sebastienros.jint/Jint/Runtime/Interop/Reflection/IndexerAccessor.cs

using System.Collections;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Reflection;
using Jint.Native;
using Jint.Runtime.Descriptors;
using Jint.Runtime.Descriptors.Specialized;

#pragma warning disable IL2067

namespace Jint.Runtime.Interop.Reflection;

internal sealed class IndexerAccessor : ReflectionAccessor
{
    private readonly object _key;

    internal readonly PropertyInfo _indexer;
    private readonly MethodInfo? _getter;
    private readonly MethodInfo? _setter;
    private readonly MethodInfo? _containsKey;

    private IndexerAccessor(PropertyInfo indexer, MethodInfo? containsKey, object key) : base(indexer.PropertyType)
    {
        _indexer = indexer;
        _containsKey = containsKey;
        _key = key;

        _getter = indexer.GetGetMethod();
        _setter = indexer.GetSetMethod();
    }

    internal static bool TryFindIndexer(
        Engine engine,
        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.PublicProperties)] Type targetType,
        string propertyName,
        [NotNullWhen(true)] out IndexerAccessor? indexerAccessor,
        [NotNullWhen(true)] out PropertyInfo? indexer)
    {
        indexerAccessor = null;
        indexer = null;
        var paramTypeArray = new Type[1];

        // integer keys can be ambiguous as we only know string keys
        int? integerKey = null;

        if (int.TryParse(propertyName, NumberStyles.Integer, CultureInfo.InvariantCulture, out var intKeyTemp))
        {
            integerKey = intKeyTemp;
        }

        IndexerAccessor? ComposeIndexerFactory(PropertyInfo candidate, Type paramType)
        {
            object? key = null;
            // int key is quite common case
            if (paramType == typeof(int) && integerKey is not null)
            {
                key = integerKey;
            }
            else
            {
                engine.TypeConverter.TryConvert(propertyName, paramType, CultureInfo.InvariantCulture, out key);
            }

            if (key is not null)
            {
                // the key can be converted for this indexer
                var indexerProperty = candidate;
                // get contains key method to avoid index exception being thrown in dictionaries
                paramTypeArray[0] = paramType;
                var containsKeyMethod = targetType.GetMethod(nameof(IDictionary<string, string>.ContainsKey), paramTypeArray);
                if (containsKeyMethod is null && targetType.IsAssignableFrom(typeof(IDictionary)))
                {
                    paramTypeArray[0] = typeof(object);
                    containsKeyMethod = targetType.GetMethod(nameof(IDictionary.Contains), paramTypeArray);
                }

                return new IndexerAccessor(indexerProperty, containsKeyMethod, key);
            }

            // the key type doesn't work for this indexer
            return null;
        }

        var filter = new Func<MemberInfo, bool>(m => engine.Options.Interop.TypeResolver.Filter(engine, m));

        // default indexer wins
        var descriptor = TypeDescriptor.Get(targetType);
        if (descriptor.IntegerIndexerProperty is not null && filter(descriptor.IntegerIndexerProperty))
        {
            indexerAccessor = ComposeIndexerFactory(descriptor.IntegerIndexerProperty, typeof(int));
            if (indexerAccessor != null)
            {
                indexer = descriptor.IntegerIndexerProperty;
                return true;
            }
        }

        // try to find first indexer having either public getter or setter with matching argument type
        PropertyInfo? fallbackIndexer = null;
        foreach (var candidate in targetType.GetProperties())
        {
            if (!filter(candidate))
            {
                continue;
            }

            var indexParameters = candidate.GetIndexParameters();
            if (indexParameters.Length != 1)
            {
                continue;
            }

            if (candidate.GetGetMethod() != null || candidate.GetSetMethod() != null)
            {
                var paramType = indexParameters[0].ParameterType;
                indexerAccessor = ComposeIndexerFactory(candidate, paramType);
                if (indexerAccessor != null)
                {
                    if (paramType != typeof(string) ||  integerKey is null)
                    {
                        // exact match, we don't need to check for integer key
                        indexer = candidate;
                        return true;
                    }

                    if (fallbackIndexer is null)
                    {
                        // our fallback
                        fallbackIndexer = candidate;
                    }
                }
            }
        }

        if (fallbackIndexer is not null)
        {
            indexer = fallbackIndexer;
            // just to keep compiler happy, we know we have a value
            indexerAccessor ??= new IndexerAccessor(indexer, containsKey: null, key: null!);
            return true;
        }

        indexerAccessor = default;
        indexer = default;
        return false;
    }

    public override bool Readable => _indexer.CanRead;

    public override bool Writable => _indexer.CanWrite;

    protected override object? DoGetValue(object target, string memberName)
    {
        if (_getter is null)
        {
            ExceptionHelper.ThrowInvalidOperationException("Indexer has no public getter.");
            return null;
        }

        object[] parameters = { _key };

        if (_containsKey != null)
        {
            if (_containsKey.Invoke(target, parameters) as bool? != true)
            {
                return JsValue.Undefined;
            }
        }

        try
        {
            return _getter.Invoke(target, parameters);
        }
        catch (TargetInvocationException tie) when (tie.InnerException is KeyNotFoundException)
        {
            return JsValue.Undefined;
        }
    }

    protected override void DoSetValue(object target, string memberName, object? value)
    {
        if (_setter is null)
        {
            ExceptionHelper.ThrowInvalidOperationException("Indexer has no public setter.");
        }

        object?[] parameters = { _key, value };
        _setter.Invoke(target, parameters);
    }

    public override PropertyDescriptor CreatePropertyDescriptor(Engine engine, object target, string memberName, bool enumerable = true)
    {
        if (_containsKey != null)
        {
            if (_containsKey.Invoke(target, [_key]) as bool? != true)
            {
                return PropertyDescriptor.Undefined;
            }
        }

        return new ReflectionDescriptor(engine, this, target, memberName, enumerable: true);
    }
}