Add SampleHeightMostDetailed tileset load failure test

Tests/TestCesium3DTileset.cs

@@ -126,4 +126,34 @@ public IEnumerator SampleHeightMostDetailedIndicatesNotSampledForPositionOutside
         Assert.AreEqual(result.longitudeLatitudeHeightPositions[0].y, -33.87100, 1e-12);
         Assert.AreEqual(result.longitudeLatitudeHeightPositions[0].z, 1.0, 1e-12);
     }
+
+    [UnityTest]
+    public IEnumerator SampleHeightMostDetailedFailsIfTilesetFailsToLoad()
+    {
+        GameObject go = new GameObject();
+        go.name = "Invalid";
+        Cesium3DTileset tileset = go.AddComponent<Cesium3DTileset>();
+        tileset.tilesetSource = CesiumDataSource.FromUrl;
+        tileset.url = "http://localhost/notgonnawork";
+
+        Task<CesiumSampleHeightResult> task = tileset.SampleHeightMostDetailed(new double3(151.20972, -33.87100, 1.0));
+
+        yield return new WaitForTask(task);
+
+        CesiumSampleHeightResult result = task.Result;
+        Assert.IsNotNull(result);
+        Assert.IsNotNull(result.longitudeLatitudeHeightPositions);
+        Assert.IsNotNull(result.sampleSuccess);
+        Assert.IsNotNull(result.warnings);
+        Assert.AreEqual(result.longitudeLatitudeHeightPositions.Length, 1);
+        Assert.AreEqual(result.sampleSuccess.Length, 1);
+        Assert.AreEqual(result.warnings.Length, 1);
+
+        Assert.AreEqual(result.sampleSuccess[0], false);
+        Assert.AreEqual(result.longitudeLatitudeHeightPositions[0].x, 151.20972, 1e-12);
+        Assert.AreEqual(result.longitudeLatitudeHeightPositions[0].y, -33.87100, 1e-12);
+        Assert.AreEqual(result.longitudeLatitudeHeightPositions[0].z, 1.0, 1e-12);
+
+        Assert.IsTrue(result.warnings[0].Contains("failed to load"));
+    }
 }

native~/Runtime/src/Cesium3DTilesetImpl.cpp

@@ -412,17 +412,30 @@ Cesium3DTilesetImpl::SampleHeightMostDetailed(
         position.z));
   }
 
-  CesiumAsync::Future<SampleHeightResult> future =
-      this->getTileset()
-          ? this->getTileset()->sampleHeightMostDetailed(positions)
-          : getAsyncSystem().createResolvedFuture(
-                Cesium3DTilesSelection::SampleHeightResult{
-                    std::move(positions),
-                    std::vector<bool>(positions.size(), false),
-                    {"Could not sample heights from tileset because it has not "
-                     "been created."}});
-
-  std::move(future)
+  auto sampleHeights = [this, &positions]() mutable {
+    if (this->getTileset()) {
+      return this->getTileset()
+          ->sampleHeightMostDetailed(positions)
+          .catchImmediately([positions = std::move(positions)](
+                                std::exception&& exception) mutable {
+            std::vector<bool> sampleSuccess(positions.size(), false);
+            return Cesium3DTilesSelection::SampleHeightResult{
+                std::move(positions),
+                std::move(sampleSuccess),
+                {exception.what()}};
+          });
+    } else {
+      std::vector<bool> sampleSuccess(positions.size(), false);
+      return getAsyncSystem().createResolvedFuture(
+          Cesium3DTilesSelection::SampleHeightResult{
+              std::move(positions),
+              std::move(sampleSuccess),
+              {"Could not sample heights from tileset because it has not "
+               "been created."}});
+    }
+  };
+
+  sampleHeights()
       .thenImmediately(
           [promise](Cesium3DTilesSelection::SampleHeightResult&& result) {
             System::Array1<Unity::Mathematics::double3> positions(