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LibJS: Add Object.defineProperty() and start caring about attributes

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We now care (a little bit) about the "configurable" and "writable"
property attributes.

Property attributes are stored together with the property name in
the Shape object. Forward transitions are not attribute-savvy and will
cause poor Shape reuse in the case of multiple same-name properties
with different attributes.

Oh, and this patch also adds Object.getOwnPropertyDescriptor() :^)
This commit is contained in:
Andreas Kling 2020-04-09 22:15:26 +02:00
parent 1570e67881
commit e6d920d87d
7 changed files with 121 additions and 16 deletions
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16
Libraries/LibJS/Runtime/Object.cpp
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@ -28,6 +28,7 @@
#include <LibJS/Heap/Heap.h>
#include <LibJS/Interpreter.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/Error.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/NativeFunction.h>
#include <LibJS/Runtime/NativeProperty.h>
@ -97,14 +98,22 @@ void Object::set_shape(Shape& new_shape)
m_shape = &new_shape;
}
bool Object::put_own_property(Object& this_object, const FlyString& property_name, Value value)
void Object::put_own_property(Object& this_object, const FlyString& property_name, u8 attributes, Value value, PutOwnPropertyMode mode)
{
auto metadata = shape().lookup(property_name);
if (!metadata.has_value()) {
auto* new_shape = m_shape->create_put_transition(property_name, 0);
auto* new_shape = m_shape->create_put_transition(property_name, attributes);
set_shape(*new_shape);
metadata = shape().lookup(property_name);
ASSERT(metadata.has_value());
} else if (!(metadata.value().attributes & Attribute::Writable)) {
dbg() << "Disallow write to non-writable property";
return;
}
if (mode == PutOwnPropertyMode::DefineProperty && !(metadata.value().attributes & Attribute::Configurable) && attributes != metadata.value().attributes) {
dbg() << "Disallow reconfig of non-configurable property";
interpreter().throw_exception<Error>("TypeError", String::format("Cannot redefine property '%s'", property_name.characters()));
return;
}
auto value_here = m_storage[metadata.value().offset];
@ -118,7 +127,6 @@ bool Object::put_own_property(Object& this_object, const FlyString& property_nam
} else {
m_storage[metadata.value().offset] = value;
}
return true;
}
Optional<Value> Object::get_by_index(i32 property_index) const
@ -201,7 +209,7 @@ void Object::put(const FlyString& property_name, Value value)
}
object = object->prototype();
}
put_own_property(*this, property_name, value);
put_own_property(*this, property_name, Attribute::Configurable | Attribute::Enumerable | Attribute::Writable, value, PutOwnPropertyMode::Put);
}
void Object::put(PropertyName property_name, Value value)