MGLVectorStyleLayer.sourceLayerIdentifier is never optional

[incanus]

Upstream spec issue: mapbox/mapbox-gl-style-spec#547

Vector layer styling doesn't work if the sourceLayerIdentifier isn't specified, even if there is only one data layer in the source and/or it is named just like the source identifier and/or layer identifier.

While we're in here, we could consider a few enhancements:

• Auto-determining single-data-layer source layer names
• A better property name such as sourceDataLayerIdentifier or sourceLayerName to emphasize that sources have data layers that tie to style layers
• KVO-aware source layer querying a là style layer querying in MGLStyle key-value coding compliance #6097

/cc @1ec5 @boundsj

[incanus]

Some background on iOS: #6269 (comment)

[1ec5]

mapbox/mapbox-gl-style-spec#547 (comment) points out that the source layer is never specified for GeoJSON sources. The documentation could clarify the fact that the source layer is required for multilayered vector sources. We could also bring back the sourceLayerIdentifier initializer parameter but leave it nullable for the vector source case.

Auto-determining single-data-layer source layer names

If after mapbox/mapbox-gl-style-spec#547 the style specification continues to carve out an exception for single-layer sources, but mbgl doesn’t automatically use the sole layer in a source, please open a separate issue.

[ericrwolfe]

Was just scratching my head as to why a layer wasn't appearing.

We ought to consider adding an assertion if the source layer referenced by the style layer isn't found.

[1ec5]

Auto-determining single-data-layer source layer names

We ought to consider adding an assertion if the source layer referenced by the style layer isn't found.

Defaulting to the sole source layer should happen at the mbgl level. The SDK currently can neither do that nor assert that a source layer identifier is valid, because mbgl doesn’t expose any information about what constitutes a vector source (#7255), especially not a source baked into the style and obtained through -sourceWithIdentifier: (#6584).

[1ec5]

Moving off a milestone, because further action depends on #7255.

[1ec5]

An interim fix could look like this:

• Document the fact that a style layer identifier is required when working with MGLVectorSource
• When adding an MGLVectorStyleLayer to an MGLMapView, if the source refers to an MGLVectorSource but there’s no style layer identifier, raise an exception

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.