619965574681], [0.194496359336044, 43.361996882516], [0.194496951739768, 43.3169982443264], [0.149494714775711, 43.3169980868321]
        ]
      ]
    ]
  }
};

intersect(geoJson1, geoJson2);

Throws an error:

Error: Each LinearRing of a Polygon must have 4 or more Positions.
    at Object.polygon (/test-turf/node_modules/@turf/helpers/index.js:213:19)
    at intersect (/test-turf/node_modules/@turf/intersect/index.js:62:34)
    at intersect (/test-turf/node_modules/@turf/intersect/index.js:74:35)
    at intersect (/test-turf/node_modules/@turf/intersect/index.js:102:16)
    at Object.<anonymous> (/test-turf/index.js:88:1)
    at Module._compile (internal/modules/cjs/loader.js:734:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:745:10)
    at Module.load (internal/modules/cjs/loader.js:626:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:566:12)
    at Function.Module._load (internal/modules/cjs/loader.js:558:3)

[frastlin]

The error that is thrown when you don’t have any internal rings is “Each LinearRing of a Polygon must have 4 or more Positions”. There should be another check to throw an error if there are no rings that says something like: “Each polygon must have at least one internal ring of 4 or more positions.”

[stebogit]

@frastlin a full validation of GeoJSON object is expected to be done by the user before using any Turf modules. The @turf/boolean-valid module (which might not be perfect) was added to do that.

In other words, Turf modules generally expect valid inputs. Checking if the Polygon’s coordinates array contains an array of (valid) LinearRings or (valid) coordinates is not trivial, so it is best keeping that outside the scope of the intersect module, in this case.