Fix EMPTY state and source key handling

src/ol/source/VectorTile.js

@@ -215,17 +215,17 @@ class VectorTile extends UrlTile {
             }
           } else if (loadedZ === sourceZ) {
             const tileUrl = this.tileUrlFunction(sourceTileCoord, pixelRatio, projection);
-            sourceTile = new this.tileClass(sourceTileCoord,
-              tileUrl == undefined ? TileState.EMPTY : TileState.IDLE,
-              tileUrl == undefined ? '' : tileUrl,
+            if (tileUrl !== undefined) {
+              sourceTile = new this.tileClass(sourceTileCoord, TileState.IDLE, tileUrl,
                 this.format_, this.tileLoadFunction);
               sourceTile.extent = sourceTileGrid.getTileCoordExtent(sourceTileCoord);
               sourceTile.projection = projection;
               sourceTile.resolution = sourceTileGrid.getResolution(sourceTileCoord[0]);
               this.sourceTiles_[tileKey] = sourceTile;
-            empty = empty && sourceTile.getState() === TileState.EMPTY;
+              empty = false;
               listen(sourceTile, EventType.CHANGE, this.handleTileChange, this);
               sourceTile.load();
+            }
           } else {
             empty = false;
           }
@@ -312,15 +312,18 @@ class VectorTile extends UrlTile {
    */
   getTile(z, x, y, pixelRatio, projection) {
     const tileCoordKey = getKeyZXY(z, x, y);
+    const key = this.getKey();
+    let tile;
     if (this.tileCache.containsKey(tileCoordKey)) {
-      return (
-        /** @type {!import("../Tile.js").default} */ (this.tileCache.get(tileCoordKey))
-      );
-    } else {
+      tile = /** @type {!import("../Tile.js").default} */ (this.tileCache.get(tileCoordKey));
+      if (tile.key === key) {
+        return tile;
+      }
+    }
     const tileCoord = [z, x, y];
     const urlTileCoord = this.getTileCoordForTileUrlFunction(
       tileCoord, projection);
-      const tile = new VectorRenderTile(
+    const newTile = new VectorRenderTile(
       tileCoord,
       urlTileCoord !== null ? TileState.IDLE : TileState.EMPTY,
       urlTileCoord,
@@ -328,10 +331,15 @@ class VectorTile extends UrlTile {
       this.getSourceTiles.bind(this, pixelRatio, projection),
       this.removeSourceTiles.bind(this));
 
-      tile.key = this.getRevision().toString();
-      this.tileCache.set(tileCoordKey, tile);
-      return tile;
+    newTile.key = key;
+    if (tile) {
+      newTile.interimTile = tile;
+      newTile.refreshInterimChain();
+      this.tileCache.replace(tileCoordKey, newTile);
+    } else {
+      this.tileCache.set(tileCoordKey, newTile);
     }
+    return newTile;
   }
 
   /**

test/spec/ol/source/vectortile.test.js

@@ -38,17 +38,21 @@ describe('ol.source.VectorTile', function() {
   });
 
   describe('#getTile()', function() {
+
     it('creates a tile with the correct tile class', function() {
       tile = source.getTile(0, 0, 0, 1, getProjection('EPSG:3857'));
       expect(tile).to.be.a(VectorRenderTile);
     });
+
     it('sets the correct tileCoord on the created tile', function() {
       expect(tile.getTileCoord()).to.eql([0, 0, 0]);
     });
+
     it('fetches tile from cache when requested again', function() {
       expect(source.getTile(0, 0, 0, 1, getProjection('EPSG:3857')))
         .to.equal(tile);
     });
+
     it('loads source tiles', function(done) {
       const source = new VectorTileSource({
         format: new GeoJSON(),
@@ -67,6 +71,32 @@ describe('ol.source.VectorTile', function() {
       });
     });
 
+    it('handles empty tiles tiles', function(done) {
+      const source = new VectorTileSource({
+        format: new GeoJSON(),
+        url: ''
+      });
+      const tile = source.getTile(0, 0, 0, 1, source.getProjection());
+
+      const key = listen(tile, 'change', function(e) {
+        unlistenByKey(key);
+        expect(tile.getState()).to.be(TileState.EMPTY);
+        done();
+      });
+      tile.load();
+    });
+
+    it('creates new tile when source key changes', function() {
+      source.setKey('key1');
+      const tile1 = source.getTile(0, 0, 0, 1, getProjection('EPSG:3857'));
+      const tile2 = source.getTile(0, 0, 0, 1, getProjection('EPSG:3857'));
+      source.setKey('key2');
+      const tile3 = source.getTile(0, 0, 0, 1, getProjection('EPSG:3857'));
+      expect(tile1).to.equal(tile2);
+      expect(tile1.key).to.be('key1');
+      expect(tile3.key).to.be('key2');
+    });
+
   });
 
   describe('#getTileGridForProjection', function() {