UndefinedBindingResult Throws exception when using #String.Equal

[Vfleitao]

Heya

I have a small template that contains lines like this

<a href="/" class="plain text-black {{#String.Equal viewData.page "home" }}active{{/String.Equal}}">Home</a>

When I use the ThrowOnUnresolvedBindingExpression = false HandleBarsConfiguration, the String.Equal still throws an exception with

Object of type 'HandlebarsDotNet.UndefinedBindingResult' cannot be converted to type 'System.String'.

if the viewData.page is an UndefinedBindingResult.

Just doing this works as expected

<a href="/" class="plain text-black {{viewData.page}}">Home</a>

Is this an expected behaviour or am I missing some configuration on the Helpers?

[Vfleitao]

Looking a bit deeper into the ArgumentsParser, I wonder if something like this would not make sense so that if the argument ends up being a an UndefinedBindingResult we return the default value or throw an exception?

public static List<object?> Parse(IHandlebars context, ParameterInfo[] parameters, Arguments arguments)
{
    var result = new List<object?>();
    for (int i = 0; i < parameters.Length; i++)
    {
        if (parameters[i].IsParam())
        {
            result.Add(arguments.Skip(i).ToArray());
        }
        else if (i < arguments.Length)
        {
            result.Add(arguments[i]);
        }
    }

    return result.Select(argument => Parse(context, argument)).ToList();
}

public static object? Parse(IHandlebars context, object? argument, bool convertObjectArrayToStringList = false)
{
    if (argument is UndefinedBindingResult valueAsUndefinedBindingResult)
    {
        if (TryParseUndefinedBindingResult(valueAsUndefinedBindingResult, out var parsedAsObjectList) && convertObjectArrayToStringList)
        {
            return parsedAsObjectList.Cast<string?>().ToList();
        }

        if(context.Configuration.ThrowOnUnresolvedBindingExpression)
        {
            throw new HandlebarsRuntimeException($"The value '{valueAsUndefinedBindingResult.Value}' cannot be converted to a valid type.");
        }

        return valueAsUndefinedBindingResult.Value;
    }

    return argument;
}

[StefH]

I guess the viewData is null or does not have a property named page? What is rendered for this? <a href="/" class="plain text-black {{viewData.page}}">Home</a>

[StefH]

https://github.com/Handlebars-Net/Handlebars.Net.Helpers/pull/95

[Vfleitao]

I guess the viewData is null or does not have a property named page? What is rendered for this? <a href="/" class="plain text-black {{viewData.page}}">Home</a>

In my case, the viewData is literally just set with the null value. It renders <a href="/" class="plain text-black viewData.page">Home</a> since my UnresolvedBindingFormatter is set to "{0}"

[Vfleitao]

95

now this is a quick fix. Thank you very much @StefH