Implement `ProxyBuilder` (#2076)

This Pull Request fixes/closes #2075.

It changes the following:

- Implements a `ProxyBuilder` struct to be able to create `Proxy` objects from native function traps.
- Documents `ProxyBuilder` and adjusts some documentation.
- Fixes a clippy lint.

boa_engine/src/builtins/function/mod.rs

@@ -44,6 +44,14 @@ mod tests;
 ///
 /// Native functions need to have this signature in order to
 /// be callable from Javascript.
+///
+/// # Arguments
+///
+/// - The first argument represents the `this` variable of every Javascript function.
+///
+/// - The second argument represents a list of all arguments passed to the function.
+///
+/// - The last argument is the [`Context`] of the engine.
 pub type NativeFunctionSignature = fn(&JsValue, &[JsValue], &mut Context) -> JsResult<JsValue>;
 
 // Allows restricting closures to only `Copy` ones.

boa_engine/src/builtins/proxy/mod.rs

@@ -12,13 +12,12 @@
 
 use crate::{
     builtins::{BuiltIn, JsArgs},
-    object::{ConstructorBuilder, FunctionBuilder, JsObject, ObjectData},
+    object::{ConstructorBuilder, FunctionBuilder, JsFunction, JsObject, ObjectData},
     Context, JsResult, JsValue,
 };
 use boa_gc::{Finalize, Trace};
 use boa_profiler::Profiler;
 use tap::{Conv, Pipe};
-
 /// Javascript `Proxy` object.
 #[derive(Debug, Clone, Trace, Finalize)]
 pub struct Proxy {
@@ -50,7 +49,7 @@ impl BuiltIn for Proxy {
 impl Proxy {
     const LENGTH: usize = 2;
 
-    fn new(target: JsObject, handler: JsObject) -> Self {
+    pub(crate) fn new(target: JsObject, handler: JsObject) -> Self {
         Self {
             data: Some((target, handler)),
         }
@@ -82,7 +81,7 @@ impl Proxy {
         }
 
         // 2. Return ? ProxyCreate(target, handler).
-        Self::create(args.get_or_undefined(0), args.get_or_undefined(1), context)
+        Self::create(args.get_or_undefined(0), args.get_or_undefined(1), context).map(JsValue::from)
     }
 
     // `10.5.14 ProxyCreate ( target, handler )`
@@ -91,7 +90,11 @@ impl Proxy {
     //  - [ECMAScript reference][spec]
     //
     // [spec]: https://tc39.es/ecma262/#sec-proxycreate
-    fn create(target: &JsValue, handler: &JsValue, context: &mut Context) -> JsResult<JsValue> {
+    pub(crate) fn create(
+        target: &JsValue,
+        handler: &JsValue,
+        context: &mut Context,
+    ) -> JsResult<JsObject> {
         // 1. If Type(target) is not Object, throw a TypeError exception.
         let target = target.as_object().ok_or_else(|| {
             context.construct_type_error("Proxy constructor called with non-object target")
@@ -120,52 +123,49 @@ impl Proxy {
         );
 
         // 8. Return P.
-        Ok(p.into())
+        Ok(p)
     }
 
-    /// `28.2.2.1 Proxy.revocable ( target, handler )`
+    pub(crate) fn revoker(proxy: JsObject, context: &mut Context) -> JsFunction {
-    ///
-    /// More information:
-    ///  - [ECMAScript reference][spec]
-    ///
-    /// [spec]: https://tc39.es/ecma262/#sec-proxy.revocable
-    fn revocable(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
-        // 1. Let p be ? ProxyCreate(target, handler).
-        let p = Self::create(args.get_or_undefined(0), args.get_or_undefined(1), context)?;
-
         // 3. Let revoker be ! CreateBuiltinFunction(revokerClosure, 0, "", « [[RevocableProxy]] »).
         // 4. Set revoker.[[RevocableProxy]] to p.
-        let revoker = FunctionBuilder::closure_with_captures(
+        FunctionBuilder::closure_with_captures(
             context,
             |_, _, revocable_proxy, _| {
                 // a. Let F be the active function object.
                 // b. Let p be F.[[RevocableProxy]].
-                // c. If p is null, return undefined.
-                if revocable_proxy.is_null() {
-                    return Ok(JsValue::undefined());
-                }
-
-                let p = revocable_proxy
-                    .as_object()
-                    .expect("[[RevocableProxy]] must be an object or null");
-
-                // e. Assert: p is a Proxy object.
-                // f. Set p.[[ProxyTarget]] to null.
-                // g. Set p.[[ProxyHandler]] to null.
-                p.borrow_mut()
-                    .as_proxy_mut()
-                    .expect("[[RevocableProxy]] must be a proxy object")
-                    .data = None;
-
                 // d. Set F.[[RevocableProxy]] to null.
-                *revocable_proxy = JsValue::Null;
+                if let Some(p) = revocable_proxy.take() {
+                    // e. Assert: p is a Proxy object.
+                    // f. Set p.[[ProxyTarget]] to null.
+                    // g. Set p.[[ProxyHandler]] to null.
+                    p.borrow_mut()
+                        .as_proxy_mut()
+                        .expect("[[RevocableProxy]] must be a proxy object")
+                        .data = None;
+                }
 
+                // c. If p is null, return undefined.
                 // h. Return undefined.
                 Ok(JsValue::undefined())
             },
-            p.clone(),
+            Some(proxy),
         )
-        .build();
+        .build()
+    }
+
+    /// `28.2.2.1 Proxy.revocable ( target, handler )`
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-proxy.revocable
+    fn revocable(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
+        // 1. Let p be ? ProxyCreate(target, handler).
+        let p = Self::create(args.get_or_undefined(0), args.get_or_undefined(1), context)?;
+
+        // Revoker creation steps on `Proxy::revoker`
+        let revoker = Self::revoker(p.clone(), context);
 
         // 5. Let result be ! OrdinaryObjectCreate(%Object.prototype%).
         let result = context.construct_object();

boa_engine/src/object/internal_methods/bound_function.rs

@@ -11,7 +11,6 @@ use super::{InternalObjectMethods, ORDINARY_INTERNAL_METHODS};
 pub(crate) static BOUND_FUNCTION_EXOTIC_INTERNAL_METHODS: InternalObjectMethods =
     InternalObjectMethods {
         __call__: Some(bound_function_exotic_call),
-        __construct__: None,
         ..ORDINARY_INTERNAL_METHODS
     };
 

boa_engine/src/object/internal_methods/proxy.rs

@@ -32,36 +32,15 @@ pub(crate) static PROXY_EXOTIC_INTERNAL_METHODS_BASIC: InternalObjectMethods =
 
 pub(crate) static PROXY_EXOTIC_INTERNAL_METHODS_WITH_CALL: InternalObjectMethods =
     InternalObjectMethods {
-        __get_prototype_of__: proxy_exotic_get_prototype_of,
-        __set_prototype_of__: proxy_exotic_set_prototype_of,
-        __is_extensible__: proxy_exotic_is_extensible,
-        __prevent_extensions__: proxy_exotic_prevent_extensions,
-        __get_own_property__: proxy_exotic_get_own_property,
-        __define_own_property__: proxy_exotic_define_own_property,
-        __has_property__: proxy_exotic_has_property,
-        __get__: proxy_exotic_get,
-        __set__: proxy_exotic_set,
-        __delete__: proxy_exotic_delete,
-        __own_property_keys__: proxy_exotic_own_property_keys,
         __call__: Some(proxy_exotic_call),
-        __construct__: None,
+        ..PROXY_EXOTIC_INTERNAL_METHODS_BASIC
     };
 
 pub(crate) static PROXY_EXOTIC_INTERNAL_METHODS_ALL: InternalObjectMethods =
     InternalObjectMethods {
-        __get_prototype_of__: proxy_exotic_get_prototype_of,
-        __set_prototype_of__: proxy_exotic_set_prototype_of,
-        __is_extensible__: proxy_exotic_is_extensible,
-        __prevent_extensions__: proxy_exotic_prevent_extensions,
-        __get_own_property__: proxy_exotic_get_own_property,
-        __define_own_property__: proxy_exotic_define_own_property,
-        __has_property__: proxy_exotic_has_property,
-        __get__: proxy_exotic_get,
-        __set__: proxy_exotic_set,
-        __delete__: proxy_exotic_delete,
-        __own_property_keys__: proxy_exotic_own_property_keys,
         __call__: Some(proxy_exotic_call),
         __construct__: Some(proxy_exotic_construct),
+        ..PROXY_EXOTIC_INTERNAL_METHODS_BASIC
     };
 
 /// `10.5.1 [[GetPrototypeOf]] ( )`

boa_engine/src/object/jsproxy.rs

@@ -0,0 +1,477 @@
+use boa_gc::{Finalize, Trace};
+
+use crate::{
+    builtins::{function::NativeFunctionSignature, Proxy},
+    Context, JsResult, JsValue,
+};
+
+use super::{FunctionBuilder, JsFunction, JsObject, JsObjectType, ObjectData};
+
+/// JavaScript [`Proxy`][proxy] rust object.
+///
+/// This is a wrapper type for the [`Proxy`][proxy] API that allows customizing
+/// essential behaviour for an object, like [property accesses][get] or the
+/// [`delete`][delete] operator.
+///
+/// The only way to construct this type is to use the [`JsProxyBuilder`] type; also
+/// accessible from [`JsProxy::builder`].
+///
+/// [get]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/get
+/// [delete]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/deleteProperty
+/// [proxy]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
+#[derive(Debug, Clone, Trace, Finalize)]
+pub struct JsProxy {
+    inner: JsObject,
+}
+
+impl JsProxy {
+    pub fn builder(target: JsObject) -> JsProxyBuilder {
+        JsProxyBuilder::new(target)
+    }
+}
+
+impl From<JsProxy> for JsObject {
+    #[inline]
+    fn from(o: JsProxy) -> Self {
+        o.inner.clone()
+    }
+}
+
+impl From<JsProxy> for JsValue {
+    #[inline]
+    fn from(o: JsProxy) -> Self {
+        o.inner.clone().into()
+    }
+}
+
+impl std::ops::Deref for JsProxy {
+    type Target = JsObject;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl JsObjectType for JsProxy {}
+
+/// JavaScript [`Proxy`][proxy] rust object that can be disabled.
+///
+/// Safe interface for the [`Proxy.revocable`][revocable] method that creates a
+/// proxy that can be disabled using the [`JsRevocableProxy::revoke`] method.
+/// The internal proxy is accessible using the [`Deref`][`std::ops::Deref`] operator.
+///
+/// The only way to construct this type is to use the [`JsProxyBuilder`] type; also
+/// accessible from [`JsProxy::builder`]; with the [`JsProxyBuilder::build_revocable`]
+/// method.
+///
+/// [revocable]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/revocable
+#[derive(Debug, Trace, Finalize)]
+pub struct JsRevocableProxy {
+    proxy: JsProxy,
+    revoker: JsFunction,
+}
+
+impl JsRevocableProxy {
+    /// Disables the traps of the internal `proxy` object, essentially
+    /// making it unusable and throwing `TypeError`s for all the traps.
+    pub fn revoke(self, context: &mut Context) -> JsResult<()> {
+        self.revoker.call(&JsValue::undefined(), &[], context)?;
+        Ok(())
+    }
+}
+
+impl std::ops::Deref for JsRevocableProxy {
+    type Target = JsProxy;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.proxy
+    }
+}
+
+/// Utility builder to create [`JsProxy`] objects from native functions.
+///
+/// This builder can be used when you need to create [`Proxy`] objects
+/// from Rust instead of Javascript, which should generate faster
+/// trap functions than its Javascript counterparts.
+#[must_use]
+#[derive(Clone)]
+pub struct JsProxyBuilder {
+    target: JsObject,
+    apply: Option<NativeFunctionSignature>,
+    construct: Option<NativeFunctionSignature>,
+    define_property: Option<NativeFunctionSignature>,
+    delete_property: Option<NativeFunctionSignature>,
+    get: Option<NativeFunctionSignature>,
+    get_own_property_descriptor: Option<NativeFunctionSignature>,
+    get_prototype_of: Option<NativeFunctionSignature>,
+    has: Option<NativeFunctionSignature>,
+    is_extensible: Option<NativeFunctionSignature>,
+    own_keys: Option<NativeFunctionSignature>,
+    prevent_extensions: Option<NativeFunctionSignature>,
+    set: Option<NativeFunctionSignature>,
+    set_prototype_of: Option<NativeFunctionSignature>,
+}
+
+impl std::fmt::Debug for JsProxyBuilder {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        #[derive(Debug)]
+        struct NativeFunction;
+        f.debug_struct("ProxyBuilder")
+            .field("target", &self.target)
+            .field("apply", &self.apply.map(|_| NativeFunction))
+            .field("construct", &self.construct.map(|_| NativeFunction))
+            .field(
+                "define_property",
+                &self.define_property.map(|_| NativeFunction),
+            )
+            .field(
+                "delete_property",
+                &self.delete_property.map(|_| NativeFunction),
+            )
+            .field("get", &self.get.map(|_| NativeFunction))
+            .field(
+                "get_own_property_descriptor",
+                &self.get_own_property_descriptor.map(|_| NativeFunction),
+            )
+            .field(
+                "get_prototype_of",
+                &self.get_prototype_of.map(|_| NativeFunction),
+            )
+            .field("has", &self.has.map(|_| NativeFunction))
+            .field("is_extensible", &self.is_extensible.map(|_| NativeFunction))
+            .field("own_keys", &self.own_keys.map(|_| NativeFunction))
+            .field(
+                "prevent_extensions",
+                &self.prevent_extensions.map(|_| NativeFunction),
+            )
+            .field("set", &self.set.map(|_| NativeFunction))
+            .field(
+                "set_prototype_of",
+                &self.set_prototype_of.map(|_| NativeFunction),
+            )
+            .finish()
+    }
+}
+
+impl JsProxyBuilder {
+    /// Create a new `ProxyBuilder` with every trap set to `undefined`.
+    pub fn new(target: JsObject) -> Self {
+        Self {
+            target,
+            apply: None,
+            construct: None,
+            define_property: None,
+            delete_property: None,
+            get: None,
+            get_own_property_descriptor: None,
+            get_prototype_of: None,
+            has: None,
+            is_extensible: None,
+            own_keys: None,
+            prevent_extensions: None,
+            set: None,
+            set_prototype_of: None,
+        }
+    }
+
+    /// Set the `apply` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// # Note
+    ///
+    /// If the `target` object is not a function, then `apply` will be ignored
+    /// when trying to call the proxy, which will throw a type error.
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/apply
+    pub fn apply(mut self, apply: NativeFunctionSignature) -> Self {
+        self.apply = Some(apply);
+        self
+    }
+
+    /// Set the `construct` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// # Note
+    ///
+    /// If the `target` object is not a constructor, then `construct` will be ignored
+    /// when trying to construct an object using the proxy, which will throw a type error.
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/construct
+    pub fn construct(mut self, construct: NativeFunctionSignature) -> Self {
+        self.construct = Some(construct);
+        self
+    }
+
+    /// Set the `defineProperty` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/defineProperty
+    pub fn define_property(mut self, define_property: NativeFunctionSignature) -> Self {
+        self.define_property = Some(define_property);
+        self
+    }
+
+    /// Set the `deleteProperty` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/deleteProperty
+    pub fn delete_property(mut self, delete_property: NativeFunctionSignature) -> Self {
+        self.delete_property = Some(delete_property);
+        self
+    }
+
+    /// Set the `get` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/get
+    pub fn get(mut self, get: NativeFunctionSignature) -> Self {
+        self.get = Some(get);
+        self
+    }
+
+    /// Set the `getOwnPropertyDescriptor` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/getOwnPropertyDescriptor
+    pub fn get_own_property_descriptor(
+        mut self,
+        get_own_property_descriptor: NativeFunctionSignature,
+    ) -> Self {
+        self.get_own_property_descriptor = Some(get_own_property_descriptor);
+        self
+    }
+
+    /// Set the `getPrototypeOf` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/getPrototypeOf
+    pub fn get_prototype_of(mut self, get_prototype_of: NativeFunctionSignature) -> Self {
+        self.get_prototype_of = Some(get_prototype_of);
+        self
+    }
+
+    /// Set the `has` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/has
+    pub fn has(mut self, has: NativeFunctionSignature) -> Self {
+        self.has = Some(has);
+        self
+    }
+
+    /// Set the `isExtensible` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/isExtensible
+    pub fn is_extensible(mut self, is_extensible: NativeFunctionSignature) -> Self {
+        self.is_extensible = Some(is_extensible);
+        self
+    }
+
+    /// Set the `ownKeys` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/ownKeys
+    pub fn own_keys(mut self, own_keys: NativeFunctionSignature) -> Self {
+        self.own_keys = Some(own_keys);
+        self
+    }
+
+    /// Set the `preventExtensions` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/preventExtensions
+    pub fn prevent_extensions(mut self, prevent_extensions: NativeFunctionSignature) -> Self {
+        self.prevent_extensions = Some(prevent_extensions);
+        self
+    }
+
+    /// Set the `set` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/set
+    pub fn set(mut self, set: NativeFunctionSignature) -> Self {
+        self.set = Some(set);
+        self
+    }
+
+    /// Set the `setPrototypeOf` proxy trap to the specified native function.
+    ///
+    /// More information:
+    ///
+    /// - [MDN documentation][mdn]
+    ///
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/setPrototypeOf
+    pub fn set_prototype_of(mut self, set_prototype_of: NativeFunctionSignature) -> Self {
+        self.set_prototype_of = Some(set_prototype_of);
+        self
+    }
+
+    /// Build a [`JsObject`] of kind [`Proxy`].
+    ///
+    /// Equivalent to the `Proxy ( target, handler )` constructor, but returns a
+    /// [`JsObject`] in case there's a need to manipulate the returned object
+    /// inside Rust code.
+    #[must_use]
+    pub fn build(self, context: &mut Context) -> JsProxy {
+        let handler = context.construct_object();
+
+        if let Some(apply) = self.apply {
+            let f = FunctionBuilder::native(context, apply).length(3).build();
+            handler
+                .create_data_property_or_throw("apply", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(construct) = self.construct {
+            let f = FunctionBuilder::native(context, construct)
+                .length(3)
+                .build();
+            handler
+                .create_data_property_or_throw("construct", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(define_property) = self.define_property {
+            let f = FunctionBuilder::native(context, define_property)
+                .length(3)
+                .build();
+            handler
+                .create_data_property_or_throw("defineProperty", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(delete_property) = self.delete_property {
+            let f = FunctionBuilder::native(context, delete_property)
+                .length(2)
+                .build();
+            handler
+                .create_data_property_or_throw("deleteProperty", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(get) = self.get {
+            let f = FunctionBuilder::native(context, get).length(3).build();
+            handler
+                .create_data_property_or_throw("get", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(get_own_property_descriptor) = self.get_own_property_descriptor {
+            let f = FunctionBuilder::native(context, get_own_property_descriptor)
+                .length(2)
+                .build();
+            handler
+                .create_data_property_or_throw("getOwnPropertyDescriptor", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(get_prototype_of) = self.get_prototype_of {
+            let f = FunctionBuilder::native(context, get_prototype_of)
+                .length(1)
+                .build();
+            handler
+                .create_data_property_or_throw("getPrototypeOf", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(has) = self.has {
+            let f = FunctionBuilder::native(context, has).length(2).build();
+            handler
+                .create_data_property_or_throw("has", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(is_extensible) = self.is_extensible {
+            let f = FunctionBuilder::native(context, is_extensible)
+                .length(1)
+                .build();
+            handler
+                .create_data_property_or_throw("isExtensible", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(own_keys) = self.own_keys {
+            let f = FunctionBuilder::native(context, own_keys).length(1).build();
+            handler
+                .create_data_property_or_throw("ownKeys", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(prevent_extensions) = self.prevent_extensions {
+            let f = FunctionBuilder::native(context, prevent_extensions)
+                .length(1)
+                .build();
+            handler
+                .create_data_property_or_throw("preventExtensions", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(set) = self.set {
+            let f = FunctionBuilder::native(context, set).length(4).build();
+            handler
+                .create_data_property_or_throw("set", f, context)
+                .expect("new object should be writable");
+        }
+        if let Some(set_prototype_of) = self.set_prototype_of {
+            let f = FunctionBuilder::native(context, set_prototype_of)
+                .length(2)
+                .build();
+            handler
+                .create_data_property_or_throw("setPrototypeOf", f, context)
+                .expect("new object should be writable");
+        }
+
+        let callable = self.target.is_callable();
+        let constructor = self.target.is_constructor();
+
+        let proxy = JsObject::from_proto_and_data(
+            context.intrinsics().constructors().object().prototype(),
+            ObjectData::proxy(Proxy::new(self.target, handler), callable, constructor),
+        );
+
+        JsProxy { inner: proxy }
+    }
+
+    /// Builds a [`JsObject`] of kind [`Proxy`] and a [`JsFunction`] that, when
+    /// called, disables the proxy of the object.
+    ///
+    /// Equivalent to the `Proxy.revocable ( target, handler )` static method,
+    /// but returns a [`JsObject`] for the proxy and a [`JsFunction`] for the
+    /// revoker in case there's a need to manipulate the returned objects
+    /// inside Rust code.
+    #[must_use]
+    pub fn build_revocable(self, context: &mut Context) -> JsRevocableProxy {
+        let proxy = self.build(context);
+        let revoker = Proxy::revoker(proxy.inner.clone(), context);
+
+        JsRevocableProxy { proxy, revoker }
+    }
+}

boa_engine/src/object/mod.rs

@@ -61,12 +61,14 @@ pub(crate) mod internal_methods;
 mod jsarray;
 mod jsfunction;
 mod jsobject;
+mod jsproxy;
 mod jstypedarray;
 mod operations;
 mod property_map;
 
 pub use jsarray::*;
 pub use jsfunction::*;
+pub use jsproxy::*;
 pub use jstypedarray::*;
 
 pub(crate) trait JsObjectType:

boa_engine/src/string.rs

@@ -626,7 +626,7 @@ impl Inner {
 /// The `JsString` length and data is stored on the heap. and just an non-null
 /// pointer is kept, so its size is the size of a pointer.
 ///
-/// We define some commonly used string constants in [`CONSTANTS_ARRAY`]. For these
+/// We define some commonly used string constants in an interner. For these
 /// strings, we no longer allocate memory on the heap to reduce the overhead of
 /// memory allocation and reference counting.
 #[derive(Finalize)]