fix: better handling of disposed event handlers with bubbling events

fixes #518 and #517.

Author: egil

src/bunit.core/Rendering/TestRenderer.cs

@@ -80,11 +80,7 @@ public IRenderedComponentBase<TComponent> RenderComponent<TComponent>(ComponentP
 				}
 				catch (ArgumentException ex) when (string.Equals(ex.Message, $"There is no event handler associated with this event. EventId: '{eventHandlerId}'. (Parameter 'eventHandlerId')", StringComparison.Ordinal))
 				{
-					var betterExceptionMsg = new ArgumentException($"There is no event handler with ID '{eventHandlerId}' associated with the '{fieldInfo.FieldValue}' event " +
-						"in the current render tree. This can happen, for example, when using cut.FindAll(), and calling event trigger methods " +
-						"on the found elements after a re-render of the render tree. The workaround is to use re-issue the cut.FindAll() after " +
-						"each render of a component, this ensures you have the latest version of the render tree and DOM tree available in your test code.", ex);
-
+					var betterExceptionMsg = new UnknownEventHandlerIdException(eventHandlerId, fieldInfo, ex);
 					return Task.FromException(betterExceptionMsg);
 				}
 			});

src/bunit.core/Rendering/UnknownEventHandlerIdException.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Runtime.Serialization;
+using Microsoft.AspNetCore.Components.RenderTree;
+
+namespace Bunit.Rendering
+{
+	/// <summary>
+	/// Represents an exception that is thrown when the Blazor <see cref="Renderer"/>
+	/// does not have any event handler with the specified a given ID.
+	/// </summary>
+	[Serializable]
+	public sealed class UnknownEventHandlerIdException : Exception
+	{
+		/// <summary>
+		/// Initializes a new instance of the <see cref="UnknownEventHandlerIdException"/> class.
+		/// </summary>
+		public UnknownEventHandlerIdException(ulong eventHandlerId, EventFieldInfo fieldInfo, Exception innerException)
+			: base(CreateMessage(eventHandlerId, fieldInfo), innerException)
+		{
+		}
+
+		private UnknownEventHandlerIdException(SerializationInfo serializationInfo, StreamingContext streamingContext)
+			: base(serializationInfo, streamingContext) { }
+
+		private static string CreateMessage(ulong eventHandlerId, EventFieldInfo fieldInfo)
+			=> $"There is no event handler with ID '{eventHandlerId}' associated with the '{fieldInfo.FieldValue}' event " +
+				"in the current render tree. This can happen, for example, when using cut.FindAll(), and calling event trigger methods " +
+				"on the found elements after a re-render of the render tree. The workaround is to use re-issue the cut.FindAll() after " +
+				"each render of a component, this ensures you have the latest version of the render tree and DOM tree available in your test code.";
+	}
+}

src/bunit.web/EventDispatchExtensions/TriggerEventDispatchExtensions.cs

@@ -61,25 +61,34 @@ private static Task TriggerBubblingEventAsync(ITestRenderer renderer, IElement e
 		{
 			var eventAttrName = Htmlizer.ToBlazorAttribute(eventName);
 			var eventStopPropergationAttrName = $"{eventAttrName}:stoppropagation";
-			var eventIds = new List<ulong>();
+			var eventTasks = new List<Task>();
 
 			foreach (var candidate in element.GetParentsAndSelf())
 			{
 				if (candidate.TryGetEventId(eventAttrName, out var id))
-					eventIds.Add(id);
+				{
+					try
+					{
+						var info = new EventFieldInfo() { FieldValue = eventName };
+						eventTasks.Add(renderer.DispatchEventAsync(id, info, eventArgs));
+					}
+					catch (UnknownEventHandlerIdException) when (eventTasks.Count > 0)
+					{
+						// Capture and ignore NoEventHandlerException for bubbling events
+						// if at least one event handler has been triggered without throwing.
+					}
+				}
 
 				if (candidate.HasAttribute(eventStopPropergationAttrName) || candidate.EventIsDisabled(eventName))
 				{
 					break;
 				}
 			}
 
-			if (eventIds.Count == 0)
+			if (eventTasks.Count == 0)
 				throw new MissingEventHandlerException(element, eventName);
 
-			var triggerTasks = eventIds.Select(id => renderer.DispatchEventAsync(id, new EventFieldInfo() { FieldValue = eventName }, eventArgs));
-
-			return Task.WhenAll(triggerTasks.ToArray());
+			return Task.WhenAll(eventTasks);
 		}
 
 		private static Task TriggerNonBubblingEventAsync(ITestRenderer renderer, IElement element, string eventName, EventArgs eventArgs)

tests/bunit.testassets/SampleComponents/BubbleEventsRemoveTriggers.razor

@@ -0,0 +1,13 @@
+<div @onclick="() => TopDivClicked = true">
+@if (!BtnClicked)
+{
+	<div @onclick="() => MiddleDivClicked = true">
+		<button @onclick="() => BtnClicked = true">Click me!</button>
+	</div>
+}
+</div>
+@code {
+	public bool BtnClicked { get; private set; } = false;
+	public bool MiddleDivClicked { get; private set; } = false;
+	public bool TopDivClicked { get; private set; } = false;
+}

tests/bunit.testassets/SampleComponents/BubbleEventsThrows.razor

@@ -0,0 +1,19 @@
+<div @onclick="() => TopDivClicked = true">
+	<div @onclick=@MiddleDivHandler>
+		<button @onclick="() => BtnClicked = true">Click me!</button>
+	</div>
+</div>
+
+<p>@BtnClicked</p>
+<p>@MiddleDivClicked</p>
+<p>@TopDivClicked</p>
+
+@code {
+	[Parameter] public string ExceptionMessage { get; set; }
+
+	public bool BtnClicked { get; private set; } = false;
+	public bool MiddleDivClicked { get; private set; } = false;
+	public bool TopDivClicked { get; private set; } = false;
+
+	private void MiddleDivHandler() => throw new Exception(ExceptionMessage);
+}

tests/bunit.testassets/SampleComponents/ClickRemovesEventHandler.razor

@@ -0,0 +1,9 @@
+<button id="first" @onclick="() => visible = false"></button>
+@if (visible)
+{
+	<button id="second" @onclick="() => SecondButtonClicked = true"></button>	
+}
+@code {
+	private bool visible = true;
+	public bool SecondButtonClicked { get; private set; }
+}

tests/bunit.testassets/SampleComponents/EventHandlerThrows.razor

@@ -0,0 +1,5 @@
+<button @onclick="Handler"></button>
+@code {
+	[Parameter] public string ExceptionMessage { get; set; }
+	private void Handler() => throw new Exception(ExceptionMessage);
+}

tests/bunit.web.tests/EventDispatchExtensions/GeneralEventDispatchExtensionsTest.cs

@@ -1,8 +1,10 @@
 using System;
+using System.Linq;
 using System.Reflection;
 using System.Threading.Tasks;
 using AngleSharp;
 using AngleSharp.Dom;
+using AutoFixture.Xunit2;
 using Bunit.Rendering;
 using Bunit.TestAssets.SampleComponents;
 using Moq;
@@ -175,18 +177,6 @@ public async Task Test114(
 			cut.Instance.GrandParentTriggerCount.ShouldBe(1);
 		}
 
-
-		[Fact(DisplayName = "TriggerEventAsync throws when invoked with an unknown event handler ID")]
-		public void Test115()
-		{
-			var eventName = "onclick";
-			var cut = RenderComponent<Wrapper>(ps => ps.AddChildContent("<div />"));
-			var div = cut.Find("div");
-			div.SetAttribute(Htmlizer.ToBlazorAttribute(eventName), "42");
-
-			Should.Throw<ArgumentException>(() => div.TriggerEventAsync(eventName, EventArgs.Empty));
-		}
-
 #if NET6_0_OR_GREATER
 		[Fact(DisplayName = "TriggerEvent can trigger custom events")]
 		public void Test201()
@@ -202,5 +192,54 @@ public void Test201()
 cut.Find("p:last-child").MarkupMatches("<p>You pasted: FOO</p>");
 		}
 #endif
+
+		[Fact(DisplayName = "TriggerEventAsync throws NoEventHandlerException when invoked with an unknown event handler ID")]
+		public void Test300()
+		{
+			var cut = RenderComponent<ClickRemovesEventHandler>();
+			var buttons = cut.FindAll("button");
+			buttons[0].Click();
+
+			Should.Throw<UnknownEventHandlerIdException>(() => buttons[1].Click());
+		}
+
+		[Fact(DisplayName = "Removed bubbled event handled NoEventHandlerException are ignored")]
+		public void Test301()
+		{
+			var cut = RenderComponent<BubbleEventsRemoveTriggers>();
+
+			cut.Find("button").Click();
+
+			// When middle div clicked event handlers is disposed, the
+			// NoEventHandlerException is ignored and the top div clicked event
+			// handler is still invoked.
+			cut.Instance.BtnClicked.ShouldBeTrue();
+			cut.Instance.MiddleDivClicked.ShouldBeFalse();
+			cut.Instance.TopDivClicked.ShouldBeTrue();
+		}
+
+		[Theory(DisplayName = "When bubbling event throws, no other event handlers are triggered")]
+		[AutoData]
+		public void Test302(string exceptionMessage)
+		{
+			var cut = RenderComponent<BubbleEventsThrows>(ps => ps.Add(p => p.ExceptionMessage, exceptionMessage));
+
+			Should.Throw<Exception>(() => cut.Find("button").Click())
+				.Message.ShouldBe(exceptionMessage);
+
+			cut.Instance.BtnClicked.ShouldBeTrue();
+			cut.Instance.MiddleDivClicked.ShouldBeFalse();
+			cut.Instance.TopDivClicked.ShouldBeFalse();
+		}
+
+		[Theory(DisplayName = "When event handler throws, the exception is passed up to test")]
+		[AutoData]
+		public void Test303(string exceptionMessage)
+		{
+			var cut = RenderComponent<EventHandlerThrows>(ps => ps.Add(p => p.ExceptionMessage, exceptionMessage));
+
+			Should.Throw<Exception>(() => cut.Find("button").Click())
+				.Message.ShouldBe(exceptionMessage);
+		}
 	}
 }