Fix Terrain Lockups in requestTileGeometry due to Promise Handling Inconsistencies

CHANGES.md

@@ -7,6 +7,7 @@
 ##### Fixes :wrench:
 
 - Corrected JSDoc and Typescript definitions that marked optional arguments as required in `Cesium3dTileset.fromIonAssetId` [#11623](https://github.com/CesiumGS/cesium/issues/11623), and `IonImageryProvider.fromAssetId` [#11624](https://github.com/CesiumGS/cesium/issues/11624)
+- Fixed terrain lockups in `requestTileGeometry` by ensuring promise handling aligns with CesiumJS's expectations. [#11630](https://github.com/CesiumGS/cesium/pull/11630)
 
 ### 1.111 - 2023-11-01
 

CONTRIBUTORS.md

@@ -185,6 +185,9 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
   - [Robert Irving](https://github.com/robert-irving-snc)
 - [General Atomics CCRi](https://www.ga-ccri.com/)
   - [matthias-ccri](https://github.com/matthias-ccri)
+- [Terradepth, Inc.](https://www.terradepth.com/)
+  - [Marc Johnson](https://github.com/marcejohnson)
+  - [Jacob Frazer](https://github.com/coderjake91)
 
 ## [Individual CLA](Documentation/Contributors/CLAs/individual-contributor-license-agreement-v1.0.pdf)
 

packages/engine/Source/Core/CesiumTerrainProvider.js

@@ -897,11 +897,29 @@ CesiumTerrainProvider.prototype.requestTileGeometry = function (
 
   if (!defined(layerToUse) && unknownAvailability) {
     // Try again when availability data is ready– Otherwise the tile will be marked as failed and never re-requested
-    return availabilityPromise.then(() =>
-      this.requestTileGeometry(x, y, level, request)
-    );
+    return availabilityPromise.then(() => {
+      // handle promise or undefined return
+      return new Promise((resolve, reject) => {
+        // defer execution to the next event loop
+        setTimeout(() => {
+          const originalResult = this.requestTileGeometry(x, y, level, request);
+          if (originalResult && typeof originalResult.then === "function") {
+            originalResult
+              .then((result) => {
+                resolve(result);
+              })
+              .catch((err) => {
+                reject(err);
+              });
+          } else {
+            // undefined means deferred, wait for the promise to resolve
+            return resolve(this.requestTileGeometry(x, y, level, request));
+          }
+        }, 0); // next tick
+      });
+    });
   }
-
+  // call overridden function below
   return requestTileGeometry(this, x, y, level, layerToUse, request);
 };