LibJS: Add a global "Object" constructor

This patch adds an "Object" constructor to the global object. The only
function it implements so far is Object.getPrototypeOf().

Libraries/LibJS/Interpreter.cpp

@@ -42,11 +42,12 @@ namespace JS {
 Interpreter::Interpreter()
     : m_heap(*this)
 {
-    m_global_object = heap().allocate<GlobalObject>();
     m_object_prototype = heap().allocate<ObjectPrototype>();
     m_string_prototype = heap().allocate<StringPrototype>();
     m_array_prototype = heap().allocate<ArrayPrototype>();
     m_error_prototype = heap().allocate<ErrorPrototype>();
+
+    m_global_object = heap().allocate<GlobalObject>();
 }
 
 Interpreter::~Interpreter()

Libraries/LibJS/Makefile

@@ -19,6 +19,7 @@ OBJS = \
     Runtime/NativeFunction.o \
     Runtime/NativeProperty.o \
     Runtime/Object.o \
+    Runtime/ObjectConstructor.o \
     Runtime/ObjectPrototype.o \
     Runtime/PrimitiveString.o \
     Runtime/ScriptFunction.o \

Libraries/LibJS/Runtime/GlobalObject.cpp

@@ -6,6 +6,7 @@
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/MathObject.h>
 #include <LibJS/Runtime/NativeFunction.h>
+#include <LibJS/Runtime/ObjectConstructor.h>
 #include <LibJS/Runtime/Value.h>
 
 namespace JS {
@@ -24,6 +25,7 @@ GlobalObject::GlobalObject()
         return Value(arguments[0].to_number().is_nan());
     });
     put("Math", heap().allocate<MathObject>());
+    put("Object", heap().allocate<ObjectConstructor>());
 }
 
 GlobalObject::~GlobalObject()

Libraries/LibJS/Runtime/NativeFunction.h

@@ -31,13 +31,16 @@
 
 namespace JS {
 
-class NativeFunction final : public Function {
+class NativeFunction : public Function {
 public:
     explicit NativeFunction(AK::Function<Value(Object*, const Vector<Value>&)>);
     virtual ~NativeFunction() override;
 
     virtual Value call(Interpreter&, const Vector<Value>&) override;
 
+protected:
+    NativeFunction() {}
+
 private:
     virtual bool is_native_function() const override { return true; }
     virtual const char* class_name() const override { return "NativeFunction"; }

Libraries/LibJS/Runtime/ObjectConstructor.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/ObjectConstructor.h>
+
+namespace JS {
+
+ObjectConstructor::ObjectConstructor()
+{
+    put("prototype", interpreter().object_prototype());
+
+    put_native_function("getPrototypeOf", [this](Object*, const Vector<Value>& arguments) -> Value {
+        if (arguments.size() < 1)
+            return {};
+        auto object = arguments[0].to_object(heap());
+        if (interpreter().exception())
+            return {};
+        if (!object.is_object())
+            return {};
+        return object.as_object()->prototype();
+    });
+}
+
+ObjectConstructor::~ObjectConstructor()
+{
+}
+
+Value ObjectConstructor::call(Interpreter& interpreter, const Vector<Value>&)
+{
+    return interpreter.heap().allocate<Object>();
+}
+
+}

Libraries/LibJS/Runtime/ObjectConstructor.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/NativeFunction.h>
+
+namespace JS {
+
+class ObjectConstructor final : public NativeFunction {
+public:
+    ObjectConstructor();
+    virtual ~ObjectConstructor() override;
+
+    virtual Value call(Interpreter&, const Vector<Value>&) override;
+
+private:
+    virtual const char* class_name() const override { return "ObjectConstructor"; }
+};
+
+}

Libraries/LibJS/Runtime/Value.h

@@ -79,7 +79,7 @@ public:
     }
 
     Value(Object* object)
-        : m_type(Type::Object)
+        : m_type(object ? Type::Object : Type::Null)
     {
         m_value.as_object = object;
     }

Libraries/LibJS/Tests/Object.getPrototypeOf.js

@@ -0,0 +1,11 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var o1 = new Object();
+    var o2 = {};
+    assert(Object.getPrototypeOf(o1) === Object.getPrototypeOf(o2));
+    assert(Object.getPrototypeOf(Object.getPrototypeOf(o1)) === null);
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}

Libraries/LibJS/Tests/Object.prototype.js

@@ -0,0 +1,10 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var o = new Object();
+    Object.prototype.foo = 123;
+    assert(o.foo === 123);
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}