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

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() :^)

1 files changed, 44 insertions, 2 deletions

diff --git a/Libraries/LibJS/Runtime/ObjectConstructor.cpp b/Libraries/LibJS/Runtime/ObjectConstructor.cpp
index bef6ceff1e..5d3b54fdfb 100644
--- a/Libraries/LibJS/Runtime/ObjectConstructor.cpp
+++ b/Libraries/LibJS/Runtime/ObjectConstructor.cpp
@@ -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;
+}
+
 }