Stackoverflow when using ReplaceChild

[enkelmedia]

I just upgraded the dependency on html-agility-pack from an older version to 1.11.52 and suddenly started to get Stack overflow exceptions.

1. Description

The problem happens in a couple of areas that I have identified.

Using ReplaceChild (when replaced node has already been added to something else)

wrapperDivNode.ChildNodes.Add(nestedTable);
node.ParentNode.ReplaceChild(wrapperDivNode, nestedTable);

(details below)

and:

node.Attributes.RemoveAll();

The workaround here was to just iterate a new list and remove:

 foreach (var attr in node.Attributes.ToList())
 {
     node.Attributes.Remove(attr);
 }

There is a sample of the problem:

var tables = doc.DocumentNode.SelectNodes("//table");

if (tables != null && tables.Any())
{
    
    foreach (var table in tables)
    {
        var nestedTable = table;
        
        if (nestedTable != null)
        {
            // Wrap the table in a div "table-wrapper" so that we can apply "mobile table"-css.
            var wrapperDivNode = HtmlNode.CreateNode("<div class=\"table-wrapper\"></div>");

            wrapperDivNode.ChildNodes.Add(nestedTable);

            nestedTable.ParentNode.ReplaceChild(wrapperDivNode, nestedTable);

        }
        
    }
}

2. Exception

Could not get a good stack trace because of the stack overflow.

3. Fiddle or Project

Error:
https://dotnetfiddle.net/YJJ2jq

Moving the "ReplaceChild" before the "ChildNodes.Add" makes it work:
https://dotnetfiddle.net/sJCUmN

This used to work in older versions and it might be fair that it does not work but there should be a better exception and not a stack overflow.

Works:

4. Any further technical details

Add any relevant detail can help us, such as:

• HAP version:
• NET version Framework 4.7.2

[JonathanMagnan]

Hello @enkelmedia ,

Thank you for the project. My developer will look at it.

Best Regards,

Jon

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[JonathanMagnan]

Hello @enkelmedia ,

A custom exception pointing to this issue has been added in the v1.11.53

The issue was caused because the ChildNodes of a Child contained the same list of ChildNodes as his parent, which led to a stack overflow exception. See this part:

html-agility-pack/src/HtmlAgilityPack.Shared/HtmlNode.cs

Lines 1003 to 1016 in 7c35d8f

	public void SetChildNodesId(HtmlNode chilNode)
	{
	foreach (HtmlNode child in chilNode.ChildNodes)
	{
	_ownerdocument.SetIdForNode(child, child.GetId());
	if (child.ChildNodes == chilNode.ChildNodes)
	{
	throw new Exception("Oops! a scenario that will cause a Stack Overflow has been found. See the following issue for an example: https://github.com/zzzprojects/html-agility-pack/issues/513");
	}
	SetChildNodesId(child);
	}
	}

Another way to make it work is to clone the current node that you want to replace and use it:

if (tables != null && tables.Any())
{
	foreach (var table in tables)
	{
		var nestedTable = table.Clone();

		// Wrap the table in a div "table-wrapper" so that we can apply "mobile table"-css.
		var wrapperDivNode = HtmlNode.CreateNode("<div class=\"table-wrapper\"></div>");

		wrapperDivNode.ChildNodes.Add(nestedTable);

		table.ParentNode.ReplaceChild(wrapperDivNode, table);
	}
}

Let me know if everything is fine for you or there is something else related to this issue.

Best Regards,

Jon

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