[dart2js] Extended structured clone algorithm to JSObject.

Change-Id: I0d8b20184f1b88e4bb24f67c2237b2095370118d
Bug: #37438
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/114043
Commit-Queue: Mayank Patke <[email protected]>
Reviewed-by: Stephen Adams <[email protected]>

Author: fishythefish

sdk/lib/html/html_common/conversions.dart

@@ -76,6 +76,9 @@ abstract class _StructuredClone {
 
   cleanupSlots() {} // Will be needed if we mark objects with a property.
   bool cloneNotRequired(object);
+  JSObject newJsObject();
+  void forEachObjectKey(object, action(key, value));
+  void putIntoObject(object, key, value);
   newJsMap();
   List newJsList(length);
   void putIntoMap(map, key, value);
@@ -134,6 +137,19 @@ abstract class _StructuredClone {
       return copy;
     }
 
+    if (e is JSObject) {
+      var slot = findSlot(e);
+      var copy = readSlot(slot);
+      if (copy != null) return copy;
+      copy = newJsObject();
+      writeSlot(slot, copy);
+      // TODO: Consider inlining this so we don't allocate a closure.
+      forEachObjectKey(e, (key, value) {
+        putIntoObject(copy, key, walk(value));
+      });
+      return copy;
+    }
+
     throw new UnimplementedError('structured clone of other type');
   }
 

sdk/lib/html/html_common/conversions_dart2js.dart

@@ -53,6 +53,18 @@ convertNativeToDart_AcceptStructuredClone(object, {mustCopy: false}) =>
         .convertNativeToDart_AcceptStructuredClone(object, mustCopy: mustCopy);
 
 class _StructuredCloneDart2Js extends _StructuredClone {
+  JSObject newJsObject() => JS('JSObject', '{}');
+
+  void forEachObjectKey(object, action(key, value)) {
+    for (final key
+        in JS('returns:JSExtendableArray;new:true', 'Object.keys(#)', object)) {
+      action(key, JS('var', '#[#]', object, key));
+    }
+  }
+
+  void putIntoObject(object, key, value) =>
+      JS('void', '#[#] = #', object, key, value);
+
   newJsMap() => JS('var', '{}');
   putIntoMap(map, key, value) => JS('void', '#[#] = #', map, key, value);
   newJsList(length) => JS('JSExtendableArray', 'new Array(#)', length);

sdk/lib/html/html_common/html_common_dart2js.dart

@@ -13,7 +13,7 @@ import 'dart:typed_data';
 import 'dart:_native_typed_data';
 import 'dart:_js_helper' show Creates, Returns, convertDartClosureToJS;
 import 'dart:_foreign_helper' show JS;
-import 'dart:_interceptors' show Interceptor, JSExtendableArray;
+import 'dart:_interceptors' show Interceptor, JSExtendableArray, JSObject;
 
 import 'dart:_metadata';
 export 'dart:_metadata';

tests/lib_2/html/postmessage_anonymous_test.dart

@@ -0,0 +1,53 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@JS()
+library postmessage_anonymous_test;
+
+import 'dart:async';
+import 'dart:html';
+import 'package:expect/expect.dart';
+import 'package:js/js.dart';
+
+const String JS_CODE = """
+window.addEventListener('message', handler);
+function handler(e) {
+  var data = e.data;
+  if (typeof data == 'string') return;
+  if (data.recipient != 'JS') return;
+  var response = {recipient: 'DART', msg: data.msg};
+  window.removeEventListener('message', handler);
+  window.postMessage(response, '*');
+}
+""";
+
+const String TEST_MSG = "hello world";
+
+@JS()
+@anonymous
+class Message {
+  external String get recipient;
+  external String get msg;
+  external factory Message({String recipient, String msg});
+}
+
+main() {
+  var subscription;
+  subscription = window.onMessage.listen((e) {
+    var data = e.data;
+    if (data is String) return;
+    if (data['recipient'] != 'DART') return;
+    subscription.cancel();
+    Expect.equals(TEST_MSG, data['msg']);
+  });
+  injectSource(JS_CODE);
+  window.postMessage(Message(recipient: 'JS', msg: TEST_MSG), '*');
+}
+
+void injectSource(String code) {
+  final script = new ScriptElement();
+  script.type = 'text/javascript';
+  script.innerHtml = code;
+  document.body.append(script);
+}