removeSource() throws TypeError via _updateTerrain() when terrain renderer holds stale source reference

[tibotiber]

mapbox-gl-js version

v3.12.0

Browser and version

Chrome Version 152.0.7939.3 (Official Build) dev (arm64)

Expected behavior

removeSource() completes without throwing, or throws before the source is removed (so callers can handle a true failure)

Actual behavior

Source is removed successfully, then _updateTerrain() throws — leaving callers unable to distinguish a real removal failure from this internal bookkeeping error

Calling map.removeSource(sourceId) throws a TypeError: Cannot read properties of undefined (reading 'get') in certain conditions. The throw originates from the internal _updateTerrain() call that runs after this.style.removeSource(e) inside removeSource. By the time the error throws, the source has already been removed from the style, so the error is benign — but it disrupts any code running in the same call stack after removeSource.

Link to the demonstration

No response

Steps to trigger the unexpected behavior

1. Add a GeoJSON source
2. Add a terrain to the map
3. Remove the source — map.removeSource(sourceId) throws

Relevant log output

TypeError: Cannot read properties of undefined (reading 'get')
  at sn.update (mapbox-gl.js)
  at Map._updateTerrain (mapbox-gl.js)
  at Map.removeSource (mapbox-gl.js)

[tibotiber]

Workaround: Check map.getSource(sourceId) in the catch block — if it returns null, the source was removed and the error is safe to swallow.

[mourner]

v3.12.0

Can you please try a more recent version? I have a feeling we fixed something like this already...

[tibotiber]

will do and report back, thanks

[tibotiber]

Tested with v3.26.0 — bug is still present.

Minimal repro (Standard style, globe projection, before first render):

map.on('load', () => {
  map.addSource('mapbox-dem', { type: 'raster-dem', url: 'mapbox://mapbox.mapbox-terrain-dem-v1', tileSize: 512, maxzoom: 14 })
  map.setTerrain({ source: 'mapbox-dem', exaggeration: 1.5 })

  map.addSource('my-source', { type: 'geojson', data: { type: 'FeatureCollection', features: [] } })
  map.removeSource('my-source') // throws: Cannot read properties of undefined (reading 'get')
})

The source is removed before the throw (so checking getSource() in a catch block is a valid workaround), but the internal _updateTerrain() → Terrain#update() still crashes because terrain.properties is uninitialised when called before the first render frame.

[tibotiber]

Tested PR #13705 against 3.26.0 by applying the fix locally: terrain initializes correctly and removeSource() no longer throws.
Thanks @mhayk