TaskScheduler_UnobservedTaskException after updating to v20.1.0

[Waexu]

Hello,

I have a WPF project (.NET 9) that worked well with Puppeteer until the latest update to v20.1.0. It still functions correctly, but if an HTML-to-PDF conversion is performed at least once, I get the following exception when closing the app:

A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. (Target closed (Session closed))

In my App.xaml.cs, I have the following code:

public App()
{
	TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
}

private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
{
	MessageBox.Show(e.Exception.Message);
	e.SetObserved();
}

This issue occurs only when the MainWindow has closing logic. Here’s my Window_Closing event handler:

private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
	try
	{
		if (Tabs.Items.Count > 1)
		{
			var CloseWarning = new YesNo("Exit", "Are you sure you want to exit?")
			{
				Owner = this
			};
			CloseWarning.ShowDialog();
			if (!CloseWarning.Selected)
			{
				e.Cancel = true;
			}
		}
	}
	catch (Exception ex)
	{
		MessageBox.Show(ex.Message);
	}
}

However, even this simple closing event also causes the same exception:

private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
	e.Cancel = true;
}

Downgrading to v20.0.5 fixed the issue.

[jorrit]

Same here. Could have been caused by #2824.

The exception loaded in task _closeTaskCompletionSource is only read by WaitForNetworkIdleAsync(), which I do not invoke in my code.

[kblok]

Can anyone see if the revert fixes it?
#2878

[Waexu]

e4b3f3a is not compilable and contains many errors. I'm not familiar with the PuppeteerSharp source code, so I can't really check until I have a compilable commit.