turf.convex ignores given properties

[kareemjeiroudi]

Background

In my sample code below, the function combines a list of adjacent polygons into one. Every polygon shows its cadastral information such as cadastral community number, as well as plot number. When combining these polygons into a single convex, I want to combine the numbers into list, that is populated in the convex additional properties. The function seems to ignore the given properties though. Please observe the source code of the convex function.

I would like to open a pull request to fix this problem. I just need approval or confirmation from someone that they were able to reproduce the problem.

• The version of Turf you are using, and any other relevant versions.
  6.5.0
• GeoJSON data as a gist file or geojson.io (filename extension must be .geojson).
  Issue is rather simple, and doesn't need test data. Should be reproducible with any GeoJSON.
• Snippet of source code or for complex examples use jsfiddle.

type AdditionalProperties = {
  cadastralCommunity: string[];
  plots: string[];
};

type TurfFeature = turf.Feature<turf.Polygon | turf.MultiPolygon, AdditionalProperties>;

function combinePolygons(polygons: TurfFeature[]) {
  const combinedPolygons = polygons.reduce<TurfFeature>((previousPolygon, currentPolygon) => {
    if (previousPolygon == null) {
      return currentPolygon;
    }

    const reducedPlotNumbers = [...previousPolygon.properties.plots, ...currentPolygon.properties.plots];
    const reducedCadastralCommunities = [
      ...previousPolygon.properties.cadastralCommunity,
      ...currentPolygon.properties.cadastralCommunity,
    ];

    return turf.union<AdditionalProperties>(previousPolygon, currentPolygon, {
      properties: {
        plots: reducedPlotNumbers,
        cadastralCommunity: reducedCadastralCommunities,
      },
    });
  }, null);

  if (combinedPolygons.geometry.type === 'Polygon') {
    return combinedPolygons;
  }

  const { properties } = combinedPolygons;
  const combinedConvex = turf.convex<AdditionalProperties>(combinedPolygons.geometry, {
    // there's a bug in the convex function where the properties are not populated https://github.com/Turfjs/turf/blob/master/packages/turf-convex/index.ts
     properties: combinedPolygons.properties
  });

  if (combinedConvex) {
    // this should not be necessary
    combinedConvex.properties = properties;
  }

  return combinedConvex;
}

• Verify this issue hasn't already been reported, or resolved in the latest alpha pre-release.
  I couldn't find an issue matching this reported issue.

[smallsaucepan]

Yeah. Wow. That is definitely a bug. Thanks for reporting this @kareemjeiroudi.

Please go ahead and submit a PR 👍

[kareemjeiroudi]

Just opened a PR to resolve this issue. Please let me know if the PR needs improvement or if missing additional information.
#2765