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LibJS: Implement basic support for the "delete" operator

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It turns out "delete" is actually a unary op :)
This patch implements deletion of object properties, it doesn't yet
work for casually deleting properties from the global object.

When deleting a property from an object, we switch that object to
having a unique shape, no longer sharing shapes with others.
Once an object has a unique shape, it no longer needs to care about
shape transitions.
This commit is contained in:
Andreas Kling 2020-04-26 13:53:40 +02:00
parent 1617be1e6f
commit f897c41092
9 changed files with 190 additions and 8 deletions
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51
Libraries/LibJS/Runtime/Object.cpp
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@ -71,6 +71,10 @@ void Object::set_prototype(Object* new_prototype)
{
if (prototype() == new_prototype)
return;
if (shape().is_unique()) {
shape().set_prototype_without_transition(new_prototype);
return;
}
m_shape = m_shape->create_prototype_transition(new_prototype);
}
@ -113,8 +117,11 @@ void Object::put_own_property(Object& this_object, const FlyString& property_nam
{
auto metadata = shape().lookup(property_name);
if (!metadata.has_value()) {
auto* new_shape = m_shape->create_put_transition(property_name, attributes);
set_shape(*new_shape);
if (m_shape->is_unique()) {
m_shape->add_property_to_unique_shape(property_name, attributes);
} else {
set_shape(*m_shape->create_put_transition(property_name, attributes));
}
metadata = shape().lookup(property_name);
ASSERT(metadata.has_value());
}
@ -126,8 +133,11 @@ void Object::put_own_property(Object& this_object, const FlyString& property_nam
}
if (mode == PutOwnPropertyMode::DefineProperty && attributes != metadata.value().attributes) {
auto* new_shape = m_shape->create_configure_transition(property_name, attributes);
set_shape(*new_shape);
if (m_shape->is_unique()) {
m_shape->reconfigure_property_in_unique_shape(property_name, attributes);
} else {
set_shape(*m_shape->create_configure_transition(property_name, attributes));
}
metadata = shape().lookup(property_name);
dbg() << "Reconfigured property " << property_name << ", new shape says offset is " << metadata.value().offset << " and my storage capacity is " << m_storage.size();
@ -154,6 +164,39 @@ void Object::put_own_property(Object& this_object, const FlyString& property_nam
}
}
Value Object::delete_property(PropertyName property_name)
{
ASSERT(property_name.is_valid());
if (property_name.is_number()) {
if (property_name.as_number() < static_cast<i32>(elements().size())) {
elements()[property_name.as_number()] = {};
return Value(true);
}
return Value(true);
}
auto metadata = shape().lookup(property_name.as_string());
if (!metadata.has_value())
return Value(true);
if (!(metadata.value().attributes & Attribute::Configurable))
return Value(false);
size_t deleted_offset = metadata.value().offset;
ensure_shape_is_unique();
shape().remove_property_from_unique_shape(property_name.as_string(), deleted_offset);
m_storage.remove(deleted_offset);
return Value(true);
}
void Object::ensure_shape_is_unique()
{
if (shape().is_unique())
return;
m_shape = m_shape->create_unique_clone();
}
Value Object::get_by_index(i32 property_index) const
{
if (property_index < 0)