fix(geojson): ignore zero area geometries

geojson/RegionCoverer.ts

@@ -4,6 +4,7 @@ import { CellUnion } from '../s2/CellUnion'
 import { fromGeoJSON } from './geometry'
 import { Polyline } from '../s2/Polyline'
 import { Polygon } from '../s2/Polygon'
+import { Rect } from '../s2/Rect'
 import type { Region } from '../s2/Region'
 import type { RegionCovererOptions as S2RegionCovererOptions } from '../s2/RegionCoverer'
 import { RegionCoverer as S2RegionCoverer } from '../s2/RegionCoverer'
@@ -81,8 +82,14 @@ export class RegionCoverer {
 
     let union = new CellUnion()
     shapes.forEach((shape: Region) => {
+      const area = RegionCoverer.area(shape)
+      const isPolygon = shape instanceof Polygon
+
+      // discard zero-area polygons
+      if (isPolygon && area <= 0) return
+
       // optionally elect to use a fast covering method for small areas
-      const fast = union.length >= this.memberCoverer.maxCells && RegionCoverer.area(shape) < this.smallAreaEpsilon
+      const fast = union.length >= this.memberCoverer.maxCells && area < this.smallAreaEpsilon
       const cov = fast ? this.memberCoverer.fastCovering(shape) : this.memberCoverer.covering(shape)
 
       // discard errorneous members which cover the entire planet
@@ -104,16 +111,21 @@ export class RegionCoverer {
     const shape = fromGeoJSON(geometry)
     if (Array.isArray(shape)) return this.mutliMemberCovering(shape as Region[])
 
+    // discard zero-area polygons
+    if (shape instanceof Polygon && RegionCoverer.area(shape) <= 0) return new CellUnion()
+
     // discard errorneous shapes which cover the entire planet
     const cov = this.coverer.covering(shape)
     if (!RegionCoverer.validCovering(shape, cov)) return new CellUnion()
+
     return cov
   }
 
   /** Computes the area of a shape */
   private static area(shape: Region): number {
     if (shape instanceof Polygon) return shape.area()
     if (shape instanceof Polyline) shape.capBound().area()
+    if (shape instanceof Rect) shape.capBound().area()
     return 0
   }
 

geojson/RegionCoverer_test.ts

@@ -1,6 +1,6 @@
 import type * as geojson from 'geojson'
 import { test, describe } from 'node:test'
-import { deepEqual } from 'node:assert/strict'
+import { ok, deepEqual } from 'node:assert/strict'
 import { RegionCoverer } from './RegionCoverer'
 import * as cellid from '../s2/cellid'
 
@@ -147,6 +147,120 @@ describe('RegionCoverer', () => {
     deepEqual([...union.map(cellid.toToken)], [])
   })
 
+  test('multipolygon - second ring is invalid & should be ignored', (t) => {
+    const mpolygon: geojson.MultiPolygon = {
+      type: 'MultiPolygon',
+      coordinates: [
+        [
+          [
+            [-82.463379, 28.07198],
+            [-82.468872, 28.07198],
+            [-82.468872, 28.07198],
+            [-82.474369, 28.07198],
+            [-82.473222, 28.070161],
+            [-82.469386, 28.057119],
+            [-82.470504, 28.055128],
+            [-82.474365, 28.054253],
+            [-82.475276, 28.054321],
+            [-82.479858, 28.052591],
+            [-82.481073, 28.052591],
+            [-82.485352, 28.047743],
+            [-82.485352, 28.047743],
+            [-82.485352, 28.047743],
+            [-82.489631, 28.042894],
+            [-82.490355, 28.042894],
+            [-82.493591, 28.044561],
+            [-82.497859, 28.043243],
+            [-82.502753, 28.037698],
+            [-82.507658, 28.035846],
+            [-82.508323, 28.0346],
+            [-82.508892, 28.032724],
+            [-82.509084, 28.030773],
+            [-82.508892, 28.028823],
+            [-82.508323, 28.026947],
+            [-82.507399, 28.025218],
+            [-82.506156, 28.023702],
+            [-82.50464, 28.022459],
+            [-82.502911, 28.021535],
+            [-82.501035, 28.020966],
+            [-82.499084, 28.020773],
+            [-82.497134, 28.020966],
+            [-82.495258, 28.021535],
+            [-82.493529, 28.022459],
+            [-82.492013, 28.023702],
+            [-82.49077, 28.025218],
+            [-82.490395, 28.025919],
+            [-82.490377, 28.025914],
+            [-82.490049, 28.025814],
+            [-82.488098, 28.025622],
+            [-82.486147, 28.025814],
+            [-82.484271, 28.026383],
+            [-82.482542, 28.027307],
+            [-82.481027, 28.028551],
+            [-82.479858, 28.029975],
+            [-82.47869, 28.028551],
+            [-82.478443, 28.028349],
+            [-82.468266, 28.028349],
+            [-82.466125, 28.033198],
+            [-82.466125, 28.034935],
+            [-82.463379, 28.038046],
+            [-82.463379, 28.038046],
+            [-82.463379, 28.041511],
+            [-82.463379, 28.042895],
+            [-82.463379, 28.047047],
+            [-82.463225, 28.047569],
+            [-82.460632, 28.046981],
+            [-82.454902, 28.04828],
+            [-82.45407, 28.050167],
+            [-82.455139, 28.052591],
+            [-82.455139, 28.057438],
+            [-82.45565, 28.058595],
+            [-82.46045, 28.061315],
+            [-82.45935, 28.070039],
+            [-82.458494, 28.07198],
+            [-82.463379, 28.07198],
+            [-82.463379, 28.07198]
+          ]
+        ],
+        [
+          [
+            [-82.505951, 28.075921],
+            [-82.507902, 28.075729],
+            [-82.509778, 28.07516],
+            [-82.511507, 28.074236],
+            [-82.513022, 28.072993],
+            [-82.514266, 28.071477],
+            [-82.51519, 28.069748],
+            [-82.515759, 28.067872],
+            [-82.515951, 28.065921],
+            [-82.515759, 28.063971],
+            [-82.51519, 28.062095],
+            [-82.514644, 28.061074],
+            [-82.513285, 28.061074],
+            [-82.506411, 28.062632],
+            [-82.505495, 28.062286],
+            [-82.501831, 28.060902],
+            [-82.499539, 28.060036],
+            [-82.496338, 28.061591],
+            [-82.495524, 28.062513],
+            [-82.4957, 28.06471],
+            [-82.495524, 28.066905],
+            [-82.503457, 28.075897],
+            [-82.504578, 28.075786],
+            [-82.505951, 28.075921]
+          ]
+        ]
+      ]
+    }
+    const cov = new RegionCoverer({ maxLevel: 15 })
+    const union = cov.covering(mpolygon)
+    ok(!union.includes(1152921505680588800n), 'contains null island cellid') // null island
+    deepEqual(
+      [...union.map(cellid.toToken)],
+      ['88c2c08b4', '88c2c08d', '88c2c093', '88c2c095', '88c2c0c1', '88c2c0c3', '88c2c0ec', '88c2c0f4']
+    )
+  })
+
   test('linestring - should generate covering', (t) => {
     const linestring: geojson.LineString = {
       type: 'LineString',