fix(polygonize): deduplicate segments in planar graph (#3045)

* fix(polygonize): ignore duplicate segments in planar graph

* chore: add contributor to package.json

---------

Co-authored-by: mfedderly <24275386+mfedderly@users.noreply.github.com>

Author: Traksewt

packages/turf-polygonize/lib/Graph.ts

@@ -112,6 +112,11 @@ class Graph {
    * @param {Node} to - Node which ends the Edge
    */
   addEdge(from: Node, to: Node) {
+    // Note: Avoid creating duplicate Edges (#3045). This is done before the Edge constructor call, which modifies the Nodes that are passed in.
+    if (this.edges.get(from)?.has(to)) {
+      return;
+    }
+
     const edge = new Edge(from, to),
       symetricEdge = edge.getSymetric();
 

packages/turf-polygonize/package.json

@@ -5,7 +5,8 @@
   "author": "Turf Authors",
   "contributors": [
     "Nicolas Cisco <@nickcis>",
-    "Denis Carriere <@DenisCarriere>"
+    "Denis Carriere <@DenisCarriere>",
+    "Kenny Sabir <@Traksewt>"
   ],
   "license": "MIT",
   "bugs": {

packages/turf-polygonize/test.ts

@@ -81,6 +81,40 @@ test("turf-polygonize -- input mutation", (t) => {
   t.end();
 });
 
+test("turf-polygonize -- duplicate segment", (t) => {
+  const lines = featureCollection([
+    lineString([
+      [0, 0],
+      [1, 0],
+    ]),
+    lineString([
+      [1, 0],
+      [1, 1],
+    ]),
+    lineString([
+      [1, 1],
+      [0, 1],
+    ]),
+    lineString([
+      [0, 1],
+      [0, 0],
+    ]),
+    // Duplicate boundary segment should not prevent polygonization.
+    lineString([
+      [0, 0],
+      [1, 0],
+    ]),
+  ]);
+
+  const polygonized = polygonize(lines);
+  t.equal(
+    polygonized.features.length,
+    1,
+    "returns one polygon for closed ring with duplicate edge"
+  );
+  t.end();
+});
+
 function colorize(feature, color = "#F00", width = 6) {
   feature.properties["fill"] = color;
   feature.properties["fill-opacity"] = 0.3;