sebastienros.jint/Jint/Runtime/Interop/DelegateWrapper.cs

using System.Globalization;
using System.Reflection;
using Jint.Extensions;
using Jint.Native;
using Jint.Native.Function;

#pragma warning disable IL2072
#pragma warning disable IL3050

namespace Jint.Runtime.Interop;

/// <summary>
/// Represents a FunctionInstance wrapper around a CLR method. This is used by user to pass
/// custom methods to the engine.
/// </summary>
internal sealed class DelegateWrapper : Function
{
    private static readonly JsString _name = new JsString("delegate");
    private readonly Delegate _d;
    private readonly bool _delegateContainsParamsArgument;

    public DelegateWrapper(
        Engine engine, Delegate d)
        : base(engine, engine.Realm, _name, FunctionThisMode.Global)
    {
        _d = d;
        _prototype = engine.Realm.Intrinsics.Function.PrototypeObject;

        var parameterInfos = _d.Method.GetParameters();

        _delegateContainsParamsArgument = false;
        foreach (var p in parameterInfos)
        {
            if (Attribute.IsDefined(p, typeof(ParamArrayAttribute)))
            {
                _delegateContainsParamsArgument = true;
                break;
            }
        }
    }

    protected internal override JsValue Call(JsValue thisObject, JsCallArguments arguments)
    {
        var parameterInfos = _d.Method.GetParameters();

#if NETFRAMEWORK
        if (parameterInfos.Length > 0 && parameterInfos[0].ParameterType == typeof(System.Runtime.CompilerServices.Closure))
        {
            var reducedLength = parameterInfos.Length - 1;
            var reducedParameterInfos = new ParameterInfo[reducedLength];
            Array.Copy(parameterInfos, 1, reducedParameterInfos, 0, reducedLength);
            parameterInfos = reducedParameterInfos;
        }
#endif

        int delegateArgumentsCount = parameterInfos.Length;
        int delegateNonParamsArgumentsCount = _delegateContainsParamsArgument ? delegateArgumentsCount - 1 : delegateArgumentsCount;

        int jsArgumentsCount = arguments.Length;
        int jsArgumentsWithoutParamsCount = Math.Min(jsArgumentsCount, delegateNonParamsArgumentsCount);

        var clrTypeConverter = Engine.TypeConverter;
        var valueCoercionType = Engine.Options.Interop.ValueCoercion;
        var parameters = new object?[delegateArgumentsCount];

        // convert non params parameter to expected types
        for (var i = 0; i < jsArgumentsWithoutParamsCount; i++)
        {
            var parameterType = parameterInfos[i].ParameterType;
            var value = arguments[i];
            object? converted;

            if (typeof(JsValue).IsAssignableFrom(parameterType))
            {
                converted = value;
            }
            else if (!ReflectionExtensions.TryConvertViaTypeCoercion(parameterType, valueCoercionType, value, out converted))
            {
                converted = clrTypeConverter.Convert(
                    value.ToObject(),
                    parameterType,
                    CultureInfo.InvariantCulture);
            }

            parameters[i] = converted;
        }

        // assign null to parameters not provided
        for (var i = jsArgumentsWithoutParamsCount; i < delegateNonParamsArgumentsCount; i++)
        {
            if (parameterInfos[i].ParameterType.IsValueType)
            {
                parameters[i] = Activator.CreateInstance(parameterInfos[i].ParameterType);
            }
            else
            {
                parameters[i] = null;
            }
        }

        // assign params to array and converts each object to expected type
        if (_delegateContainsParamsArgument)
        {
            int paramsArgumentIndex = delegateArgumentsCount - 1;
            int paramsCount = Math.Max(0, jsArgumentsCount - delegateNonParamsArgumentsCount);

            var paramsParameterType = parameterInfos[paramsArgumentIndex].ParameterType.GetElementType();
            var paramsParameter = Array.CreateInstance(paramsParameterType!, paramsCount);

            for (var i = paramsArgumentIndex; i < jsArgumentsCount; i++)
            {
                var paramsIndex = i - paramsArgumentIndex;
                var value = arguments[i];
                object? converted;

                if (paramsParameterType == typeof(JsValue))
                {
                    converted = value;
                }
                else if (!ReflectionExtensions.TryConvertViaTypeCoercion(paramsParameterType, valueCoercionType, value, out converted))
                {
                    converted = Engine.TypeConverter.Convert(
                        value.ToObject(),
                        paramsParameterType!,
                        CultureInfo.InvariantCulture);
                }

                paramsParameter.SetValue(converted, paramsIndex);
            }

            parameters[paramsArgumentIndex] = paramsParameter;
        }

        try
        {
            var result = _d.DynamicInvoke(parameters);
            if (!IsAwaitable(result))
            {
                return FromObject(Engine, result);
            }
            return ConvertAwaitableToPromise(Engine, result!);
        }
        catch (TargetInvocationException exception)
        {
            Throw.MeaningfulException(Engine, exception);
            throw;
        }
    }

    private static bool IsAwaitable(object? obj)
    {
        if (obj is null)
        {
            return false;
        }
        if (obj is Task)
        {
            return true;
        }
#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP
        if (obj is ValueTask)
        {
            return true;
        }

        // ValueTask<T> is not derived from ValueTask, so we need to check for it explicitly
        var type = obj.GetType();
        if (!type.IsGenericType)
        {
            return false;
        }

        return type.GetGenericTypeDefinition() == typeof(ValueTask<>);
#else
        return false;
#endif
    }

}