FindElement.Refresh stuck in infinite loop when setting a child's events source to the parent's

Describe the bug If you set a control’s events source to a parent’s, the foreach loop in FindElement.Refresh() will get stuck in an infinite loop.

Steps to reproduce the bug Try this code: XAML:

<local:TestControl x:Name="CustomControl" AutomationProperties.Name="CustomControl">
                    <Button x:Name="Button1" Content="Button"/>
 </local:TestControl>

XAML.CS

namespace MUXControlsTestApp
{
    public sealed class TestControl : ContentControl
    {
        protected override AutomationPeer OnCreateAutomationPeer()
        {
            return new TestControlAutomationPeer(this);
        }
    }

    public sealed class TestControlAutomationPeer : FrameworkElementAutomationPeer
    {
        public TestControlAutomationPeer(TestControl owner) : base(owner){}
        protected override AutomationControlType GetAutomationControlTypeCore()
        {
            return AutomationControlType.Custom;
        }
    }

    [TopLevelTestPage(Name = "Expander")]
    public sealed partial class ExpanderPage : TestPage
    {
        public ExpanderPage()
        {
            this.InitializeComponent();
            var customControlPeer = FrameworkElementAutomationPeer.FromElement(CustomControl);
            var buttonPeer= FrameworkElementAutomationPeer.FromElement(Button1);

            buttonPeer.EventsSource = customControlPeer;
        }
    }
}

Expected behavior

Screenshots

Version Info

NuGet package version:

Windows app type:

UWP	Win32

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop
Xbox
Surface Hub
IoT

Additional context

[chingucoding]

It seems that this is not an issue with the test infra, but rather the underlying framework/library that provides us with the UIObject objects. In the scenario described by @ejserna , the list of descendants seems to be infinite, at some point it keeps containing the same element over and over again. So the only efficient solution I can think of is save the previous element and break the for loop if the previous element is equal to the current item, does that sound reasonable as a workaround?

[eduardoaguacate]

@chingucoding I think that’s a good workaround, at least that’s what @alexhinz and I thought would make sense.