feat(script): implement some of the non-ordinary internal methods of Location

<https://html.spec.whatwg.org/multipage/#the-location-interface>

 - `[[GetPrototypeOf]]`: not yet
 - `[[SetPrototypeOf]]`: not yet
 - `[[IsExtensible]]`: `proxyhandler::is_extensible`
 - `[[PreventExtensions]]`: `proxyhandler::prevent_extensions`
 - `[[GetOwnProperty]]`: `CGDOMJSProxyHandler_getOwnPropertyDescriptor` (updated)
 - `[[DefineOwnProperty]]`: `CGDOMJSProxyHandler_defineProperty` (updated)
 - `[[Get]]`: `CGDOMJSProxyHandler_get` (updated)
 - `[[Set]]`: not yet
 - `[[Delete]]`: `CGDOMJSProxyHandler_delete` (updated)
 - `[[OwnPropertyKeys]]`: `CGDOMJSProxyHandler_ownPropertyKeys` (updated)

components/script/dom/bindings/proxyhandler.rs

@@ -7,24 +7,43 @@
 #![deny(missing_docs)]
 
 use crate::dom::bindings::conversions::is_dom_proxy;
+use crate::dom::bindings::error::{throw_dom_exception, Error};
+use crate::dom::bindings::principals::ServoJSPrincipalsRef;
 use crate::dom::bindings::utils::delete_property_by_id;
-use js::glue::GetProxyHandlerFamily;
+use crate::dom::globalscope::GlobalScope;
+use crate::realms::{AlreadyInRealm, InRealm};
+use crate::script_runtime::JSContext as SafeJSContext;
+use js::conversions::ToJSValConvertible;
+use js::glue::{
+    GetProxyHandler, GetProxyHandlerFamily, InvokeGetOwnPropertyDescriptor, RUST_SYMBOL_TO_JSID,
+};
 use js::glue::{GetProxyPrivate, SetProxyPrivate};
+use js::jsapi;
 use js::jsapi::GetStaticPrototype;
 use js::jsapi::Handle as RawHandle;
 use js::jsapi::HandleId as RawHandleId;
 use js::jsapi::HandleObject as RawHandleObject;
+use js::jsapi::HandleValue as RawHandleValue;
+use js::jsapi::JS_AtomizeAndPinString;
 use js::jsapi::JS_DefinePropertyById;
+use js::jsapi::JS_GetOwnPropertyDescriptorById;
+use js::jsapi::JS_IsExceptionPending;
+use js::jsapi::MutableHandle as RawMutableHandle;
+use js::jsapi::MutableHandleIdVector as RawMutableHandleIdVector;
 use js::jsapi::MutableHandleObject as RawMutableHandleObject;
+use js::jsapi::MutableHandleValue as RawMutableHandleValue;
 use js::jsapi::ObjectOpResult;
+use js::jsapi::{jsid, GetObjectRealmOrNull, GetRealmPrincipals, JSFunctionSpec, JSPropertySpec};
 use js::jsapi::{DOMProxyShadowsResult, JSContext, JSObject, PropertyDescriptor};
+use js::jsapi::{GetWellKnownSymbol, SymbolCode};
 use js::jsapi::{JSErrNum, SetDOMProxyInformation};
 use js::jsval::ObjectValue;
 use js::jsval::UndefinedValue;
 use js::rust::wrappers::JS_AlreadyHasOwnPropertyById;
 use js::rust::wrappers::JS_NewObjectWithGivenProto;
-use js::rust::{Handle, HandleObject, MutableHandle, MutableHandleObject};
-use std::ptr;
+use js::rust::wrappers::{AppendToIdVector, RUST_INTERNED_STRING_TO_JSID};
+use js::rust::{get_context_realm, Handle, HandleObject, MutableHandle, MutableHandleObject};
+use std::{ffi::CStr, ptr};
 
 /// Determine if this id shadows any existing properties for this proxy.
 pub unsafe extern "C" fn shadow_check_callback(
@@ -177,3 +196,322 @@ pub fn fill_property_descriptor(
     desc.getter = None;
     desc.setter = None;
 }
+
+/// <https://html.spec.whatwg.org/multipage/#isplatformobjectsameorigin-(-o-)>
+pub unsafe fn is_platform_object_same_origin(cx: SafeJSContext, obj: RawHandleObject) -> bool {
+    let subject_realm = get_context_realm(*cx);
+    let obj_realm = GetObjectRealmOrNull(*obj);
+    assert!(!obj_realm.is_null());
+
+    let subject = ServoJSPrincipalsRef::from_raw_unchecked(GetRealmPrincipals(subject_realm));
+    let obj = ServoJSPrincipalsRef::from_raw_unchecked(GetRealmPrincipals(obj_realm));
+
+    let subject_origin = subject.origin();
+    let obj_origin = obj.origin();
+
+    subject_origin.same_origin_domain(&obj_origin)
+}
+
+/// Report a cross-origin denial for a property, Always returns `false`, so it
+/// can be used as `return report_cross_origin_denial(...);`.
+///
+/// What this function does corresponds to the operations in
+/// <https://html.spec.whatwg.org/multipage/#the-location-interface> denoted as
+/// "Throw a `SecurityError` DOMException".
+pub unsafe fn report_cross_origin_denial(
+    cx: SafeJSContext,
+    _id: RawHandleId,
+    _access: &str,
+) -> bool {
+    let in_realm_proof = AlreadyInRealm::assert_for_cx(cx);
+    if !JS_IsExceptionPending(*cx) {
+        let global = GlobalScope::from_context(*cx, InRealm::Already(&in_realm_proof));
+        // TODO: include `id` and `access` in the exception message
+        throw_dom_exception(cx, &*global, Error::Security);
+    }
+    false
+}
+
+/// Property and method specs that correspond to the elements of
+/// [`CrossOriginProperties(O)`].
+///
+/// [`CrossOriginProperties(O)`]: https://html.spec.whatwg.org/multipage/#crossoriginproperties-(-o-)
+pub struct CrossOriginProperties {
+    pub attributes: &'static [JSPropertySpec],
+    pub methods: &'static [JSFunctionSpec],
+}
+
+impl CrossOriginProperties {
+    /// Enumerate the property keys defined by `self`.
+    fn keys(&self) -> impl Iterator<Item = *const std::os::raw::c_char> + '_ {
+        // Safety: All cross-origin property keys are strings, not symbols
+        self.attributes
+            .iter()
+            .map(|spec| unsafe { spec.name.string_ })
+            .chain(self.methods.iter().map(|spec| unsafe { spec.name.string_ }))
+            .filter(|ptr| !ptr.is_null())
+    }
+}
+
+/// Implementation of [`CrossOriginOwnPropertyKeys`].
+///
+/// [`CrossOriginOwnPropertyKeys`]: https://html.spec.whatwg.org/multipage/#crossoriginownpropertykeys-(-o-)
+pub unsafe fn cross_origin_own_property_keys(
+    cx: SafeJSContext,
+    _proxy: RawHandleObject,
+    cross_origin_properties: &'static CrossOriginProperties,
+    props: RawMutableHandleIdVector,
+) -> bool {
+    for key in cross_origin_properties.keys() {
+        let jsstring = JS_AtomizeAndPinString(*cx, key);
+        rooted!(in(*cx) let rooted = jsstring);
+        rooted!(in(*cx) let mut rooted_jsid: jsid);
+        RUST_INTERNED_STRING_TO_JSID(*cx, rooted.handle().get(), rooted_jsid.handle_mut());
+        AppendToIdVector(props, rooted_jsid.handle());
+    }
+    true
+}
+
+/// Implementation of [`CrossOriginGet`].
+///
+/// [`CrossOriginGet`]: https://html.spec.whatwg.org/multipage/#crossoriginget-(-o,-p,-receiver-)
+pub unsafe fn cross_origin_get(
+    cx: SafeJSContext,
+    proxy: RawHandleObject,
+    receiver: RawHandleValue,
+    id: RawHandleId,
+    vp: RawMutableHandleValue,
+) -> bool {
+    // > 1. Let `desc` be `? O.[[GetOwnProperty]](P)`.
+    rooted!(in(*cx) let mut descriptor = PropertyDescriptor::default());
+    if !InvokeGetOwnPropertyDescriptor(
+        GetProxyHandler(*proxy),
+        *cx,
+        proxy,
+        id,
+        descriptor.handle_mut().into(),
+    ) {
+        return false;
+    }
+    //    let descriptor = descriptor.get();
+
+    // > 2. Assert: `desc` is not undefined.
+    assert!(
+        !descriptor.obj.is_null(),
+        "Callees should throw in all cases when they are not finding \
+        a property decriptor"
+    );
+
+    // > 3. If `! IsDataDescriptor(desc)` is true, then return `desc.[[Value]]`.
+    if is_data_descriptor(&descriptor) {
+        vp.set(descriptor.value);
+        return true;
+    }
+
+    // > 4. Assert: `IsAccessorDescriptor(desc)` is `true`.
+    assert!(is_accessor_descriptor(&descriptor));
+
+    // > 5. Let `getter` be `desc.[[Get]]`.
+    // >
+    // > 6. If `getter` is `undefined`, then throw a `SecurityError`
+    // >    `DOMException`.
+    rooted!(in(*cx) let mut getter = ptr::null_mut::<JSObject>());
+    get_getter_object(&descriptor, getter.handle_mut().into());
+    if getter.get().is_null() {
+        return report_cross_origin_denial(cx, id, "get");
+    }
+
+    rooted!(in(*cx) let mut getter_jsval = UndefinedValue());
+    getter.get().to_jsval(*cx, getter_jsval.handle_mut());
+
+    // > 7. Return `? Call(getter, Receiver)`.
+    jsapi::Call(
+        *cx,
+        receiver,
+        getter_jsval.handle().into(),
+        &jsapi::HandleValueArray::new(),
+        vp,
+    )
+}
+
+unsafe fn get_getter_object(d: &PropertyDescriptor, out: RawMutableHandleObject) {
+    if (d.attrs & jsapi::JSPROP_GETTER as u32) != 0 {
+        out.set(std::mem::transmute(d.getter));
+    }
+}
+
+/// <https://tc39.es/ecma262/#sec-isaccessordescriptor>
+fn is_accessor_descriptor(d: &PropertyDescriptor) -> bool {
+    d.attrs & (jsapi::JSPROP_GETTER as u32 | jsapi::JSPROP_SETTER as u32) != 0
+}
+
+/// <https://tc39.es/ecma262/#sec-isdatadescriptor>
+fn is_data_descriptor(d: &PropertyDescriptor) -> bool {
+    let is_accessor = is_accessor_descriptor(d);
+    let is_generic = d.attrs &
+        (jsapi::JSPROP_GETTER as u32 |
+            jsapi::JSPROP_SETTER as u32 |
+            jsapi::JSPROP_IGNORE_READONLY |
+            jsapi::JSPROP_IGNORE_VALUE) ==
+        jsapi::JSPROP_IGNORE_READONLY | jsapi::JSPROP_IGNORE_VALUE;
+    !is_accessor && !is_generic
+}
+
+/// Evaluate `CrossOriginGetOwnPropertyHelper(proxy, id) != null`.
+pub unsafe fn cross_origin_has_own(
+    cx: SafeJSContext,
+    _proxy: RawHandleObject,
+    cross_origin_properties: &'static CrossOriginProperties,
+    id: RawHandleId,
+    bp: *mut bool,
+) -> bool {
+    // TODO: Once we have the slot for the holder, it'd be more efficient to
+    //       use `ensure_cross_origin_property_holder`.
+    *bp = if let Some(key) =
+        crate::dom::bindings::conversions::jsid_to_string(*cx, Handle::from_raw(id))
+    {
+        cross_origin_properties.keys().any(|defined_key| {
+            let defined_key = CStr::from_ptr(defined_key);
+            defined_key.to_bytes() == key.as_bytes()
+        })
+    } else {
+        false
+    };
+
+    true
+}
+
+/// Implementation of [`CrossOriginGetOwnPropertyHelper`].
+///
+/// `cx` and `obj` are expected to be different-Realm here. `obj` can be a
+/// `WindowProxy` or a `Location` or a `DissimilarOrigin*` proxy for one of
+/// those.
+///
+/// [`CrossOriginGetOwnPropertyHelper`]: https://html.spec.whatwg.org/multipage/#crossorigingetownpropertyhelper-(-o,-p-)
+pub unsafe fn cross_origin_get_own_property_helper(
+    cx: SafeJSContext,
+    proxy: RawHandleObject,
+    cross_origin_properties: &'static CrossOriginProperties,
+    id: RawHandleId,
+    mut desc: RawMutableHandle<PropertyDescriptor>,
+) -> bool {
+    rooted!(in(*cx) let mut holder = ptr::null_mut::<JSObject>());
+
+    ensure_cross_origin_property_holder(
+        cx,
+        proxy,
+        cross_origin_properties,
+        holder.handle_mut().into(),
+    );
+
+    if !JS_GetOwnPropertyDescriptorById(*cx, holder.handle().into(), id, desc) {
+        return false;
+    }
+
+    if !desc.obj.is_null() {
+        desc.obj = proxy.get();
+    }
+
+    true
+}
+
+/// Implementation of [`CrossOriginPropertyFallback`].
+///
+
+/// [`CrossOriginPropertyFallback`]: https://html.spec.whatwg.org/multipage/#crossoriginpropertyfallback-(-p-)
+pub unsafe fn cross_origin_property_fallback(
+    cx: SafeJSContext,
+    proxy: RawHandleObject,
+    id: RawHandleId,
+    mut desc: RawMutableHandle<PropertyDescriptor>,
+) -> bool {
+    assert!(desc.obj.is_null(), "why are we being called?");
+
+    // > 1. If P is `then`, `@@toStringTag`, `@@hasInstance`, or
+    // >    `@@isConcatSpreadable`, then return `PropertyDescriptor{ [[Value]]:
+    // >    undefined, [[Writable]]: false, [[Enumerable]]: false,
+    // >    [[Configurable]]: true }`.
+    if is_cross_origin_allowlisted_prop(cx, id) {
+        *desc = PropertyDescriptor {
+            getter: None,
+            setter: None,
+            value: UndefinedValue(),
+            attrs: jsapi::JSPROP_READONLY as u32,
+            obj: proxy.get(),
+        };
+        return true;
+    }
+
+    // > 2. Throw a `SecurityError` `DOMException`.
+    report_cross_origin_denial(cx, id, "access")
+}
+
+unsafe fn is_cross_origin_allowlisted_prop(cx: SafeJSContext, id: RawHandleId) -> bool {
+    const ALLOWLISTED_SYMBOL_CODES: &[SymbolCode] = &[
+        SymbolCode::toStringTag,
+        SymbolCode::hasInstance,
+        SymbolCode::isConcatSpreadable,
+    ];
+
+    crate::dom::bindings::conversions::jsid_to_string(*cx, Handle::from_raw(id))
+        .filter(|st| st == "then")
+        .is_some() ||
+        {
+            rooted!(in(*cx) let mut allowed_id: jsid);
+            ALLOWLISTED_SYMBOL_CODES.iter().any(|&allowed_code| {
+                RUST_SYMBOL_TO_JSID(
+                    GetWellKnownSymbol(*cx, allowed_code),
+                    allowed_id.handle_mut().into(),
+                );
+                // `jsid`s containing `JS::Symbol *` can be compared by
+                // referential equality
+                allowed_id.get().asBits == id.asBits
+            })
+        }
+}
+
+/// Get the holder for cross-origin properties for the current global of the
+/// `JSContext`, creating one and storing it in a slot of the proxy object if it
+/// doesn't exist yet.
+///
+/// This essentially creates a cache of [`CrossOriginGetOwnPropertyHelper`]'s
+/// results for all property keys.
+///
+/// [`CrossOriginGetOwnPropertyHelper`]: https://html.spec.whatwg.org/multipage/#crossorigingetownpropertyhelper-(-o,-p-)
+unsafe fn ensure_cross_origin_property_holder(
+    cx: SafeJSContext,
+    _proxy: RawHandleObject,
+    cross_origin_properties: &'static CrossOriginProperties,
+    out_holder: RawMutableHandleObject,
+) -> bool {
+    // TODO: We don't have the slot to store the holder yet. For now,
+    //       the holder is constructed every time this function is called,
+    //       which is not only inefficient but also deviates from the
+    //       specification in a subtle yet observable way.
+
+    // Create a holder for the current Realm
+    out_holder.set(jsapi::JS_NewObjectWithGivenProto(
+        *cx,
+        ptr::null_mut(),
+        RawHandleObject::null(),
+    ));
+
+    if out_holder.get().is_null() ||
+        !jsapi::JS_DefineProperties(
+            *cx,
+            out_holder.handle(),
+            cross_origin_properties.attributes.as_ptr(),
+        ) ||
+        !jsapi::JS_DefineFunctions(
+            *cx,
+            out_holder.handle(),
+            cross_origin_properties.methods.as_ptr(),
+        )
+    {
+        return false;
+    }
+
+    // TODO: Store the holder in the slot that we don't have yet.
+
+    true
+}