Don't reset feature state

src/source/source_cache.js

@@ -217,9 +217,6 @@ class SourceCache extends Evented {
  }
 
  this._cache.reset();
- //Reset the SourceCache when the source has been reloaded. For GeoJSON sources, 
- // the `id` of features is not guaranteed to be identical when updated
- this._state = new SourceFeatureState();
 
  for (const i in this._tiles) {
  if (this._tiles[i].state !== "errored") this._reloadTile(i, 'reloading');

src/style-spec/reference/v8.json

@@ -381,7 +381,7 @@
  "generateId": {
  "type": "boolean",
  "default": false,
- "doc": "Whether to generate ids for the geojson features. When enabled, the `feature.id` property will be auto assigned based on it's index in the `features` array, over-writing any previous values."
+ "doc": "Whether to generate ids for the geojson features. When enabled, the `feature.id` property will be auto assigned based on its index in the `features` array, over-writing any previous values."
  }
  },
  "source_video": {

src/ui/map.js

@@ -1345,11 +1345,10 @@ class Map extends Camera {
  * required.*
  * @param {Object} state A set of key-value pairs. The values should be valid JSON types.
  *
- * This method requires the `feature.id` attribute on data sets. For GeoJSON sources without 
- * feature ids, set the `generateIds` option in the `GeoJSONSourceSpecification` to auto-assign them. This 
- * option assigns ids based on a feature's index in the source data. Changing the feature data using 
- * `map.getSource('some id').setData(..)` resets the cache of feature states and requires the 
- * caller re-apply the state as needed with the updated `id` values.
+ * This method requires the `feature.id` attribute on data sets. For GeoJSON sources without
+ * feature ids, set the `generateIds` option in the `GeoJSONSourceSpecification` to auto-assign them. This
+ * option assigns ids based on a feature's index in the source data. If you change feature data using
+ * `map.getSource('some id').setData(..)`, you may need to re-apply state taking into account updated `id` values.
  */
  setFeatureState(feature: { source: string; sourceLayer?: string; id: string | number; }, state: Object) {
  this.style.setFeatureState(feature, state);