[MGLGeoJSONSource initWithIdentifier:geoJSONData] crashes if data isn't a feature collection

[jfirebaugh]

The following code crashes with the unhandled exception mapbox::util::bad_variant_access: in get<T>() on this line.

    MGLGeoJSONSource *geojsonSource = [[MGLGeoJSONSource alloc]
        initWithIdentifier:@"geojson"
               geoJSONData:[@"{\"type\": \"Point\", \"coordinates\": [0, 0]}" dataUsingEncoding:NSUTF8StringEncoding]
                   options:nil];

[nitrag]

Same error mapbox::util::bad_variant_access: in get<T>() so I figured I'd comment here.

I'm also getting this bug when adding MGLCircleStyleLayer after a MGLGeoJSONSource without any markers (it is only a single line).

var options = [String : Any]()
        options[MGLGeoJSONClusterOption] = true
        options[MGLGeoJSONClusterRadiusOption] = 42
        options[MGLGeoJSONClusterMaximumZoomLevelOption] = 14
        options[MGLGeoJSONMaximumZoomLevelOption] = 20
        options[MGLGeoJSONToleranceOption] = 1
let jsonPath = Bundle.main.url(forResource: "example", withExtension: "geojson")!
let geoJsonSource = MGLGeoJSONSource(identifier: "testasdf", url: jsonPath, options: options)
self.mapView.style().add(geoJsonSource)
NSLog("Source has been created and added")

//comment the rest of this out and it will work
let circleLayer = MGLCircleStyleLayer(identifier: "circle-geojson", source: geoJsonSource)
circleLayer.circleColor = MGLStyleConstantValue(rawValue: UIColor.orange)
circleLayer.circleOpacity = MGLStyleConstantValue(rawValue: 0.8)
circleLayer.circleRadius = MGLStyleConstantValue(rawValue: 13)
self.mapView.style().add(circleLayer);

[nitrag]

I take that back...

It seems to crash when I reuse options. If I set:
let geoJsonSource1 = MGLGeoJSONSource(identifier: "asdfasadfas", url: path, options: [String : Any]())

it works fine. However as like below, it will crash

func addGeoJSONSource(){

    var options = [String : Any]()
    options[MGLGeoJSONClusterOption] = true
    options[MGLGeoJSONClusterRadiusOption] = 42
    options[MGLGeoJSONClusterMaximumZoomLevelOption] = 14
    options[MGLGeoJSONMaximumZoomLevelOption] = 20
    options[MGLGeoJSONToleranceOption] = 1

    let path = Bundle.main.url(forResource: "example", withExtension: "geojson")!
--> let geoJsonSource1 = MGLGeoJSONSource(identifier: "asdfasadfas", url: path, options: options)
    self.mapView.style().add(geoJsonSource1)
    let lineTest = MGLLineStyleLayer(identifier: "line-geojson", source: geoJsonSource1)
    self.mapView.style().add(lineTest)
    NSLog("Source has been created and added")

    let jsonPath = Bundle.main.url(forResource: "mcdonalds", withExtension: "geojson")!
    let geoJsonSource = MGLGeoJSONSource(identifier: "markers", url: jsonPath, options: options)
    self.mapView.style().add(geoJsonSource)
    NSLog("Source has been created and added")

    let circleLayer = MGLCircleStyleLayer(identifier: "circle-geojson", source: geoJsonSource)
    circleLayer.circleColor = MGLStyleConstantValue(rawValue: UIColor.orange)
    circleLayer.circleOpacity = MGLStyleConstantValue(rawValue: 0.8)
    circleLayer.circleRadius = MGLStyleConstantValue(rawValue: 13)
    self.mapView.style().add(circleLayer);

    NSLog("Done adding GeoJSON");
}

`libc++abi.dylib: terminating with uncaught exception of type mapbox::util::bad_variant_access: in get<T>()`

[1ec5]

This line assumes it’s a feature collection without checking first. This initializer should check first and return nil if the data doesn’t contain a feature collection or couldn’t be parsed as GeoJSON for some reason. The initializer’s return type should be declared as nullable instancetype, which will result in a failable initializer in Swift. We also need to document the fact that a feature collection is required.

[jfirebaugh]

Why is a feature collection required? Can we implement full GeoJSON support instead?

[1ec5]

Oh, I was unaware that the style specification allows GeoJSON layers to have any GeoJSON type at the root. MGLGeoJSONStyleLayer should definitely support all of GeoJSON, because any type could come from a preexisting layer in the style.

With that change, features doesn’t make as much sense as an array of MGLFeature instances. I suppose it needs to be feature instead, typed as a (nullable) MGLFeature instance that could be an MGLShapeCollectionFeature under the hood for the cases that don’t currently crash. It’ll be a bit less convenient for use cases such as #6793 (comment), unfortunately.

/cc @boundsj

[frederoni]

Fixed in #7145