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[JSC] Let an embedder allow a Proxy in the prototype chain of its global object #626

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[JSC] Let an embedder allow a Proxy in the prototype chain of its global object #626

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13 changes: 13 additions & 0 deletions Source/JavaScriptCore/runtime/JSGlobalObject.h
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Original file line number Diff line number Diff line change
Expand Up @@ -691,6 +691,9 @@ class JSGlobalObject : public JSSegmentedVariableObject {
bool m_webAssemblyEnabled { true };
bool m_needsSiteSpecificQuirks { false };
bool m_canDoASCIIUCADUCETLocaleCompare { false };
#if USE(BUN_JSC_ADDITIONS)
bool m_allowsProxyInPrototypeChain { false };
#endif
unsigned m_globalLexicalBindingEpoch { 1 };
String m_evalDisabledErrorMessage;
String m_webAssemblyDisabledErrorMessage;
Expand Down Expand Up @@ -1348,6 +1351,16 @@ class JSGlobalObject : public JSSegmentedVariableObject {
bool needsSiteSpecificQuirks() const { return m_needsSiteSpecificQuirks; }
JS_EXPORT_PRIVATE void exposeDollarVM(VM&);

#if USE(BUN_JSC_ADDITIONS)
// A global object is normally an immutable prototype exotic object, so a Proxy can never reach its
// prototype chain, and ProgramExecutable::initializeGlobalProperties rejects a chain that holds one.
// An embedder whose global object has a mutable prototype (node:vm contexts, where jsdom installs a
// Proxy in the chain of the window) opts out of that rejection here. Global declaration instantiation
// only reads own properties of the global object, so no Proxy trap runs while a program links.
bool allowsProxyInPrototypeChain() const { return m_allowsProxyInPrototypeChain; }
void setAllowsProxyInPrototypeChain(bool allows) { m_allowsProxyInPrototypeChain = allows; }
#endif

#if JSC_OBJC_API_ENABLED
JSWrapperMap* wrapperMap() const { return m_wrapperMap.get(); }
void setWrapperMap(JSWrapperMap* map) { m_wrapperMap = map; }
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17 changes: 12 additions & 5 deletions Source/JavaScriptCore/runtime/ProgramExecutable.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -117,11 +117,18 @@ JSObject* ProgramExecutable::initializeGlobalProperties(VM& vm, JSGlobalObject*
if (error.isValid())
RELEASE_AND_RETURN(throwScope, error.toErrorObject(globalObject, source()));

JSValue nextPrototype = globalObject->getPrototypeDirect();
while (nextPrototype && nextPrototype.isObject()) {
if (asObject(nextPrototype)->type() == ProxyObjectType) [[unlikely]]
return createTypeError(globalObject, "Proxy is not allowed in the global prototype chain."_s);
nextPrototype = asObject(nextPrototype)->getPrototypeDirect();
#if USE(BUN_JSC_ADDITIONS)
bool rejectProxyInPrototypeChain = !globalObject->allowsProxyInPrototypeChain();
#else
bool rejectProxyInPrototypeChain = true;
#endif
if (rejectProxyInPrototypeChain) {
JSValue nextPrototype = globalObject->getPrototypeDirect();
while (nextPrototype && nextPrototype.isObject()) {
if (asObject(nextPrototype)->type() == ProxyObjectType) [[unlikely]]
return createTypeError(globalObject, "Proxy is not allowed in the global prototype chain."_s);
nextPrototype = asObject(nextPrototype)->getPrototypeDirect();
}
}

JSGlobalLexicalEnvironment* globalLexicalEnvironment = globalObject->globalLexicalEnvironment();
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