[🐛 Bug]: [dotnet] Unable to use wrapped IWebElements from EventFiringWebDriver within Actions

[ZachBergman]

What happened?

We are using EventFiringWebDriver, which returns EventFiringWebElements. In our source, we have an IWebElement wrapping class called WebElementWrapper, which implements IWebElement, IWrapsElement, ILocatable. When using our WebElementWrappers within an Action builder, we get the following exception: "Target element cannot be converted to IWebElementReference".

Our setup...

public interface IWebElementWrapper : IWebElement, IWrapsElement, ILocatable
{
    // Excluded for brevity
}

public class WebElementWrapper : IWebElementWrapper
{
    private IWebElement _webElement;
    public IWebElement WebElement
    {
        get
        {
            if (_webElement == null)
            {
                _webElement = GetWebElement();
            }
            return _webElement;
        }
    }

    public IWebElement WrappedElement => WebElement;

    // Excluded irrelevant content for brevity
}

[TestClass]
public class Tests
{
    [TestMethod]
    public void Test()
    {
        // WebDriver is an EventFiringWebDriver
        new Actions(WebDriver)
            .MoveToElement(WebElementWrapperClassInstance)
            .Click()
            .Build()
            .Perform();
    }
}

It seems the cause of this is the implementation here (shown below with my comments)

// OpenQA.Selenium.Interactions.PointerInputDevice.PointerMoveInteraction
private Dictionary<string, object> ConvertElement()
{
    // this.target is an IWebElement, which doesn't necessarily implement IWebDriverObjectReference
    IWebDriverObjectReference elementReference = this.target as IWebDriverObjectReference;
    if (elementReference == null)
    {
        // We are falling to backup IWrapsElement, however IWrapsElement also does not necessarily implement IWebDriverObjectReference
        IWrapsElement elementWrapper = this.target as IWrapsElement;
        if (elementWrapper != null)
        {
            // In our scenario, since our IWebElement originated from EventFiringWebDriver, it is actually an EventFiringWebElement
            // which does not implement IWebDriverObectReference so it ends up being null here.
            elementReference = elementWrapper.WrappedElement as IWebDriverObjectReference;
        }
    }

    if (elementReference == null)
    {
        throw new ArgumentException("Target element cannot be converted to IWebElementReference");
    }

    Dictionary<string, object> elementDictionary = elementReference.ToDictionary();
    return elementDictionary;
}

In combination with the fact that EventFiringWebDriver issues EventFiringWebElements, which do not implement IWebDriverObjectReference like their WebElement cousins
EventFiringWebElement

private class EventFiringWebElement : ITakesScreenshot, IWebElement, IWrapsElement, IWrapsDriver

WebElement

public class WebElement : IWebElement, IFindsElement, IWrapsDriver, ILocatable, ITakesScreenshot, IWebDriverObjectReference

How can we reproduce the issue?

Use the combination of a WebElementWrapper class as shown, use a EventFiringWebDriver, and use the Actions class as shown.

Relevant log output

System.ArgumentException "Target element cannot be converted to IWebElementReference"

Operating System

Windows 10

Selenium version

4.18.0

What are the browser(s) and version(s) where you see this issue?

Any

What are the browser driver(s) and version(s) where you see this issue?

Any

Are you using Selenium Grid?

No

[github-actions]

@ZachBergman, thank you for creating this issue. We will troubleshoot it as soon as we can.

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Thank you!

[nvborisenko]

@ZachBergman please expand more about

_webElement = GetWebElement();

GetWebElement() return an instance of some class, share its definition.

[RenderMichael]

The IWebElement returned by the EventFiringWebDriver wraps the original element. Since there is another indirection here, I am suspecting the problem here is that the element is wrapped twice over. Looking at the exceptional code path, we only unwrap the element once.

Fixing this should be a matter of traversing up the wrappers. We should be careful not to enter an infinite loop here: it's easy enough for a type that implements both IWebElement and IWrapsElement to have IWebElement WrappedElement => this;. To keep the solution ironclad, we likely need to protect against infinite chains of elements wrapping one another.

[nvborisenko]

Or carefully review our approach for interfaces. What I know: there is an element at remote end, this element is uniquely identified (string ID). At Selenium side we have some type, and the instance of this type should hold element ID. Then it should be absolutely indifferent what interfaces this type implements, but the instance of this type is knowledge keeper.

I suppose it is more "types design issue" rather than "infinite looping while proxying".