sebastienros.jint/Jint/Runtime/Interpreter/Expressions/JintMemberExpression.cs

using Jint.Native;
using Jint.Runtime.Environments;

namespace Jint.Runtime.Interpreter.Expressions;

/// <summary>
/// http://www.ecma-international.org/ecma-262/5.1/#sec-11.2.1
/// </summary>
internal sealed class JintMemberExpression : JintExpression
{
    private readonly MemberExpression _memberExpression;
    private JintExpression _objectExpression = null!;
    private JintExpression? _propertyExpression;
    private JsValue? _determinedProperty;
    private bool _initialized;

    private static readonly JsValue _nullMarker = new JsString("NULL MARKER");

    public JintMemberExpression(MemberExpression expression) : base(expression)
    {
        _memberExpression = (MemberExpression) _expression;
    }

    internal static JsValue InitializeDeterminedProperty(MemberExpression expression, bool cache)
    {
        JsValue? property = null;
        if (!expression.Computed)
        {
            if (expression.Property is Identifier identifier)
            {
                property = cache ? JsString.CachedCreate(identifier.Name) : JsString.Create(identifier.Name);
            }
        }
        else if (expression.Property.Type == NodeType.Literal)
        {
            property = JintLiteralExpression.ConvertToJsValue((Literal) expression.Property);
        }

        return property ?? _nullMarker;
    }

    protected override object EvaluateInternal(EvaluationContext context)
    {
        if (!_initialized)
        {
            _objectExpression = Build(_memberExpression.Object);

            _determinedProperty ??= _expression.UserData as JsValue ?? InitializeDeterminedProperty(_memberExpression, cache: false);

            if (ReferenceEquals(_determinedProperty, _nullMarker))
            {
                _propertyExpression = Build(_memberExpression.Property);
                _determinedProperty = null;
            }

            _initialized = true;
        }

        JsValue? actualThis = null;
        object? baseReferenceName = null;
        JsValue? baseValue = null;

        var engine = context.Engine;
        if (_objectExpression is JintIdentifierExpression identifierExpression)
        {
            var identifier = identifierExpression.Identifier;
            baseReferenceName = identifier.Key.Name;
            var env = engine.ExecutionContext.LexicalEnvironment;
            JintEnvironment.TryGetIdentifierEnvironmentWithBindingValue(
                env,
                identifier,
                out _,
                out baseValue);
        }
        else if (_objectExpression is JintThisExpression thisExpression)
        {
            baseValue = (JsValue?) thisExpression.GetValue(context);
        }
        else if (_objectExpression is JintSuperExpression)
        {
            var env = (FunctionEnvironment) engine.ExecutionContext.GetThisEnvironment();
            actualThis = env.GetThisBinding();
            baseValue = env.GetSuperBase();
        }

        if (baseValue is null)
        {
            // fast checks failed
            var baseReference = _objectExpression.Evaluate(context);
            if (ReferenceEquals(JsValue.Undefined, baseReference))
            {
                return JsValue.Undefined;
            }
            if (baseReference is Reference reference)
            {
                baseReferenceName = reference.ReferencedName;
                baseValue = engine.GetValue(reference, returnReferenceToPool: true);
            }
            else
            {
                baseValue = engine.GetValue(baseReference, returnReferenceToPool: false);
            }
        }

        if (baseValue.IsNullOrUndefined() && (_memberExpression.Optional || _objectExpression._expression.IsOptional()))
        {
            return JsValue.Undefined;
        }

        var property = _determinedProperty ?? _propertyExpression!.GetValue(context);
        if (baseValue.IsNullOrUndefined())
        {
            // we can use base data types securely, object evaluation can mess things up
            var referenceName = property.IsPrimitive()
                ? TypeConverter.ToString(property)
                : _determinedProperty?.ToString() ?? baseReferenceName?.ToString();

            TypeConverter.CheckObjectCoercible(engine, baseValue, _memberExpression.Property, referenceName!);
        }

        if (property.IsPrivateName())
        {
            return MakePrivateReference(engine, baseValue, property);
        }

        return context.Engine._referencePool.Rent(baseValue, property, StrictModeScope.IsStrictModeCode, thisValue: actualThis);
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-makeprivatereference
    /// </summary>
    private static Reference MakePrivateReference(Engine engine, JsValue baseValue, JsValue privateIdentifier)
    {
        var privEnv = engine.ExecutionContext.PrivateEnvironment;
        var privateName = privEnv!.ResolvePrivateIdentifier(privateIdentifier.ToString());
        return engine._referencePool.Rent(baseValue, privateName!, strict: true, thisValue: null);
    }
}