Fix weak reference handling in runtime object map (#334)

src/NodeApi/Interop/JSRuntimeContext.cs

@@ -371,11 +371,10 @@ private JSValue GetOrCreateObjectWrapper<T>(T obj, Func<JSValue> createWrapper)
         if (_objectMap.TryGetValue(obj, out JSReference? wrapperWeakRef) &&
             !wrapperWeakRef.IsDisposed)
         {
-            JSValue? existingWrapper = wrapperWeakRef.GetValue();
-            if (existingWrapper.HasValue)
+            if (wrapperWeakRef.TryGetValue(out JSValue existingWrapper))
             {
                 // Return the JS wrapper that was found in the map.
-                return existingWrapper.Value;
+                return existingWrapper;
             }
             else
             {

test/TestCases/napi-dotnet/object_map.js

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+// Test the JSRuntimeContext "object map" which keeps track of JS wrapper objects
+// for corresponding .NET objects.
+
+const assert = require('assert');
+
+/** @type {import('./napi-dotnet')} */
+const binding = require('../common').binding;
+
+const ComplexTypes = binding.ComplexTypes;
+assert.strictEqual(typeof ComplexTypes, 'object');
+
+let obj1 = ComplexTypes.classObject;
+assert(obj1);
+
+// The same JS wrapper instance should be returned every time.
+let obj2 = ComplexTypes.classObject;
+assert.strictEqual(obj1, obj2);
+
+// Force the JS wrapper object to be collected.
+obj1 = obj2 = undefined;
+global.gc();
+
+// A new JS wrapper object should be created.
+let obj3 = ComplexTypes.classObject;
+assert(obj3);