Save an empty layer to GeoJSON drop all fields

[qgib]

Author Name: Etienne Trimaille (@Gustry)
Original Redmine Issue: 18370
Affected QGIS version: 3.1(master)
Redmine category:data_provider

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I could replicate this issue on both QGIS 2.18 and 3.1, with Python script and using the UI.

If I create an empty memory layer and if I save to geojson, then all my fields are lost:

The python code shows the problem:

v = QgsVectorLayer('Point?crs=epsg:4326&field=id:integer&field=name:string(20)', 'test', 'memory')
print(v.isValid())
print(v.fields().count())

path = '/tmp/test_geojson.geojson'
QgsVectorFileWriter.writeAsVectorFormat(v, path, 'utf-8', v.crs(), 'GeoJSON')
export_layer = QgsVectorLayer(path, 'exported', 'ogr')
print(export_layer.isValid())
print(export_layer.fields().count())

It will output on both QGIS 2 and 3:

True
2
True
0

I hope it's not some layer/dataset creation option. I looked in the OGR documentation too. Nothing I could notice.

This is an issue because I expect to have the same attribute table.

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• Screen Shot 2018-03-07 at 10.45.18.png (Etienne Trimaille)

[qgib]

Author Name: Etienne Trimaille (@Gustry)

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Well, it seems it's not a bug. Because attributes in GeoJSON are defined at the feature level, not at the layer level. So obviously, if no features, then no attribute table.

[qgib]

Author Name: Nyall Dawson (@nyalldawson)

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• resolution was changed from to invalid
• status_id was changed from Open to Closed