fix: validate feature services before allocating scene owners

src/app/operations.js

@@ -1,3 +1,4 @@
+import { requireFeatureSource } from '../sources/featureSource.js';
 import { createOverpassFeatureSource } from '../sources/overpassFeatures.js';
 import { createSurfaceServices } from './surfaceServices.js';
 import { createAnnotationResolver } from '../annotations/resolver.js';
@@ -14,16 +15,17 @@ export function createApplicationOperations({ requests, signal, eventTarget }) {
     if (typeof requests?.[name]?.[method] !== 'function')
       throw new TypeError(`Missing application request service: ${name}`);
   }
-  const surface = createSurfaceServices({
+  const features = requireFeatureSource(
-    terrainSource: requests.terrain,
-    signal,
-    eventTarget,
-  });
-  const features =
     requests.features ??
       createOverpassFeatureSource({
         boundarySource: requests.boundaries,
         signal,
+      }),
+  );
+  const surface = createSurfaceServices({
+    terrainSource: requests.terrain,
+    signal,
+    eventTarget,
   });
   const annotationResolver = createAnnotationResolver({
     featureSource: features,

src/app/operations.test.mjs

@@ -163,3 +163,22 @@ test('annotation lookup and cached outlines use the supplied source independentl
     { name: 'AbortError' },
   );
 });
+
+test('invalid feature adapters fail before surface listeners are installed', () => {
+  let installed = 0;
+  assert.throws(
+    () =>
+      createApplicationOperations({
+        signal: new AbortController().signal,
+        requests: { ...requests({ getHeights: async () => [] }), features: {} },
+        eventTarget: {
+          addEventListener() {
+            installed++;
+          },
+          removeEventListener() {},
+        },
+      }),
+    /Missing feature operation/,
+  );
+  assert.equal(installed, 0);
+});