Add unit test to confirm change token is disposed during (#53827)

* Add unit test to confirm change token is disposed during
razer hot reload.

* Per Makinnon's feedback, switch to a callback model
to create the wrapped disposable for this unit test.

* Update src/Components/Endpoints/test/HotReloadServiceTests.cs

---------

Co-authored-by: Mackinnon Buck <[email protected]>

Author: jacdavis

src/Components/Endpoints/src/Builder/RazorComponentEndpointDataSource.cs

@@ -28,7 +28,9 @@ internal class RazorComponentEndpointDataSource<[DynamicallyAccessedMembers(Comp
     private List<Endpoint>? _endpoints;
     private CancellationTokenSource _cancellationTokenSource;
     private IChangeToken _changeToken;
-    private IDisposable? _disposable;                   // THREADING: protected by _lock
+    private IDisposable? _disposableChangeToken;   // THREADING: protected by _lock
+
+    public Func<IDisposable, IDisposable> SetDisposableChangeTokenAction = disposableChangeToken => disposableChangeToken;
 
     // Internal for testing.
     internal ComponentApplicationBuilder Builder => _builder;
@@ -144,8 +146,8 @@ private void UpdateEndpoints()
             oldCancellationTokenSource?.Dispose();
             if (_hotReloadService is { MetadataUpdateSupported : true })
             {
-                _disposable?.Dispose();
-                _disposable = ChangeToken.OnChange(_hotReloadService.GetChangeToken, UpdateEndpoints);
+                _disposableChangeToken?.Dispose();
+                _disposableChangeToken = SetDisposableChangeTokenAction(ChangeToken.OnChange(_hotReloadService.GetChangeToken, UpdateEndpoints));
             }
         }
     }
@@ -154,8 +156,8 @@ public void OnHotReloadClearCache(Type[]? types)
     {
         lock (_lock)
         {
-            _disposable?.Dispose();
-            _disposable = null;
+            _disposableChangeToken?.Dispose();
+            _disposableChangeToken = null;
         }
     }
 

src/Components/Endpoints/test/HotReloadServiceTests.cs

@@ -137,6 +137,52 @@ public void NotifiesCompositeEndpointDataSource()
         Assert.Empty(compositeEndpointDataSource.Endpoints);
     }
 
+    private sealed class WrappedChangeTokenDisposable : IDisposable
+    {
+        public bool IsDisposed { get; private set; }
+        private readonly IDisposable _innerDisposable;
+
+        public WrappedChangeTokenDisposable(IDisposable innerDisposable)
+        { 
+            _innerDisposable = innerDisposable;
+        }
+
+        public void Dispose()
+        { 
+             IsDisposed = true;
+             _innerDisposable.Dispose();
+        }
+    }
+
+    [Fact]
+    public void ConfirmChangeTokenDisposedHotReload()
+    {
+        // Arrange
+        var builder = CreateBuilder(typeof(ServerComponent));
+        var services = CreateServices(typeof(MockEndpointProvider));
+        var endpointDataSource = CreateDataSource<App>(builder, services);
+
+        WrappedChangeTokenDisposable wrappedChangeTokenDisposable = null;
+
+        endpointDataSource.SetDisposableChangeTokenAction = (IDisposable disposableChangeToken) => {
+            wrappedChangeTokenDisposable = new WrappedChangeTokenDisposable(disposableChangeToken); 
+            return wrappedChangeTokenDisposable;
+        };
+
+        var endpoint = Assert.IsType<RouteEndpoint>(Assert.Single(endpointDataSource.Endpoints));
+        Assert.Equal("/server", endpoint.RoutePattern.RawText);
+        Assert.DoesNotContain(endpoint.Metadata, (element) => element is TestMetadata);
+
+        // Make a modification and then perform a hot reload.
+        endpointDataSource.Conventions.Add(builder =>
+            builder.Metadata.Add(new TestMetadata()));
+        HotReloadService.UpdateApplication(null);
+        HotReloadService.ClearCache(null);
+
+        // Confirm the change token is disposed after ClearCache
+        Assert.True(wrappedChangeTokenDisposable.IsDisposed);
+    }
+
     private class TestMetadata { }
 
     private ComponentApplicationBuilder CreateBuilder(params Type[] types)