fix: DisposeComponentsAsync disposes components while the dispatcher is busy (fixes #1939)

Author: linkdotnet

CHANGELOG.md

@@ -6,6 +6,10 @@ All notable changes to **bUnit** will be documented in this file. The project ad
 
 ## [Unreleased]
 
+### Fixed
+
+- `DisposeComponentsAsync()` could dispose nothing when the renderer's dispatcher was busy, e.g. with a timer calling `InvokeAsync`. Reported by [@xfunc-tim-schneider](https://github.com/xfunc-tim-schneider) in #1939. Fixed by [@linkdotnet](https://github.com/linkdotnet).
+
 ## [2.11.3] - 2026-09-13
 
 ### Fixed

src/bunit/Rendering/BunitRenderer.cs

@@ -281,27 +281,21 @@ public IReadOnlyList<IRenderedComponent<TComponent>> FindComponents<TComponent>(
 	public Task DisposeComponents()
 	{
 		ObjectDisposedException.ThrowIf(disposed, this);
-		Task? returnTask;
 
-		lock (renderTreeUpdateLock)
+		return Dispatcher.InvokeAsync(async () =>
 		{
-			returnTask = Dispatcher.InvokeAsync(async () =>
-			{
-				ResetUnhandledException();
-
-				foreach (var root in rootComponents)
-				{
-					root.Detach();
-				}
-
-				await Task.WhenAll(disposalTasks).ConfigureAwait(false);
-				disposalTasks.Clear();
-			});
+			ResetUnhandledException();
 
+			var roots = rootComponents.ToArray();
 			rootComponents.Clear();
-		}
 
-		return returnTask;
+			foreach (var root in roots)
+			{
+				root.Detach();
+			}
+
+			await Task.WhenAll(disposalTasks.ToArray()).ConfigureAwait(false);
+		});
 	}
 
 	/// <inheritdoc/>
@@ -425,21 +419,11 @@ protected override void AddPendingTask(ComponentState? componentState, Task task
 		if (componentState is null)
 		{
 			ArgumentNullException.ThrowIfNull(task);
-			AddDisposalTaskToQueue();
+			disposalTasks.RemoveAll(static t => t.IsCompleted);
+			disposalTasks.Add(task);
 		}
 
 		base.AddPendingTask(componentState, task);
-
-		void AddDisposalTaskToQueue()
-		{
-			var t = task;
-			t = task.ContinueWith(_ =>
-			{
-				disposalTasks.Remove(t);
-			}, TaskScheduler.Current);
-
-			disposalTasks.Add(t);
-		}
 	}
 
 	internal Task SetDirectParametersAsync<TComponent>(IRenderedComponent<TComponent> renderedComponent, ParameterView parameters)
@@ -602,7 +586,6 @@ protected override void Dispose(bool disposing)
 			if (disposing)
 			{
 				returnedRenderedComponentIds.Clear();
-				disposalTasks.Clear();
 				unhandledExceptionTsc.TrySetCanceled();
 			}
 

tests/bunit.tests/BunitContextTest.cs

@@ -52,6 +52,28 @@ public async Task Test104()
 		callStack.Count.ShouldBe(1);
 	}
 
+	[Fact(DisplayName = "DisposeComponents disposes components while the dispatcher is busy")]
+	public async Task Test105()
+	{
+		var callStack = new List<string>();
+		Render<ChildDispose>(ps => ps.Add(p => p.CallStack, callStack));
+		using var entered = new ManualResetEventSlim();
+		using var release = new ManualResetEventSlim();
+		var blocker = Task.Run(() => Renderer.Dispatcher.InvokeAsync(() =>
+		{
+			entered.Set();
+			release.Wait();
+		}));
+		entered.Wait();
+
+		var disposeTask = DisposeComponentsAsync();
+		release.Set();
+		await disposeTask;
+		await blocker;
+
+		callStack.Count.ShouldBe(1);
+	}
+
 	[Fact(DisplayName = "The test service provider should register a placeholder HttpClient which throws exceptions")]
 	public void Test024()
 	{