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

using Jint.Collections;
using Jint.Native;
using Jint.Native.Function;
using Jint.Native.Object;
using Jint.Runtime.Descriptors;

namespace Jint.Runtime.Interpreter.Expressions;

/// <summary>
/// https://tc39.es/ecma262/#sec-object-initializer
/// </summary>
internal sealed class JintObjectExpression : JintExpression
{
    private readonly ExpressionCache _valueExpressions = new();
    private ObjectProperty?[] _properties = [];

    // check if we can do a shortcut when all are object properties
    // and don't require duplicate checking
    private bool _canBuildFast;
    private bool _initialized;

    private sealed class ObjectProperty
    {
        internal readonly string? _key;
        private JsString? _keyJsString;
        internal readonly Property _value;
        private JintFunctionDefinition? _functionDefinition;

        public ObjectProperty(string? key, Property property)
        {
            _key = key;
            _value = property;
        }

        public JsString? KeyJsString => _keyJsString ??= _key != null ? JsString.Create(_key) : null;

        public JintFunctionDefinition GetFunctionDefinition(Engine engine)
        {
            if (_functionDefinition is not null)
            {
                return _functionDefinition;
            }

            var function = _value.Value as IFunction;
            if (function is null)
            {
                ExceptionHelper.ThrowSyntaxError(engine.Realm);
            }

            _functionDefinition = new JintFunctionDefinition(function);
            return _functionDefinition;
        }
    }

    private JintObjectExpression(ObjectExpression expression) : base(expression)
    {
    }

    public static JintExpression Build(ObjectExpression expression)
    {
        return expression.Properties.Count == 0
            ? JintEmptyObjectExpression.Instance
            : new JintObjectExpression(expression);
    }

    private void Initialize(EvaluationContext context)
    {
        _canBuildFast = true;
        var expression = (ObjectExpression) _expression;
        ref readonly var properties = ref expression.Properties;

        var valueExpressions = new Expression[properties.Count];
        _properties = new ObjectProperty[properties.Count];

        for (var i = 0; i < _properties.Length; i++)
        {
            string? propName = null;
            var property = properties[i];
            if (property is Acornima.Ast.ObjectProperty p)
            {
                if (p.Key is Literal literal)
                {
                    propName = AstExtensions.LiteralKeyToString(literal);
                }

                if (!p.Computed && p.Key is Identifier identifier)
                {
                    propName = identifier.Name;
                    _canBuildFast &= !string.Equals(propName, "__proto__", StringComparison.Ordinal);
                }

                _properties[i] = new ObjectProperty(propName, p);

                if (p.Kind is PropertyKind.Init)
                {
                    var propertyValue = p.Value;
                    valueExpressions[i] = (Expression) propertyValue;
                    _canBuildFast &= !propertyValue.IsFunctionDefinition();
                }
                else
                {
                    _canBuildFast = false;
                }
            }
            else if (property is SpreadElement spreadElement)
            {
                _canBuildFast = false;
                _properties[i] = null;
                valueExpressions[i] = spreadElement.Argument;
            }
            else
            {
                ExceptionHelper.ThrowArgumentOutOfRangeException("property", "cannot handle property " + property);
            }

            _canBuildFast &= propName != null;
        }

        _valueExpressions.Initialize(context, valueExpressions.AsSpan());
    }

    protected override object EvaluateInternal(EvaluationContext context)
    {
        if (!_initialized)
        {
            Initialize(context);
            _initialized = true;
        }

        return _canBuildFast
            ? BuildObjectFast(context)
            : BuildObjectNormal(context);
    }

    /// <summary>
    /// Version that can safely build plain object with only normal init/data fields fast.
    /// </summary>
    private JsObject BuildObjectFast(EvaluationContext context)
    {
        var obj = new JsObject(context.Engine);
        var properties = new PropertyDictionary(_properties.Length, checkExistingKeys: true);
        for (var i = 0; i < _properties.Length; i++)
        {
            var objectProperty = _properties[i];
            var propValue = _valueExpressions.GetValue(context, i);
            properties[objectProperty!._key!] = new PropertyDescriptor(propValue, PropertyFlag.ConfigurableEnumerableWritable);
        }

        obj.SetProperties(properties);
        return obj;
    }

    /// <summary>
    /// https://tc39.es/ecma262/#sec-object-initializer-runtime-semantics-propertydefinitionevaluation
    /// </summary>
    private object BuildObjectNormal(EvaluationContext context)
    {
        var engine = context.Engine;
        var obj = engine.Realm.Intrinsics.Object.Construct(_properties.Length);

        for (var i = 0; i < _properties.Length; i++)
        {
            var objectProperty = _properties[i];

            if (objectProperty is null)
            {
                // spread
                if (_valueExpressions.GetValue(context, i) is ObjectInstance source)
                {
                    source.CopyDataProperties(obj, excludedItems: null);
                }

                continue;
            }

            var property = objectProperty._value;

            if (property.Method)
            {
                ClassDefinition.MethodDefinitionEvaluation(engine, obj, property, enumerable: true);
                continue;
            }

            JsValue? propName = objectProperty.KeyJsString;
            if (propName is null)
            {
                var value = property.TryGetKey(engine);
                if (context.IsAbrupt())
                {
                    return value;
                }

                propName = TypeConverter.ToPropertyKey(value);
            }

            if (property.Kind == PropertyKind.Init)
            {
                var propValue = _valueExpressions.GetValue(context, i)!;
                if (string.Equals(objectProperty._key, "__proto__", StringComparison.Ordinal) && !objectProperty._value.Computed && !objectProperty._value.Shorthand)
                {
                    if (propValue.IsObject() || propValue.IsNull())
                    {
                        obj.SetPrototypeOf(propValue);
                    }
                    continue;
                }

                if (_valueExpressions.IsAnonymousFunctionDefinition(i))
                {
                    var closure = (Function) propValue;
                    closure.SetFunctionName(propName);
                }

                obj.CreateDataPropertyOrThrow(propName, propValue);
            }
            else if (property.Kind is PropertyKind.Get or PropertyKind.Set)
            {
                var function = objectProperty.GetFunctionDefinition(engine);
                var closure = engine.Realm.Intrinsics.Function.OrdinaryFunctionCreate(
                    engine.Realm.Intrinsics.Function.PrototypeObject,
                    function,
                    function.ThisMode,
                    engine.ExecutionContext.LexicalEnvironment,
                    engine.ExecutionContext.PrivateEnvironment);

                closure.SetFunctionName(propName, property.Kind == PropertyKind.Get ? "get" : "set");
                closure.MakeMethod(obj);

                var propDesc = new GetSetPropertyDescriptor(
                    get: property.Kind == PropertyKind.Get ? closure : null,
                    set: property.Kind == PropertyKind.Set ? closure : null,
                    PropertyFlag.Enumerable | PropertyFlag.Configurable);

                obj.DefinePropertyOrThrow(propName, propDesc);
            }
        }

        return obj;
    }

    internal sealed class JintEmptyObjectExpression : JintExpression
    {
        public static JintEmptyObjectExpression Instance = new(new ObjectExpression(NodeList.From(Array.Empty<Node>())));

        private JintEmptyObjectExpression(Expression expression) : base(expression)
        {
        }

        protected override object EvaluateInternal(EvaluationContext context)
        {
            return new JsObject(context.Engine);
        }

        public override JsValue GetValue(EvaluationContext context)
        {
            return new JsObject(context.Engine);
        }
    }
}