Decorate error object from CLR

[kxs-rgamezdiaz]

Is it possible to add custom properties to the error object that gets caught in js?

Let's say I want to make the following test pass. The idea is to send an "errorCode" property from the CLR.

[TestClass]
public sealed class ScriptEngineExceptionTests
{
    [TestMethod]
    public void ErrorShouldContainProperties()
    {
        Engine engine = new(options =>
        {
            options.CatchClrExceptions();
        });

        engine.SetValue("myClass", new());

        engine.Execute("""
            function main () {
                try {
                    myClass.MethodThatThrows();
                } catch (e) {
                    return JSON.stringify(e);
                }
            }
            """);

        string result = engine.Invoke("main").ToString();

        Assert.AreEqual("{errorCode:'InvalidOperation'}", result);
    }

    public class MyClass()
    {
        public void MethodThatThrows() => throw new InvalidOperationException("This is a test exception.");
    }
}

Right now the Invoke returns an empty object {}.

Thanks!

[lahma]

This feature has landed main, now you can add decorator in options. #2280

[kxs-rgamezdiaz]

Thank you for the quick fix! Seems perfect, but while this is released, I also found a workaround, just in case someone else doesn't want to wait...

Disabling options.CatchClrExceptions(); and doing something like this:

ObjectInstance errorObject = engine.Intrinsics.Error.Construct(fullMessage);
errorObject.Set("message", fullMessage, throwOnError: false);
errorObject.Set("errorCode", errorCode, throwOnError: false);
throw new JavaScriptException(errorObject);

[kxs-rgamezdiaz]

Oh, final question, @lahma. Is this the most optimal way to add a function to an ObjectInstance ?

 JsValue toStringFunction = engine.Evaluate(
     $$"""() => "Error ({{errorCode}}): {{fullMessage}}";""");

 errorObject.Set("toString", toStringFunction, throwOnError: false);

Thank you!

[lahma]

probably not performance-wise as it needs to evaluate things, but as exceptions are... exceptional - I think this is fine. setting a wrapped CLR function will give you the best performance.