transform polygons to LineStrings on KML import

Author: mlc

package.json

@@ -47,6 +47,7 @@
     "@turf/helpers": "7.2.0",
     "@turf/invariant": "7.2.0",
     "@turf/meta": "7.2.0",
+    "@turf/polygon-to-line": "7.2.0",
     "geographiclib-dms": "2.1.1",
     "geographiclib-geodesic": "patch:geographiclib-geodesic@npm%3A2.1.1#~/.yarn/patches/geographiclib-geodesic-npm-2.1.1-2da4df7f31.patch",
     "papaparse": "5.5.3",

src/parseData.ts

@@ -1,12 +1,14 @@
 import { feature, featureCollection, point } from '@turf/helpers';
 import { collectionOf, featureOf, geojsonType } from '@turf/invariant';
+import polygonToLine from '@turf/polygon-to-line';
 import type {
   Feature,
   FeatureCollection,
   GeoJSON,
   Geometry,
   LineString,
   Point,
+  Polygon,
 } from 'geojson';
 import Papa from 'papaparse';
 import { kml } from './togeojson';
@@ -140,11 +142,16 @@ export const parseLineString = async (
       throw new Error('Need exactly one feature');
     }
   }
-  if ((json as GeoJSON).type === 'LineString') {
-    geojsonType(json, 'LineString', 'LineString');
-    return feature(json as LineString);
+  if (
+    (json as GeoJSON).type === 'Polygon' ||
+    (json as GeoJSON).type === 'LineString'
+  ) {
+    json = feature(json as Polygon | LineString);
   }
   if ((json as GeoJSON).type === 'Feature') {
+    if ((json as Feature).geometry.type === 'Polygon') {
+      json = polygonToLine(json as Feature<Polygon>);
+    }
     featureOf(json as Feature<any>, 'LineString', 'Feature');
     return json as Feature<LineString>;
   }

yarn.lock

@@ -2453,6 +2453,18 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@turf/polygon-to-line@npm:7.2.0":
+  version: 7.2.0
+  resolution: "@turf/polygon-to-line@npm:7.2.0"
+  dependencies:
+    "@turf/helpers": "npm:^7.2.0"
+    "@turf/invariant": "npm:^7.2.0"
+    "@types/geojson": "npm:^7946.0.10"
+    tslib: "npm:^2.8.1"
+  checksum: 10c0/b840b218e631a252655d233b2c569607d4d3e8d3715a1eab7d26394e4acc1f325b736837d2a82e5c4f678600b2ddc32004782ed3825ca5b1027dce12a4e4cde9
+  languageName: node
+  linkType: hard
+
 "@types/geojson@npm:7946.0.16, @types/geojson@npm:^7946.0.10":
   version: 7946.0.16
   resolution: "@types/geojson@npm:7946.0.16"
@@ -4905,6 +4917,7 @@ __metadata:
     "@turf/helpers": "npm:7.2.0"
     "@turf/invariant": "npm:7.2.0"
     "@turf/meta": "npm:7.2.0"
+    "@turf/polygon-to-line": "npm:7.2.0"
     "@types/geojson": "npm:7946.0.16"
     "@types/node": "npm:22.16.0"
     "@types/papaparse": "npm:5.3.16"