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LibJS: Implement spec-compliant OrdinaryToPrimitive

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This renames Object::to_primitive() to Object::ordinary_to_primitive()
for two reasons:

- No confusion with Value::to_primitive()
- To match the spec's name

Also change existing uses of Object::to_primitive() to
Value::to_primitive() when the spec uses the latter (which will still
call Object::ordinary_to_primitive()). Object::to_string() has been
removed as it's not needed anymore (and nothing the spec uses).

This makes it possible to overwrite an object's toString and valueOf and
have them provide results for anything that uses to_primitive() - e.g.:

    const o = { toString: undefined, valueOf: () => 42 };
    Number(o) // 42, previously NaN
    ["foo", o].toString(); // "foo,42", previously "foo,[object Object]"
    ++o // 43, previously NaN

etc.
This commit is contained in:
Linus Groh 2020-11-03 19:52:21 +00:00 • committed by Andreas Kling
parent e163db248d
commit fb89c324c5
4 changed files with 50 additions and 42 deletions
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54
Libraries/LibJS/Runtime/Object.cpp
View file

@ -836,48 +836,30 @@ bool Object::has_own_property(const PropertyName& property_name) const
return shape().lookup(property_name.to_string_or_symbol()).has_value();
}
Value Object::to_primitive(Value::PreferredType preferred_type) const
Value Object::ordinary_to_primitive(Value::PreferredType preferred_type) const
{
Value result = js_undefined();
ASSERT(preferred_type == Value::PreferredType::String || preferred_type == Value::PreferredType::Number);
switch (preferred_type) {
case Value::PreferredType::Default:
case Value::PreferredType::Number: {
result = value_of();
if (result.is_object()) {
result = to_string();
}
break;
}
case Value::PreferredType::String: {
result = to_string();
if (result.is_object())
result = value_of();
break;
}
}
ASSERT(!result.is_object());
return result;
}
Value Object::to_string() const
{
auto& vm = this->vm();
auto to_string_property = get(vm.names.toString);
if (to_string_property.is_function()) {
auto& to_string_function = to_string_property.as_function();
auto to_string_result = vm.call(to_string_function, const_cast<Object*>(this));
if (to_string_result.is_object())
vm.throw_exception<TypeError>(global_object(), ErrorType::Convert, "object", "string");
Vector<FlyString, 2> method_names;
if (preferred_type == Value::PreferredType::String)
method_names = { vm.names.toString, vm.names.valueOf };
else
method_names = { vm.names.valueOf, vm.names.toString };
for (auto& method_name : method_names) {
auto method = get(method_name);
if (vm.exception())
return {};
auto* string = to_string_result.to_primitive_string(global_object());
if (vm.exception())
return {};
return string;
if (method.is_function()) {
auto result = vm.call(method.as_function(), const_cast<Object*>(this));
if (!result.is_object())
return result;
}
}
return js_string(vm, String::formatted("[object {}]", class_name()));
vm.throw_exception<TypeError>(global_object(), ErrorType::Convert, "object", preferred_type == Value::PreferredType::String ? "string" : "number");
return {};
}
Value Object::invoke(const StringOrSymbol& property_name, Optional<MarkedValueList> arguments)