fix(lambda-tiler): do not join layers where ids would be duplicated

packages/lambda-tiler/src/routes/__tests__/tile.style.json.test.ts

@@ -400,4 +400,15 @@ describe('/v1/styles', () => {
     assert.equal(body.sources['basemaps_vector']?.type, 'vector');
     assert.equal(body.layers.length, 2);
   });
+
+  it('should error when joining layers with duplicate ids', async () => {
+    const fakeStyle = { id: 'st_labels', name: 'labels', style: fakeVectorStyleConfig };
+    config.put(fakeStyle);
+    config.put(TileSetAerial);
+
+    const request = mockUrlRequest('/v1/styles/labels.json', `?labels=true`, Api.header);
+    const res = await handler.router.handle(request);
+    assert.equal(res.status, 400, res.statusDescription);
+    assert.equal(res.statusDescription.includes('Background1'), true);
+  });
 });

packages/lambda-tiler/src/routes/tile.style.json.ts

@@ -105,6 +105,15 @@ async function setStyleLabels(req: LambdaHttpRequest<StyleGet>, style: StyleJson
     return;
   }
 
+  const layerId = new Set<string>();
+  for (const l of style.layers) layerId.add(l.id);
+
+  for (const newLayers of labels.style.layers) {
+    if (layerId.has(newLayers.id)) {
+      throw new LambdaHttpResponse(400, 'Cannot merge styles with duplicate layerIds: ' + newLayers.id);
+    }
+  }
+
   if (style.glyphs == null) style.glyphs = labels.style.glyphs;
   if (style.sprite == null) style.sprite = labels.style.sprite;
   if (style.sky == null) style.sky = labels.style.sky;