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LibJS: Bring ForIn body evaluation closer to the specification

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This fixes 2 bugs in our current implementation:
 * Properties deleted during iteration were still being iterated
 * Properties with the same name in both the object and it's prototype
   were iterated twice
This commit is contained in:
Idan Horowitz 2022-03-29 00:18:39 +03:00
parent 9cfbbfd8d8
commit 02e97b3313
2 changed files with 40 additions and 20 deletions
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39
Userland/Libraries/LibJS/AST.cpp
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@ -1021,30 +1021,29 @@ Completion ForInStatement::loop_evaluation(Interpreter& interpreter, GlobalObjec
// 3. Let V be undefined.
auto last_value = js_undefined();
while (object) {
auto property_names = TRY(object->enumerable_own_property_names(Object::PropertyKind::Key));
for (auto& value : property_names) {
TRY(for_in_head_state.execute_head(interpreter, global_object, value));
auto result = object->enumerate_object_properties([&](auto value) -> Optional<Completion> {
TRY(for_in_head_state.execute_head(interpreter, global_object, value));
// l. Let result be the result of evaluating stmt.
auto result = m_body->execute(interpreter, global_object);
// l. Let result be the result of evaluating stmt.
auto result = m_body->execute(interpreter, global_object);
// m. Set the running execution context's LexicalEnvironment to oldEnv.
interpreter.vm().running_execution_context().lexical_environment = old_environment;
// m. Set the running execution context's LexicalEnvironment to oldEnv.
interpreter.vm().running_execution_context().lexical_environment = old_environment;
// n. If LoopContinues(result, labelSet) is false, then
if (!loop_continues(result, label_set)) {
// 1. Return Completion(UpdateEmpty(result, V)).
return result.update_empty(last_value);
}
// o. If result.[[Value]] is not empty, set V to result.[[Value]].
if (result.value().has_value())
last_value = *result.value();
// n. If LoopContinues(result, labelSet) is false, then
if (!loop_continues(result, label_set)) {
// 1. Return Completion(UpdateEmpty(result, V)).
return result.update_empty(last_value);
}
object = TRY(object->internal_get_prototype_of());
}
return last_value;
// o. If result.[[Value]] is not empty, set V to result.[[Value]].
if (result.value().has_value())
last_value = *result.value();
return {};
});
return result.value_or(last_value);
}
// 14.1.1 Runtime Semantics: Evaluation, https://tc39.es/ecma262/#sec-statement-semantics-runtime-semantics-evaluation