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 )`
-    ///
-    /// 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)?;
-
+    pub(crate) fn revoker(proxy: JsObject, context: &mut Context) -> JsFunction {
         // 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]] ( )`