LibJS: Add AsyncIteratorPrototype

Userland/Libraries/LibJS/CMakeLists.txt

@@ -43,6 +43,7 @@ set(SOURCES
     Runtime/AsyncFunctionPrototype.cpp
     Runtime/AsyncGeneratorFunctionConstructor.cpp
     Runtime/AsyncGeneratorFunctionPrototype.cpp
+    Runtime/AsyncIteratorPrototype.cpp
     Runtime/AtomicsObject.cpp
     Runtime/BigInt.cpp
     Runtime/BigIntConstructor.cpp

Userland/Libraries/LibJS/Forward.h

@@ -88,6 +88,7 @@
 #define JS_ENUMERATE_ITERATOR_PROTOTYPES                         \
     __JS_ENUMERATE(Iterator, iterator)                           \
     __JS_ENUMERATE(ArrayIterator, array_iterator)                \
+    __JS_ENUMERATE(AsyncIterator, async_iterator)                \
     __JS_ENUMERATE(MapIterator, map_iterator)                    \
     __JS_ENUMERATE(RegExpStringIterator, regexp_string_iterator) \
     __JS_ENUMERATE(SetIterator, set_iterator)                    \

Userland/Libraries/LibJS/Runtime/AsyncIteratorPrototype.cpp

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2021, David Tuin <davidot@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/AsyncIteratorPrototype.h>
+
+namespace JS {
+
+AsyncIteratorPrototype::AsyncIteratorPrototype(GlobalObject& global_object)
+    : Object(*global_object.object_prototype())
+{
+}
+
+void AsyncIteratorPrototype::initialize(GlobalObject& global_object)
+{
+    auto& vm = this->vm();
+    Object::initialize(global_object);
+    u8 attr = Attribute::Writable | Attribute::Enumerable;
+    define_native_function(*vm.well_known_symbol_async_iterator(), symbol_async_iterator, 0, attr);
+}
+
+// 27.1.3.1 %AsyncIteratorPrototype% [ @@asyncIterator ] ( ), https://tc39.es/ecma262/#sec-asynciteratorprototype-asynciterator
+JS_DEFINE_NATIVE_FUNCTION(AsyncIteratorPrototype::symbol_async_iterator)
+{
+    // 1. Return the this value.
+    return vm.this_value(global_object);
+}
+
+}

Userland/Libraries/LibJS/Runtime/AsyncIteratorPrototype.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2021, David Tuin <davidot@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/PrototypeObject.h>
+
+namespace JS {
+
+class AsyncIteratorPrototype final : public Object {
+    JS_OBJECT(AsyncIteratorPrototype, Object)
+
+public:
+    explicit AsyncIteratorPrototype(GlobalObject&);
+    virtual void initialize(GlobalObject&) override;
+    virtual ~AsyncIteratorPrototype() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(symbol_async_iterator);
+};
+
+}

Userland/Libraries/LibJS/Runtime/GlobalObject.cpp

@@ -24,6 +24,7 @@
 #include <LibJS/Runtime/AsyncFunctionPrototype.h>
 #include <LibJS/Runtime/AsyncGeneratorFunctionConstructor.h>
 #include <LibJS/Runtime/AsyncGeneratorFunctionPrototype.h>
+#include <LibJS/Runtime/AsyncIteratorPrototype.h>
 #include <LibJS/Runtime/AtomicsObject.h>
 #include <LibJS/Runtime/BigIntConstructor.h>
 #include <LibJS/Runtime/BigIntPrototype.h>