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Showing content from https://github.com/AngleSharp/AngleSharp.Js/issues/63 below:

Loading jQuery 2.2.4 causes deadlock · Issue #63 · AngleSharp/AngleSharp.Js · GitHub

Bug Report Prerequisites

Can you reproduce the problem in a MWE?
Are you running the latest version of AngleSharp? AngleSharp v0.13.0
Did you check the FAQs to see if that helps you?
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?

Description

As the title says, loading jQuery 2.2.4 causes a deadlock. I'm using the following source:
https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.js

Steps to Reproduce

var config = Configuration.Default
	.WithRequester(new HttpClientRequester())
	.WithDefaultLoader(new LoaderOptions()
	{
		IsResourceLoadingEnabled = true
	})
	.WithJs()
	.WithEventLoop());

var document = await BrowsingContext.New(config).OpenAsync(r => r.Content(@"
<!DOCTYPE html>
<html>
    <head>
        <script src=""https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.js""></script>
    </head>
    <body>
        The body
    </body>
</html>"));

After investigation, it turns out that the issue comes from setting innerHTML while the document is loading. Here is a simple repro:

var config = Configuration.Default
	.WithRequester(new HttpClientRequester())
	.WithDefaultLoader(new LoaderOptions()
	{
		IsResourceLoadingEnabled = true
	})
	.WithJs()
	.WithEventLoop());

var document = await BrowsingContext.New(config).OpenAsync(r => r.Content(@"
<!DOCTYPE html>
<html>
    <head>
        <script>
            var div = document.createElement('div');
            document.documentElement.appendChild(div).innerHTML = '<span></span>';
        </script>
    </head>
    <body>
        The body
    </body>
</html>"));

Expected behavior: OpenAsync should return the document with the script loaded

Actual behavior: OpenAsync is blocked and does not finish ever

Environment details: .Net Core 3.1

Possible Solution

So, after a bunch of debugging, I found the deadlock happens in AngleSharp.Html.Parser.Dom.HtmlDomBuilder.cs:L141.

After parsing the last html part of the fragment, the tokenizer returns an EndOfFile token and is passed through the following methods:

The End method then sets _waiting = _document.FinishLoadingAsync(); which is causing the deadlock. So, I think the End method should not be called when a fragment is being parsed, but I'm not quite sure where exactly to put the condition. Also, I don't know if there are other cases appart of document fragments which could cause this issue.

Here's what I changed and now jQuery loads correctly.
HtmlDomBuilder.cs:L1511

case HtmlTokenType.EndOfFile:
{
+	if (IsFragmentCase)
+		return;

	CheckBodyOnClosing(token);

	if (_templateModes.Count != 0)
	{
		InTemplate(token);
	}
	else
	{
		End();
	}

	return;
}

Is my thinking correct? Also the changes are to be done in the AngleSharp repo, but I'm posting here because I tought the issue is more related to scripting. Should I open an issue in the AngleSharp repo as well or just a PR is enough?

Awesome project btw 👍

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