ArgumentOutOfRangeException from Browser.TaskEventLoop

Bug Report

Prerequisites

• Can you reproduce the problem in a MWE?
• Are you running the latest version of AngleSharp?
• ~Did you check the FAQs to see if that helps you?~ don’t see any FAQ in readme/wiki
• Are you reporting to the correct repository? (there are multiple AngleSharp libraries, e.g., AngleSharp.Css for CSS support)
• Did you perform a search in the issues?

~For more information, see the CONTRIBUTING guide.~ no such file

Description

I got following unexpected exception from thread pool during tests debugging:

mscorlib.dll!System.ThrowHelper.ThrowArgumentOutOfRangeException(System.ExceptionArgument argument, System.ExceptionResource resource) Line 93	C#
 	mscorlib.dll!System.ThrowHelper.ThrowArgumentOutOfRangeException() Line 57	C#
 	mscorlib.dll!System.Collections.Generic.List<AngleSharp.Dom.Node>.this[int].get(int index) Line 181	C#
 	AngleSharp.dll!AngleSharp.Dom.NodeList.this[int].get(int index)	Unknown
 	AngleSharp.dll!AngleSharp.Dom.NodeList.AngleSharp.Dom.INodeList.get_Item(int index)	Unknown
 	AngleSharp.dll!AngleSharp.Dom.NodeExtensions.FindChild<AngleSharp.Html.Dom.HtmlHtmlElement>(AngleSharp.Dom.INode parent)	Unknown
 	AngleSharp.dll!AngleSharp.Html.Dom.HtmlDocument.DocumentElement.get()	Unknown
 	AngleSharp.dll!AngleSharp.Dom.Document.Body.get()	Unknown
 	AngleSharp.dll!AngleSharp.Dom.Document.RaiseLoadedEvent()	Unknown
 	AngleSharp.dll!AngleSharp.Browser.EventLoopExtensions.Enqueue.AnonymousMethod__0(System.Threading.CancellationToken c)	Unknown
 	AngleSharp.dll!AngleSharp.Browser.TaskEventLoop.TaskEventLoopEntry.Run.AnonymousMethod__0()	Unknown
 	mscorlib.dll!System.Threading.Tasks.Task.InnerInvoke() Line 2875	C#
 	mscorlib.dll!System.Threading.Tasks.Task.Execute() Line 2499	C#
 	mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) Line 2861	C#
 	mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 955	C#
 	mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 902	C#
 	mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2827	C#
 	mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2757	C#
 	mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() Line 2703	C#
 	mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() Line 820	C#
 	mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() Line 1161	C#
 	[Native to Managed Transition]	

Steps to Reproduce

1. no idea

Expected behavior: no unexpected exceptions and no hidden event loops because I use anglesharp only as HTML/CSS parser and don’t expect any runtime features like event-loop enabled with such scenario

Actual behavior: exception from browser event loop when I don’t use any runtime features - just parser

Environment details: [windows, .net 4.7.1]

Possible Solution

Maybe I didn’t noticed some knob to disable this functionality.

Checking document on stack I see that it is “about:blank” document and failed NodeList is empty. Have no idea from where this code was initiated and why, because my usecase for angle# is just:

_document = new HtmlParser().ParseDocument(markup);
// traverse dom with QuerySelectorAll and replace/update some nodes

[FlorianRappl]

Landed in devel

[FlorianRappl]

The TaskEventLoop will be removed from 0.13. By default, no event loop (sync emission of events) will be used.

In AngleSharp.Js another (optional) event loop will be provided, which allocates a dedicated thread and provides higher performance and reliability.