Unable to parse empty GeoJSON FeatureCollection to Datasource

[davidtheclark]

I'm trying to create a Datasource from a GeoJSON file with no features, and Mapnik is saying that it can't parse that valid GeoJSON.

Looks like the error that throws originates here:

mapnik/plugins/input/geojson/geojson_datasource.cpp

Line 279 in abe943c

else throw mapnik::datasource_exception("geojson_datasource: Failed to parse GeoJSON file '" + filename_ + "'");

And through node-mapnik it comes out to me like this: Error: geojson_datasource: Failed to parse GeoJSON file ...

The file I've been trying just looks like this:

{
  "type": "FeatureCollection",
  "features": []
}

cc @mapsam and @jakepruitt, who chatted with me about this.

[artemp]

@davidtheclark - can you share how exactly you're creating a Datasource (parameters), pls ?

Python

>>> ds=mapnik.GeoJSON(file="empty.json")
>>> fs = ds.featureset()
>>> type(fs)
<class 'NoneType'>

mapnik-index

mapnik-index empty.json 
max tree depth:8
split ratio:0.55
processing 'empty.json' as GeoJSON
mapnik-index (GeoJSON) : could not extract bounding boxes from : 'empty.json'
Error: failed to process empty.json

both seems reasonable ^

[davidtheclark]

Ah, it seems to be tied to whether I use cache_features or not.

var mapnik = require('mapnik');
var path = require('path');

mapnik.register_default_input_plugins();

// This throws the error "Error: geojson_datasource: Failed to parse GeoJSON file ..."
var x = new mapnik.Datasource({
  type: 'geojson',
  cache_features: true, // Without this line, though, no error is thrown
  file: path.join(__dirname, './test/fixtures/src/no-features.geojson'),
});

I'm using node-mapnik but filed the issue here because of the origin of the error.

[artemp]

Ok, I see, thanks ^

[artemp]

@davidtheclark - ^

[artemp]

Closing here as it has been fixed ^