Object must implement IConvertible

[martinbu]

From a technical point of view, I do not understand why exchanging an object directly works but not via a Func. Is this an error in Jint or are there are some technical reasons for that?

var engine = new Jint.Engine();
engine.SetValue("Example", new Example());

engine.Execute("""
    const obj = {
        value: 42
    };

    const res = Example.ExchangeObject(obj); // works
    const res2 = Example.ExchangeObjectViaFunc(() => 3); // works, only to ensure that not Func is the issue
    const res3 = Example.ExchangeObjectViaFunc(() => obj); // does not work, throws 'Object must implement IConvertible'

    """);


class Example()
{
    public T ExchangeObject<T>(T obj)
    {
        return obj;
    }

    public T ExchangeObjectViaFunc<T>(Func<T> objViaFunc)
    {
        return objViaFunc();
    }
}

[lahma]

This is quite exotic use case due to the generic and probably hasn't been tested/implemented. As JS doesn't have generics the type system isn't prepared for such..

[martinbu]

Hmm, do you mean the generic T in the Example class, or that Func is based on generics.
If you mean the T used in the Example class, it does not make any difference if I change to code to object or JsValue:

var engine = new Jint.Engine();
engine.SetValue("Example", new Example());

engine.Execute("""
    const obj = {
        value: 42
    };

    const res = Example.ExchangeObject(obj); // works

    const res2 = Example.ExchangeObjectViaFunc(() => 3); // works, only to ensure that not Func is the issue
    const res3 = Example.ExchangeObjectViaFunc(() => obj); // does not work, throws 'Object must implement IConvertible'

    """);


class Example()
{
    public object ExchangeObject(object obj)
    {
        return obj;
    }

    public object ExchangeObjectViaFunc(Func<object> objViaFunc)
    {
        return objViaFunc();
    }
}

What I do not understand is why it makes a difference if an object is passed directly or is returned by a Func. I both cases the object is passed from js to c#.

[lahma]

OK so generics aren't in play here, Jint probably just gets confused by something.