Extend CLR class, or overwrite functionality

[KoalaBear84]

Have a 'LocaleString' class, supplier provided, not sealed. This contains strings in multiple languages with a CultureInfo 'accessor' which is not great in JavaScript.

Example:

LocaleString localeString;
CultureInfo cultureInfo = new("en");
localeString[cultureInfo] = "Text in English";

The problem is a CultureInfo class is not defaultly available, and a hassle to implement, and use in JavaScript. I would like to replace the CultureInfo part with a string, like "en" and make it work.

This is a snippet of the supplier provided code:

public class LocaleString : ICloneable {
	private Dictionary<CultureInfo, string> stringMap;

	public string this[CultureInfo ci] {
		get {
			if (stringMap != null && ci != null && stringMap.ContainsKey(ci)) {
				return stringMap[ci];
			}

			return null;
		}
		set {
			lock (this) {
				if (stringMap == null) {
					stringMap = new Dictionary<CultureInfo, string>();
				}

				stringMap[ci] = value;
			}
		}
	}
}

I've tried overwriting it, with a string 'accessor', but overwriting might not work :)

public class JintLocaleString : LocaleString
{
	public string this[string languageCode]
	{
		get {
			CultureInfo cultureInfo = new(languageCode);

			if (ContainsCulture(cultureInfo)) return base[cultureInfo];

			return null;
		}
		set {
			base[new(languageCode)] = value;
		}
	}
}

And registering it:

jintEngine.SetValue(typeof(LocaleString).FullName, TypeReference.CreateTypeReference(jintEngine, typeof(JintLocaleString)));

This doesn't work. Is there any way this can be overwritten somehow?

[lahma]

How does it not work?

[KoalaBear84]

I called a function in JavaScript on another object which returns a LocaleString instance and tried to access a text through localeString['en'], but that returned "undefined" (but there is a value for it).

Does the jintEngine.SetValue 'replaced' the implementation of the supplier LocaleString with my own JintLocaleString?

I'll do more tests hopefully tomorrow morning.

[lahma]

Depends how your usage looks like. Hard to say. Maybe a failing xUnit test case would help.

[KoalaBear84]

Sorry, I meant monday morning.

This is a full sample to reproduce. What I would like it to change this behavior, but I'm not sure this is possible with Jint. Else it will be hard as I need to 'proxy' all calls to the underlying objects provided by the supplier of the library.

What I get is System.ArgumentException, "Expected string but got Undefined". What I expect is that it would return "English text".

ConsoleApp_20230306_0843_JintReproduce.zip

using Jint;
using Jint.Native;
using Jint.Runtime.Interop;
using System.Globalization;

Engine jintEngine = new();

jintEngine.SetValue(typeof(LocaleString).FullName, TypeReference.CreateTypeReference(jintEngine, typeof(JintLocaleString)));

JsValue testFunction = jintEngine.Execute(
    """
    function test(localeString) {
       return localeString['en'];
    }
    """).GetValue("test");

LocaleString localeString = new();
localeString[new CultureInfo("en")] = "English Text";
localeString[new CultureInfo("nl")] = "Nederlandse tekst";

JsValue jsValue = jintEngine.Invoke(testFunction, localeString);

Console.WriteLine(jsValue.AsString());
Console.ReadKey();

public class JintLocaleString : LocaleString {
    public string this[string languageCode] {
        get {
            CultureInfo cultureInfo = new(languageCode);

            if (ContainsCulture(cultureInfo)) {
                return base[cultureInfo];
            }

            return null;
        }
        set {
            CultureInfo cultureInfo = new(languageCode);

            base[cultureInfo] = value;
        }
    }
}

[Genteure]

Did you meant to pass in JintLocalString?

- LocaleString localeString = new();
+ LocaleString localeString = new JintLocalString();
  localeString[new CultureInfo("en")] = "English Text";
  localeString[new CultureInfo("nl")] = "Nederlandse tekst";

[KoalaBear84]

No, because this was just example code, in the real code the nuget package of the SAAS platform provides the LocaleString, but it looks like the IObjectConverter thing will be the solution.

[Genteure]

I'm guessing what you want is a IObjectConverter.

[Fact]
public void Test()
{
    var engine = new Engine(o => o.AddObjectConverter(new ExternalLocaleStringConverter()));

    engine.SetValue("locale", new ExternalLocaleString());
    Assert.Equal("English", engine.Evaluate("locale['en']").AsString());
    Assert.Equal("Dutch", engine.Evaluate("locale['nl']").AsString());
}

public class ExternalLocaleStringConverter : IObjectConverter
{
    public bool TryConvert(Engine engine, object value, [NotNullWhen(true)] out JsValue result)
    {
        if (value is ExternalLocaleString localeString)
        {
            result = JsValue.FromObject(engine, new ExternalLocaleStringWrapper(localeString));
            return true;
        }
        result = null;
        return false;
    }

    private class ExternalLocaleStringWrapper
    {
        private readonly ExternalLocaleString _externalLocaleString;

        public ExternalLocaleStringWrapper(ExternalLocaleString externalLocaleString)
        {
            _externalLocaleString = externalLocaleString;
        }

        public string this[string arg]
        {
            get
            {
                CultureInfo cultureInfo = new(arg);
                return _externalLocaleString[cultureInfo];
            }
            set
            {
                CultureInfo cultureInfo = new(arg);
                _externalLocaleString[cultureInfo] = value;
            }
        }
    }
}

public class ExternalLocaleString
{
    public string this[CultureInfo arg]
    {
        get => arg.DisplayName;
        set { }
    }
}

[KoalaBear84]

Thanks! If this also works the other way around, then yes.

In the script they can directly call the function of the nuget library provided by the SAAS service, that returns a LocaleString, but that one requires the use of CultureInfo. I would like to provide a method to use a string (languagecode) instead of CultureInfo.

Didn't yet this IObjectConverter and DefaultTypeConverter before, that sounds good. It would be nice if it was on the documentation / front github page.

The only info I found is another discussion:
#1154

I will try this tomorrow or wednesday, dependig on the amount of meetings and other work 😅

[KoalaBear84]

I've got it working! Sadly you cannot cast the external type to the derived class without self copying or any mapper, luckily it's only 1 property now. Many thanks @lahma @Genteure!

Full solution:

using Jint;
using Jint.Native;
using Jint.Runtime.Interop;
using System.Globalization;

Engine jintEngine = new(o => o.AddObjectConverter<LocaleStringToJint>());

JsValue testFunction = jintEngine.Execute(
	"""
        function test(localeString) {
            return localeString['en'];
        }
        """).GetValue("test");

LocaleString localeString = new();
localeString[new CultureInfo("en")] = "English Text";
localeString[new CultureInfo("nl")] = "Nederlandse tekst";

JsValue jsValue = jintEngine.Invoke(testFunction, localeString);

Console.WriteLine(jsValue.AsString());
Console.ReadKey();

public class ExternalLocaleString : LocaleString
{
	private List<CultureInfo> _languages;

	public ExternalLocaleString(LocaleString localeString)
	{
		_languages = localeString.Languages;

		foreach (CultureInfo language in _languages)
		{
			base[language] = localeString[language];
		}
	}

	public string this[string languageCode]
	{
		get {
			CultureInfo cultureInfo = new(languageCode);

			if (ContainsCulture(cultureInfo))
			{
				return base[cultureInfo];
			}

			return null;
		}
		set {
			CultureInfo cultureInfo = new(languageCode);

			base[cultureInfo] = value;
		}
	}
}

public class LocaleStringToJint : IObjectConverter
{
	public bool TryConvert(Engine engine, object value, out JsValue result)
	{
		if (!(value is LocaleString localeString and not ExternalLocaleString))
		{
			result = null;

			return false;
		}

		result = JsValue.FromObject(engine, new ExternalLocaleString(localeString));

		return true;
	}
}