Fix @turf/buffer types to allow for undefined returns when the inputs result in an invalid geometry (#2613)

* Fix @turf/buffer types to allow for undefined returns when the inputs result in an invalid geometry

* Add changelog entry, since this is technically a break

Author: mfedderly

CHANGELOG.md

@@ -14,6 +14,7 @@
 - [`@turf/union`](union) Accept FeatureCollection for multiple inputs (#2247)
 - [`@turf/difference`](difference) Accept FeatureCollection for multiple inputs (#2247)
 - [`@turf/intersect`](intersect) Accept FeatureCollection for multiple inputs (#2247)
+- [`@turf/buffer`](buffer) Add undefined return for when the geometry is invalid (#2613)
 
 ## 🏅 New Features/Enhancements
 - [`@turf/kinks`](kinks) Move to sweepline-intersections library for performance (#1896)

packages/turf-buffer/index.d.ts

@@ -31,12 +31,12 @@ declare function buffer(
     | MultiPolygon,
   radius?: number,
   options?: Options
-): Feature<Polygon | MultiPolygon>;
+): Feature<Polygon | MultiPolygon> | undefined;
 declare function buffer(
   feature: FeatureCollection<GeometryObject> | GeometryCollection,
   radius?: number,
   options?: Options
-): FeatureCollection<Polygon | MultiPolygon>;
+): FeatureCollection<Polygon | MultiPolygon> | undefined;
 
 export { buffer };
 export default buffer;

packages/turf-buffer/test.ts

@@ -156,6 +156,32 @@ test("turf-buffer - morphological closing", (t) => {
   t.end();
 });
 
+test("turf-buffer - undefined return", (t) => {
+  const poly: GeoJSON.Feature<GeoJSON.Polygon> = {
+    type: "Feature",
+    properties: {},
+    geometry: {
+      type: "Polygon",
+      coordinates: [
+        [
+          [-101.87842323574378, 52.250446362382775],
+          [-101.87842323574378, 49.56446202085259],
+          [-98.29404114999511, 49.56446202085259],
+          [-98.29404114999511, 52.250446362382775],
+          [-101.87842323574378, 52.250446362382775],
+        ],
+      ],
+    },
+  };
+
+  t.equal(
+    buffer(poly, -100000000),
+    undefined,
+    "empty geometry should be undefined if the resulting geometry is invalid"
+  );
+  t.end();
+});
+
 function colorize(feature, color) {
   color = color || "#F00";
   if (feature.properties) {