Fix race condition causing SymbolBucket isEmpty errors

js/source/vector_tile_worker_source.js

@@ -81,10 +81,27 @@ class VectorTileWorkerSource {
      */
     reloadTile(params, callback) {
         const loaded = this.loaded[params.source],
-            uid = params.uid;
+            uid = params.uid,
+            vtSource = this;
         if (loaded && loaded[uid]) {
             const workerTile = loaded[uid];
-            workerTile.parse(workerTile.vectorTile, this.layerIndex, this.actor, callback);
+
+            if (workerTile.status === 'parsing') {
+                workerTile.reloadCallback = callback;
+            } else if (workerTile.status === 'done') {
+                workerTile.parse(workerTile.vectorTile, this.layerIndex, this.actor, done.bind(workerTile));
+            }
+
+        }
+
+        function done(err, data) {
+            if (this.reloadCallback) {
+                const reloadCallback = this.reloadCallback;
+                delete this.reloadCallback;
+                this.parse(this.vectorTile, vtSource.layerIndex, vtSource.actor, reloadCallback);
+            }
+
+            callback(err, data);
         }
     }
 

js/source/worker_tile.js

@@ -34,10 +34,9 @@ class WorkerTile {
         this.collisionBoxArray = new CollisionBoxArray();
         this.symbolInstancesArray = new SymbolInstancesArray();
         this.symbolQuadsArray = new SymbolQuadsArray();
-        const collisionTile = new CollisionTile(this.angle, this.pitch, this.collisionBoxArray);
         const sourceLayerCoder = new DictionaryCoder(Object.keys(data.layers).sort());
 
-        const featureIndex = new FeatureIndex(this.coord, this.overscaling, collisionTile, data.layers);
+        const featureIndex = new FeatureIndex(this.coord, this.overscaling);
         featureIndex.bucketLayerIDs = {};
 
         const buckets = {};
@@ -103,13 +102,9 @@ class WorkerTile {
             }
         }
 
-        const done = () => {
-            this.status = 'done';
 
-            if (this.redoPlacementAfterDone) {
-                this.redoPlacement(this.angle, this.pitch, null);
-                this.redoPlacementAfterDone = false;
-            }
+        const done = (collisionTile) => {
+            this.status = 'done';
 
             const transferables = [];
             callback(null, {
@@ -132,7 +127,7 @@ class WorkerTile {
         }
 
         if (this.symbolBuckets.length === 0) {
-            return done();
+            return done(new CollisionTile(this.angle, this.pitch, this.collisionBoxArray));
         }
 
         let deps = 0;
@@ -143,16 +138,15 @@ class WorkerTile {
             if (err) return callback(err);
             deps++;
             if (deps === 2) {
-                for (const bucket of this.symbolBuckets) {
-                    // Layers are shared and may have been used by a WorkerTile with a different zoom.
-                    for (const layer of bucket.layers) {
-                        layer.recalculate(this.zoom);
-                    }
+                const collisionTile = new CollisionTile(this.angle, this.pitch, this.collisionBoxArray);
 
+                for (const bucket of this.symbolBuckets) {
+                    recalculateLayers(bucket, this.zoom);
                     bucket.prepare(stacks, icons);
                     bucket.place(collisionTile, this.showCollisionBoxes);
                 }
-                done();
+
+                done(collisionTile);
             }
         };
 
@@ -177,19 +171,15 @@ class WorkerTile {
 
     redoPlacement(angle, pitch, showCollisionBoxes) {
         if (this.status !== 'done') {
-            this.redoPlacementAfterDone = true;
             this.angle = angle;
+            this.pitch = pitch;
             return {};
         }
 
-        const collisionTile = new CollisionTile(angle, pitch, this.collisionBoxArray);
+        const collisionTile = new CollisionTile(this.angle, this.pitch, this.collisionBoxArray);
 
         for (const bucket of this.symbolBuckets) {
-            // Layers are shared and may have been used by a WorkerTile with a different zoom.
-            for (const layer of bucket.layers) {
-                layer.recalculate(this.zoom);
-            }
-
+            recalculateLayers(bucket, this.zoom);
             bucket.place(collisionTile, showCollisionBoxes);
         }
 
@@ -204,6 +194,13 @@ class WorkerTile {
     }
 }
 
+function recalculateLayers(bucket, zoom) {
+    // Layers are shared and may have been used by a WorkerTile with a different zoom.
+    for (const layer of bucket.layers) {
+        layer.recalculate(zoom);
+    }
+}
+
 function serializeBuckets(buckets, transferables) {
     return buckets
         .filter((b) => !b.isEmpty())