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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
Notes: sideshowbarker 2024-07-19 07:45:53 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/e6d920d87dd
7 changed files with 121 additions and 16 deletions
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46
Libraries/LibJS/Runtime/ObjectConstructor.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/ObjectConstructor.h>
#include <LibJS/Runtime/Shape.h>
@@ -37,6 +38,8 @@ ObjectConstructor::ObjectConstructor()
{
put("prototype", interpreter().object_prototype());
put_native_function("defineProperty", define_property, 3);
put_native_function("getOwnPropertyDescriptor", get_own_property_descriptor, 2);
put_native_function("getOwnPropertyNames", get_own_property_names, 1);
put_native_function("getPrototypeOf", get_prototype_of, 1);
put_native_function("setPrototypeOf", set_prototype_of, 2);
@@ -88,8 +91,6 @@ Value ObjectConstructor::set_prototype_of(Interpreter& interpreter)
{
if (interpreter.argument_count() < 2)
return {};
if (!interpreter.argument(0).is_object())
return {};
auto* object = interpreter.argument(0).to_object(interpreter.heap());
if (interpreter.exception())
return {};
@@ -97,4 +98,45 @@ Value ObjectConstructor::set_prototype_of(Interpreter& interpreter)
return {};
}
Value ObjectConstructor::get_own_property_descriptor(Interpreter& interpreter)
{
if (interpreter.argument_count() < 2)
return interpreter.throw_exception<Error>("TypeError", "Object.getOwnPropertyDescriptor() needs 2 arguments");
if (!interpreter.argument(0).is_object())
return interpreter.throw_exception<Error>("TypeError", "Object argument is not an object");
auto& object = interpreter.argument(0).as_object();
auto metadata = object.shape().lookup(interpreter.argument(1).to_string());
if (!metadata.has_value())
return js_undefined();
auto* descriptor = interpreter.heap().allocate<Object>();
descriptor->put("configurable", Value(!!(metadata.value().attributes & Attribute::Configurable)));
descriptor->put("enumerable", Value(!!(metadata.value().attributes & Attribute::Enumerable)));
descriptor->put("writable", Value(!!(metadata.value().attributes & Attribute::Writable)));
descriptor->put("value", object.get(interpreter.argument(1).to_string()).value_or(js_undefined()));
return descriptor;
}
Value ObjectConstructor::define_property(Interpreter& interpreter)
{
if (interpreter.argument_count() < 3)
return interpreter.throw_exception<Error>("TypeError", "Object.defineProperty() needs 3 arguments");
if (!interpreter.argument(0).is_object())
return interpreter.throw_exception<Error>("TypeError", "Object argument is not an object");
if (!interpreter.argument(2).is_object())
return interpreter.throw_exception<Error>("TypeError", "Descriptor argument is not an object");
auto& object = interpreter.argument(0).as_object();
auto& descriptor = interpreter.argument(2).as_object();
Value value = descriptor.get("value").value_or(js_undefined());
u8 configurable = descriptor.get("configurable").value_or(Value(false)).to_boolean() * Attribute::Configurable;
u8 enumerable = descriptor.get("enumerable").value_or(Value(false)).to_boolean() * Attribute::Enumerable;
u8 writable = descriptor.get("writable").value_or(Value(false)).to_boolean() * Attribute::Writable;
u8 attributes = configurable | enumerable | writable;
dbg() << "Defining new property " << interpreter.argument(1).to_string() << " with descriptor { " << configurable << ", " << enumerable << ", " << writable << ", attributes=" << attributes << " }";
object.put_own_property(object, interpreter.argument(1).to_string(), attributes, value, PutOwnPropertyMode::DefineProperty);
return &object;
}
}