path: root/js/src/proxy/BaseProxyHandler.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "js/Proxy.h"
#include "vm/ProxyObject.h"

#include "jscntxtinlines.h"
#include "jsobjinlines.h"

using namespace js;

using JS::IsArrayAnswer;

bool
BaseProxyHandler::enter(JSContext* cx, HandleObject wrapper, HandleId id, Action act,
                        bool* bp) const
{
    *bp = true;
    return true;
}

bool
BaseProxyHandler::has(JSContext* cx, HandleObject proxy, HandleId id, bool* bp) const
{
    assertEnteredPolicy(cx, proxy, id, GET);

    // This method is not covered by any spec, but we follow ES 2016
    // (February 11, 2016) 9.1.7.1 fairly closely.

    // Step 2. (Step 1 is a superfluous assertion.)
    // Non-standard: Use our faster hasOwn trap.
    if (!hasOwn(cx, proxy, id, bp))
        return false;

    // Step 3.
    if (*bp)
        return true;

    // The spec calls this variable "parent", but that word has weird
    // connotations in SpiderMonkey, so let's go with "proto".
    // Step 4.
    RootedObject proto(cx);
    if (!GetPrototype(cx, proxy, &proto))
        return false;

    // Step 5.,5.a.
    if (proto)
        return HasProperty(cx, proto, id, bp);

    // Step 6.
    *bp = false;
    return true;
}

bool
BaseProxyHandler::getPropertyDescriptor(JSContext* cx, HandleObject proxy, HandleId id,
                                        MutableHandle<PropertyDescriptor> desc) const
{
    assertEnteredPolicy(cx, proxy, id, GET | SET | GET_PROPERTY_DESCRIPTOR);

    if (!getOwnPropertyDescriptor(cx, proxy, id, desc))
        return false;
    if (desc.object())
        return true;

    RootedObject proto(cx);
    if (!GetPrototype(cx, proxy, &proto))
        return false;
    if (!proto) {
        MOZ_ASSERT(!desc.object());
        return true;
    }
    return GetPropertyDescriptor(cx, proto, id, desc);
}


bool
BaseProxyHandler::hasOwn(JSContext* cx, HandleObject proxy, HandleId id, bool* bp) const
{
    assertEnteredPolicy(cx, proxy, id, GET);
    Rooted<PropertyDescriptor> desc(cx);
    if (!getOwnPropertyDescriptor(cx, proxy, id, &desc))
        return false;
    *bp = !!desc.object();
    return true;
}

bool
BaseProxyHandler::get(JSContext* cx, HandleObject proxy, HandleValue receiver,
                      HandleId id, MutableHandleValue vp) const
{
    assertEnteredPolicy(cx, proxy, id, GET);

    // This method is not covered by any spec, but we follow ES 2016
    // (January 21, 2016) 9.1.8 fairly closely.

    // Step 2. (Step 1 is a superfluous assertion.)
    Rooted<PropertyDescriptor> desc(cx);
    if (!getOwnPropertyDescriptor(cx, proxy, id, &desc))
        return false;
    desc.assertCompleteIfFound();

    // Step 3.
    if (!desc.object()) {
        // The spec calls this variable "parent", but that word has weird
        // connotations in SpiderMonkey, so let's go with "proto".
        // Step 3.a.
        RootedObject proto(cx);
        if (!GetPrototype(cx, proxy, &proto))
            return false;

        // Step 3.b.
        if (!proto) {
            vp.setUndefined();
            return true;
        }

        // Step 3.c.
        return GetProperty(cx, proto, receiver, id, vp);
    }

    // Step 4.
    if (desc.isDataDescriptor()) {
        vp.set(desc.value());
        return true;
    }

    // Step 5.
    MOZ_ASSERT(desc.isAccessorDescriptor());
    RootedObject getter(cx, desc.getterObject());

    // Step 6.
    if (!getter) {
        vp.setUndefined();
        return true;
    }

    // Step 7.
    RootedValue getterFunc(cx, ObjectValue(*getter));
    return CallGetter(cx, receiver, getterFunc, vp);
}

bool
BaseProxyHandler::set(JSContext* cx, HandleObject proxy, HandleId id, HandleValue v,
                      HandleValue receiver, ObjectOpResult& result) const
{
    assertEnteredPolicy(cx, proxy, id, SET);

    // This method is not covered by any spec, but we follow ES6 draft rev 28
    // (2014 Oct 14) 9.1.9 fairly closely, adapting it slightly for
    // SpiderMonkey's particular foibles.

    // Steps 2-3.  (Step 1 is a superfluous assertion.)
    Rooted<PropertyDescriptor> ownDesc(cx);
    if (!getOwnPropertyDescriptor(cx, proxy, id, &ownDesc))
        return false;
    ownDesc.assertCompleteIfFound();

    // The rest is factored out into a separate function with a weird name.
    // This algorithm continues just below.
    return SetPropertyIgnoringNamedGetter(cx, proxy, id, v, receiver, ownDesc, result);
}

bool
js::SetPropertyIgnoringNamedGetter(JSContext* cx, HandleObject obj, HandleId id, HandleValue v,
                                   HandleValue receiver, Handle<PropertyDescriptor> ownDesc_,
                                   ObjectOpResult& result)
{
    Rooted<PropertyDescriptor> ownDesc(cx, ownDesc_);

    // Step 4.
    if (!ownDesc.object()) {
        // The spec calls this variable "parent", but that word has weird
        // connotations in SpiderMonkey, so let's go with "proto".
        RootedObject proto(cx);
        if (!GetPrototype(cx, obj, &proto))
            return false;
        if (proto)
            return SetProperty(cx, proto, id, v, receiver, result);

        // Step 4.d.
        ownDesc.setDataDescriptor(UndefinedHandleValue, JSPROP_ENUMERATE);
    }

    // Step 5.
    if (ownDesc.isDataDescriptor()) {
        // Steps 5.a-b.
        if (!ownDesc.writable())
            return result.fail(JSMSG_READ_ONLY);
        if (!receiver.isObject())
            return result.fail(JSMSG_SET_NON_OBJECT_RECEIVER);
        RootedObject receiverObj(cx, &receiver.toObject());

        // Nonstandard SpiderMonkey special case: setter ops.
        SetterOp setter = ownDesc.setter();
        MOZ_ASSERT(setter != JS_StrictPropertyStub);
        if (setter && setter != JS_StrictPropertyStub) {
            RootedValue valCopy(cx, v);
            return CallJSSetterOp(cx, setter, receiverObj, id, &valCopy, result);
        }

        // Steps 5.c-d.
        Rooted<PropertyDescriptor> existingDescriptor(cx);
        if (!GetOwnPropertyDescriptor(cx, receiverObj, id, &existingDescriptor))
            return false;

        // Step 5.e.
        if (existingDescriptor.object()) {
            // Step 5.e.i.
            if (existingDescriptor.isAccessorDescriptor())
                return result.fail(JSMSG_OVERWRITING_ACCESSOR);

            // Step 5.e.ii.
            if (!existingDescriptor.writable())
                return result.fail(JSMSG_READ_ONLY);
        }


        // Steps 5.e.iii-iv. and 5.f.i.
        unsigned attrs =
            existingDescriptor.object()
            ? JSPROP_IGNORE_ENUMERATE | JSPROP_IGNORE_READONLY | JSPROP_IGNORE_PERMANENT
            : JSPROP_ENUMERATE;

        // A very old nonstandard SpiderMonkey extension: default to the Class
        // getter and setter ops.
        const Class* clasp = receiverObj->getClass();
        MOZ_ASSERT(clasp->getGetProperty() != JS_PropertyStub);
        MOZ_ASSERT(clasp->getSetProperty() != JS_StrictPropertyStub);
        return DefineProperty(cx, receiverObj, id, v,
                              clasp->getGetProperty(), clasp->getSetProperty(), attrs, result);
    }

    // Step 6.
    MOZ_ASSERT(ownDesc.isAccessorDescriptor());
    RootedObject setter(cx);
    if (ownDesc.hasSetterObject())
        setter = ownDesc.setterObject();
    if (!setter)
        return result.fail(JSMSG_GETTER_ONLY);
    RootedValue setterValue(cx, ObjectValue(*setter));
    if (!CallSetter(cx, receiver, setterValue, v))
        return false;
    return result.succeed();
}

bool
BaseProxyHandler::getOwnEnumerablePropertyKeys(JSContext* cx, HandleObject proxy,
                                               AutoIdVector& props) const
{
    assertEnteredPolicy(cx, proxy, JSID_VOID, ENUMERATE);
    MOZ_ASSERT(props.length() == 0);

    if (!ownPropertyKeys(cx, proxy, props))
        return false;

    /* Select only the enumerable properties through in-place iteration. */
    RootedId id(cx);
    size_t i = 0;
    for (size_t j = 0, len = props.length(); j < len; j++) {
        MOZ_ASSERT(i <= j);
        id = props[j];
        if (JSID_IS_SYMBOL(id))
            continue;

        AutoWaivePolicy policy(cx, proxy, id, BaseProxyHandler::GET);
        Rooted<PropertyDescriptor> desc(cx);
        if (!getOwnPropertyDescriptor(cx, proxy, id, &desc))
            return false;
        desc.assertCompleteIfFound();

        if (desc.object() && desc.enumerable())
            props[i++].set(id);
    }

    MOZ_ASSERT(i <= props.length());
    if (!props.resize(i))
        return false;

    return true;
}

bool
BaseProxyHandler::enumerate(JSContext* cx, HandleObject proxy, MutableHandleObject objp) const
{
    assertEnteredPolicy(cx, proxy, JSID_VOID, ENUMERATE);

    // GetPropertyKeys will invoke getOwnEnumerablePropertyKeys along the proto
    // chain for us.
    AutoIdVector props(cx);
    if (!GetPropertyKeys(cx, proxy, 0, &props))
        return false;

    return EnumeratedIdVectorToIterator(cx, proxy, 0, props, objp);
}

bool
BaseProxyHandler::call(JSContext* cx, HandleObject proxy, const CallArgs& args) const
{
    MOZ_CRASH("callable proxies should implement call trap");
}

bool
BaseProxyHandler::construct(JSContext* cx, HandleObject proxy, const CallArgs& args) const
{
    MOZ_CRASH("callable proxies should implement construct trap");
}

const char*
BaseProxyHandler::className(JSContext* cx, HandleObject proxy) const
{
    return proxy->isCallable() ? "Function" : "Object";
}

JSString*
BaseProxyHandler::fun_toString(JSContext* cx, HandleObject proxy, unsigned indent) const
{
    if (proxy->isCallable())
        return JS_NewStringCopyZ(cx, "function () {\n    [native code]\n}");
    RootedValue v(cx, ObjectValue(*proxy));
    ReportIsNotFunction(cx, v);
    return nullptr;
}

bool
BaseProxyHandler::regexp_toShared(JSContext* cx, HandleObject proxy,
                                  RegExpGuard* g) const
{
    MOZ_CRASH("This should have been a wrapped regexp");
}

bool
BaseProxyHandler::boxedValue_unbox(JSContext* cx, HandleObject proxy, MutableHandleValue vp) const
{
    vp.setUndefined();
    return true;
}

bool
BaseProxyHandler::nativeCall(JSContext* cx, IsAcceptableThis test, NativeImpl impl,
                             const CallArgs& args) const
{
    ReportIncompatible(cx, args);
    return false;
}

bool
BaseProxyHandler::hasInstance(JSContext* cx, HandleObject proxy, MutableHandleValue v,
                              bool* bp) const
{
    assertEnteredPolicy(cx, proxy, JSID_VOID, GET);
    RootedValue val(cx, ObjectValue(*proxy.get()));
    ReportValueError(cx, JSMSG_BAD_INSTANCEOF_RHS,
                     JSDVG_SEARCH_STACK, val, nullptr);
    return false;
}

bool
BaseProxyHandler::getBuiltinClass(JSContext* cx, HandleObject proxy, ESClass* cls) const
{
    *cls = ESClass::Other;
    return true;
}

bool
BaseProxyHandler::isArray(JSContext* cx, HandleObject proxy, IsArrayAnswer* answer) const
{
    *answer = IsArrayAnswer::NotArray;
    return true;
}

void
BaseProxyHandler::trace(JSTracer* trc, JSObject* proxy) const
{
}

void
BaseProxyHandler::finalize(JSFreeOp* fop, JSObject* proxy) const
{
}

void
BaseProxyHandler::objectMoved(JSObject* proxy, const JSObject* old) const
{
}

JSObject*
BaseProxyHandler::weakmapKeyDelegate(JSObject* proxy) const
{
    return nullptr;
}

bool
BaseProxyHandler::getPrototype(JSContext* cx, HandleObject proxy, MutableHandleObject protop) const
{
    MOZ_CRASH("must override getPrototype with dynamic prototype");
}

bool
BaseProxyHandler::setPrototype(JSContext* cx, HandleObject proxy, HandleObject proto,
                               ObjectOpResult& result) const
{
    // Disallow sets of protos on proxies with dynamic prototypes but no hook.
    // This keeps us away from the footgun of having the first proto set opt
    // you out of having dynamic protos altogether.
    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_SET_PROTO_OF,
                              "incompatible Proxy");
    return false;
}

bool
BaseProxyHandler::setImmutablePrototype(JSContext* cx, HandleObject proxy, bool* succeeded) const
{
    *succeeded = false;
    return true;
}

bool
BaseProxyHandler::getElements(JSContext* cx, HandleObject proxy, uint32_t begin, uint32_t end,
                              ElementAdder* adder) const
{
    assertEnteredPolicy(cx, proxy, JSID_VOID, GET);

    return js::GetElementsWithAdder(cx, proxy, proxy, begin, end, adder);
}

bool
BaseProxyHandler::isCallable(JSObject* obj) const
{
    return false;
}

bool
BaseProxyHandler::isConstructor(JSObject* obj) const
{
    return false;
}