fix(great-circle): fix antimeridian splitting by upgrading arc to v1.0.0

packages/turf-great-circle/README.md

@@ -17,8 +17,7 @@ then a `LineString` will be returned with duplicate coordinates the length of th
 
     *   `options.properties` **[Object][4]** line feature properties (optional, default `{}`)
     *   `options.npoints` **[number][5]** number of points (optional, default `100`)
-    *   `options.offset` **[number][5]** offset controls the likelyhood that lines will
-        be split which cross the dateline. The higher the number the more likely. (optional, default `10`)
+    *   `options.offset` **[number][5]?** NOTE: deprecated: Antimeridian splitting is now automatic and this option has no effect
 
 ### Examples
 

packages/turf-great-circle/index.ts

@@ -22,8 +22,7 @@ import { GreatCircle } from "arc";
  * @param {Object} [options={}] Optional parameters
  * @param {Object} [options.properties={}] line feature properties
  * @param {number} [options.npoints=100] number of points
- * @param {number} [options.offset=10] offset controls the likelyhood that lines will
- * be split which cross the dateline. The higher the number the more likely.
+ * @param {number} [options.offset] NOTE: deprecated: Antimeridian splitting is now automatic and this option has no effect
  * @returns {Feature<LineString | MultiLineString>} great circle line feature
  * @example
  * var start = turf.point([-122, 48]);
@@ -45,7 +44,7 @@ function greatCircle(
 ): Feature<LineString | MultiLineString> {
   // Optional parameters
   if (typeof options !== "object") throw new Error("options is invalid");
-  const { properties = {}, npoints = 100, offset = 10 } = options;
+  const { properties = {}, npoints = 100 } = options;
 
   const startCoord = getCoord(start);
   const endCoord = getCoord(end);
@@ -61,7 +60,7 @@ function greatCircle(
     properties || {}
   );
 
-  const line = generator.Arc(npoints, { offset: offset });
+  const line = generator.Arc(npoints);
 
   return line.json() as Feature<
     LineString | MultiLineString,

packages/turf-great-circle/package.json

@@ -73,7 +73,7 @@
     "@turf/helpers": "workspace:*",
     "@turf/invariant": "workspace:*",
     "@types/geojson": "catalog:",
-    "arc": "^0.2.0",
+    "arc": "^1.0.0",
     "tslib": "catalog:"
   }
 }

packages/turf-great-circle/test.ts

@@ -7,6 +7,7 @@ import { writeJsonFileSync } from "write-json-file";
 import type {
   FeatureCollection,
   LineString,
+  MultiLineString,
   Feature,
   Geometry,
   Point,
@@ -40,6 +41,12 @@ function getStartEndPoints(fixture: (typeof fixtures)[0]) {
   return { start, end };
 }
 
+function getFixture(name: string) {
+  const fixture = fixtures.find((f) => f.name === name);
+  if (!fixture) throw new Error(`fixture not found: ${name}`);
+  return fixture;
+}
+
 test("turf-great-circle", (t) => {
   fixtures.forEach((fixture) => {
     const name = fixture.name;
@@ -77,7 +84,7 @@ test("turf-great-circle with same input and output", (t) => {
 });
 
 test("turf-great-circle accepts Feature<Point> inputs", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
+  const { start, end } = getStartEndPoints(getFixture("basic"));
   t.doesNotThrow(
     () => greatCircle(start, end),
     "accepts Feature<Point> inputs"
@@ -86,7 +93,7 @@ test("turf-great-circle accepts Feature<Point> inputs", (t) => {
 });
 
 test("turf-great-circle accepts Point geometry inputs", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
+  const { start, end } = getStartEndPoints(getFixture("basic"));
   t.doesNotThrow(
     () => greatCircle(start.geometry, end.geometry),
     "accepts Point geometry inputs"
@@ -95,7 +102,7 @@ test("turf-great-circle accepts Point geometry inputs", (t) => {
 });
 
 test("turf-great-circle accepts Position inputs", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
+  const { start, end } = getStartEndPoints(getFixture("basic"));
   t.doesNotThrow(
     () => greatCircle(start.geometry.coordinates, end.geometry.coordinates),
     "accepts Position inputs"
@@ -104,7 +111,7 @@ test("turf-great-circle accepts Position inputs", (t) => {
 });
 
 test("turf-great-circle applies custom properties", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
+  const { start, end } = getStartEndPoints(getFixture("basic"));
   const withProperties = greatCircle(start, end, {
     properties: { name: "Test Route" },
   });
@@ -117,7 +124,7 @@ test("turf-great-circle applies custom properties", (t) => {
 });
 
 test("turf-great-circle respects npoints option", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
+  const { start, end } = getStartEndPoints(getFixture("basic"));
   const withCustomPoints = greatCircle(start, end, { npoints: 5 });
   t.equal(
     (withCustomPoints.geometry as LineString).coordinates.length,
@@ -127,13 +134,12 @@ test("turf-great-circle respects npoints option", (t) => {
   t.end();
 });
 
-test("turf-great-circle respects offset and npoints options", (t) => {
-  const { start, end } = getStartEndPoints(fixtures[0]);
-  const withOffset = greatCircle(start, end, { offset: 100, npoints: 10 });
-  t.equal(
-    (withOffset.geometry as LineString).coordinates.length,
-    10,
-    "respects offset and npoints options"
+test("turf-great-circle offset option is accepted but has no effect", (t) => {
+  const { start, end } = getStartEndPoints(getFixture("basic"));
+  // NOTE: offset is deprecated and a no-op since arc@1.0.0; antimeridian splitting is automatic with a MultiLineString result when needed. This test ensures that the option is accepted without throwing, but does not verify any behavior since it has no effect.
+  t.doesNotThrow(
+    () => greatCircle(start, end, { offset: 100, npoints: 10 }),
+    "accepts offset option without throwing"
   );
   t.end();
 });
@@ -150,3 +156,41 @@ test("turf-great-circle with antipodal start and end", (t) => {
 
   t.end();
 });
+
+// Antimeridian crossing fixtures. Each route crosses the international dateline and must produce a MultiLineString with segments that close and open exactly at ±180°.
+[
+  "antimeridian-tokyo-lax",
+  "antimeridian-auckland-lax",
+  "antimeridian-shanghai-sfo",
+].forEach((fixtureName) => {
+  test(`turf-great-circle antimeridian split: ${fixtureName}`, (t) => {
+    const { start, end } = getStartEndPoints(getFixture(fixtureName));
+    // NOTE: npoints=10 reproduces the original bug https://github.com/Turfjs/turf/issues/3030 (also confirmed by @jgravois)
+    const result = greatCircle(start, end, { npoints: 10 });
+    const geom = result.geometry as MultiLineString;
+
+    t.equal(
+      geom.type,
+      "MultiLineString",
+      "produces MultiLineString across antimeridian"
+    );
+
+    const lastOfFirst = geom.coordinates[0].at(-1)!;
+    const firstOfSecond = geom.coordinates[1][0];
+
+    t.ok(
+      Math.abs(Math.abs(lastOfFirst[0]) - 180) < 0.001,
+      "first segment ends at ±180°"
+    );
+    t.ok(
+      Math.abs(Math.abs(firstOfSecond[0]) - 180) < 0.001,
+      "second segment starts at ±180°"
+    );
+    t.ok(
+      Math.abs(lastOfFirst[1] - firstOfSecond[1]) < 0.001,
+      "latitude matches at antimeridian split"
+    );
+
+    t.end();
+  });
+});

packages/turf-great-circle/test/in/antimeridian-auckland-lax.geojson

@@ -0,0 +1,21 @@
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": { "name": "Auckland" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [174.79, -36.85]
+      }
+    },
+    {
+      "type": "Feature",
+      "properties": { "name": "Los Angeles" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [-118.41, 33.94]
+      }
+    }
+  ]
+}

packages/turf-great-circle/test/in/antimeridian-shanghai-sfo.geojson

@@ -0,0 +1,21 @@
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": { "name": "Shanghai" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [121.81, 31.14]
+      }
+    },
+    {
+      "type": "Feature",
+      "properties": { "name": "San Francisco" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [-122.38, 37.62]
+      }
+    }
+  ]
+}

packages/turf-great-circle/test/in/antimeridian-tokyo-lax.geojson

@@ -0,0 +1,21 @@
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "properties": { "name": "Tokyo" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [139.7798, 35.5494]
+      }
+    },
+    {
+      "type": "Feature",
+      "properties": { "name": "Los Angeles" },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [-118.4085, 33.9416]
+      }
+    }
+  ]
+}

packages/turf-great-circle/test/out/antimeridian-auckland-lax.geojson

@@ -0,0 +1,140 @@
+{
+  "type": "FeatureCollection",
+  "features": [
+    {
+      "type": "Feature",
+      "geometry": {
+        "type": "MultiLineString",
+        "coordinates": [
+          [
+            [174.79, -36.85],
+            [175.691979, -36.23329],
+            [176.579765, -35.609916],
+            [177.453753, -34.980132],
+            [178.314335, -34.344181],
+            [179.161902, -33.7023],
+            [179.996841, -33.054717],
+            [180, -33.052238]
+          ],
+          [
+            [-180, -33.052238],
+            [-179.180464, -32.401654],
+            [-178.369634, -31.743323],
+            [-177.570293, -31.079931],
+            [-176.782073, -30.411677],
+            [-176.004608, -29.738754],
+            [-175.237542, -29.061348],
+            [-174.480521, -28.379638],
+            [-173.7332, -27.693799],
+            [-172.995237, -27.003999],
+            [-172.266299, -26.310402],
+            [-171.546059, -25.613163],
+            [-170.834194, -24.912436],
+            [-170.13039, -24.208369],
+            [-169.434337, -23.501103],
+            [-168.745734, -22.790779],
+            [-168.064281, -22.07753],
+            [-167.38969, -21.361486],
+            [-166.721673, -20.642774],
+            [-166.059951, -19.921517],
+            [-165.404251, -19.197834],
+            [-164.754301, -18.471841],
+            [-164.109839, -17.743652],
+            [-163.470605, -17.013375],
+            [-162.836345, -16.281118],
+            [-162.206808, -15.546986],
+            [-161.581749, -14.811081],
+            [-160.960926, -14.073502],
+            [-160.344102, -13.334346],
+            [-159.731042, -12.593709],
+            [-159.121517, -11.851685],
+            [-158.515298, -11.108364],
+            [-157.912163, -10.363837],
+            [-157.31189, -9.618192],
+            [-156.714261, -8.871515],
+            [-156.119059, -8.123892],
+            [-155.526072, -7.375407],
+            [-154.935089, -6.626144],
+            [-154.345899, -5.876184],
+            [-153.758295, -5.125609],
+            [-153.17207, -4.374499],
+            [-152.587021, -3.622933],
+            [-152.002943, -2.870992],
+            [-151.419634, -2.118753],
+            [-150.836891, -1.366295],
+            [-150.254514, -0.613695],
+            [-149.6723, 0.138967],
+            [-149.090048, 0.891616],
+            [-148.507559, 1.644172],
+            [-147.924631, 2.396558],
+            [-147.341061, 3.148697],
+            [-146.756648, 3.900508],
+            [-146.171189, 4.651915],
+            [-145.584479, 5.402837],
+            [-144.996314, 6.153194],
+            [-144.406486, 6.902906],
+            [-143.814787, 7.651892],
+            [-143.221007, 8.400068],
+            [-142.624934, 9.147351],
+            [-142.026353, 9.893657],
+            [-141.425049, 10.6389],
+            [-140.820801, 11.382992],
+            [-140.213388, 12.125845],
+            [-139.602584, 12.867367],
+            [-138.988161, 13.607468],
+            [-138.369888, 14.346053],
+            [-137.747528, 15.083025],
+            [-137.120844, 15.818288],
+            [-136.489592, 16.551739],
+            [-135.853525, 17.283277],
+            [-135.21239, 18.012796],
+            [-134.565932, 18.740187],
+            [-133.91389, 19.46534],
+            [-133.255998, 20.188141],
+            [-132.591984, 20.908472],
+            [-131.921572, 21.626213],
+            [-131.24448, 22.34124],
+            [-130.560422, 23.053425],
+            [-129.869102, 23.762635],
+            [-129.170223, 24.468736],
+            [-128.463479, 25.171587],
+            [-127.748558, 25.871043],
+            [-127.025144, 26.566955],
+            [-126.292912, 27.259169],
+            [-125.551532, 27.947526],
+            [-124.800669, 28.63186],
+            [-124.039979, 29.312001],
+            [-123.269115, 29.987773],
+            [-122.487721, 30.658994],
+            [-121.695437, 31.325475],
+            [-120.891897, 31.987022],
+            [-120.076729, 32.643432],
+            [-119.249557, 33.294497],
+            [-118.41, 33.94]
+          ]
+        ]
+      },
+      "properties": {}
+    },
+    {
+      "type": "Feature",
+      "properties": {
+        "name": "Auckland"
+      },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [174.79, -36.85]
+      }
+    },
+    {
+      "type": "Feature",
+      "properties": {
+        "name": "Los Angeles"
+      },
+      "geometry": {
+        "type": "Point",
+        "coordinates": [-118.41, 33.94]
+      }
+    }
+  ]
+}