Maintain referential integrity of proxy instances in dart:js

sdk/lib/js/dart2js/js_dart2js.dart

Index: sdk/lib/js/dart2js/js_dart2js.dart
diff --git a/sdk/lib/js/dart2js/js_dart2js.dart b/sdk/lib/js/dart2js/js_dart2js.dart
index 64b4af0b4771972ac4ac9b773480ece956d914b8..ee42853ade7967aed247ad43af6b839816a3012d 100644
--- a/sdk/lib/js/dart2js/js_dart2js.dart
+++ b/sdk/lib/js/dart2js/js_dart2js.dart
@@ -4,7 +4,7 @@
 
 library dart.js;
 
-import 'dart:_foreign_helper' show JS;
+import 'dart:_foreign_helper' show JS, DART_CLOSURE_TO_JS;
 import 'dart:_js_helper' show Primitives, convertDartClosureToJS;
 
 final JsObject context = new JsObject._fromJs(Primitives.computeGlobalThis());
@@ -39,6 +39,34 @@ class Callback implements Serializable<JsFunction> {
   JsFunction toJs() => new JsFunction._fromJs(_jsFunction);
 }
 
+/*
+ * TODO(justinfagnani): make public when we remove Callback.
+ *
+ * Returns a [JsFunction] that captures its 'this' binding and calls [f]
+ * with the value of this passed as the first argument.
+ */
+JsFunction _captureThis(Function f) => 
+  new JsFunction._fromJs(_convertDartFunction(f, captureThis: true));
+
+_convertDartFunction(Function f, {bool captureThis: false}) {
+  return JS('',
+    'function(_call, f, captureThis) {'
+      'return function() {'
+        'return _call(f, captureThis, this, '
+            'Array.prototype.slice.apply(arguments));'
+      '}'
+    '}(#, #, #)', DART_CLOSURE_TO_JS(_callDartFunction), f, _captureThis);

[alexandre.ardhuin, 2013/10/08 08:36:44]

"captureThis" instead of "_captureThis"

[justinfagnani, 2013/10/10 23:00:07]

Done.

+}
+
+_callDartFunction(callback, bool captureThis, self, List arguments) {
+  if (captureThis) {
+    arguments = [self]..addAll(arguments);
+  }
+  var dartArgs = arguments.map(_convertToDart).toList(growable: false);
+  return _convertToJS(Function.apply(callback, dartArgs));
+}
+
+
 class JsObject implements Serializable<JsObject> {
   final dynamic _jsObject;
 
@@ -166,6 +194,14 @@ abstract class Serializable<T> {
   T toJs();
 }
 
+// property added to a Dart object referencing its JS-side DartObject proxy
+const _DART_OBJECT_PROPERTY_NAME = r'_$dart_dartObject';
+const _DART_CLOSURE_PROPERTY_NAME = r'_$dart_dartClosure';
+
+// property added to a JS object referencing its Dart-side JsObject proxy
+const _JS_OBJECT_PROPERTY_NAME = r'_$dart_jsObject';
+const _JS_FUNCTION_PROPERTY_NAME = r'$dart_jsFunction';
+
 dynamic _convertToJS(dynamic o) {
   if (o == null) {
     return null;
@@ -176,12 +212,28 @@ dynamic _convertToJS(dynamic o) {
   } else if (o is Serializable) {
     return _convertToJS(o.toJs());
   } else if (o is Function) {
-    return _convertToJS(new Callback(o));
+    var jsFunction = JS('', '#[#]', o, _JS_FUNCTION_PROPERTY_NAME);

[alexandre.ardhuin, 2013/10/08 08:36:44]

1. Use _getDartProxy ?
2. _DART_CLOSURE_PROPERTY_NAME instead of _JS_FUNCTION_PROPERTY_NAME.

[justinfagnani, 2013/10/10 23:00:07]

_getDartProxy could maybe work if we used the same property names for
referencing a dart proxy from a JS object as  for referencing a dart object from
a JS proxy. I like the separation right now. Also, this block is setting both
the JS->dart reference and the dart->JS reference. For objects we don't set the
dart->JS reference because DartObject already has it.

_JS_FUNCTION_PROPERTY_NAME is used because it's referencing the JS function
proxy from the dart closure

+    if (jsFunction == null) {
+      jsFunction = _convertDartFunction(o);
+      // set a property on the JS closure referencing the Dart closure
+      JS('void', 'Object.defineProperty(#, #, { value: #})', jsFunction,

[alexandre.ardhuin, 2013/10/08 08:36:44]

_JS_FUNCTION_PROPERTY_NAME instead of _DART_CLOSURE_PROPERTY_NAME

[justinfagnani, 2013/10/10 23:00:07]

same response/reasoning as above

+          _DART_CLOSURE_PROPERTY_NAME, o);
+      // set a property on the Dart closure referencing the JS closure
+      JS('', '#[#] = #', o, _JS_FUNCTION_PROPERTY_NAME, jsFunction);

[alexandre.ardhuin, 2013/10/08 08:36:44]

1. Use Object.defineProperty.
2. _DART_CLOSURE_PROPERTY_NAME instead of _JS_FUNCTION_PROPERTY_NAME.

[justinfagnani, 2013/10/10 23:00:07]

Done for defineProperty

+    }
+    return jsFunction;
   } else {
-    return JS('=Object', 'new DartProxy(#)', o);
+    var jsProxy = JS('', '#[#]', o, _DART_OBJECT_PROPERTY_NAME);

[alexandre.ardhuin, 2013/10/08 08:36:44]

Use _getDartProxy ?

[justinfagnani, 2013/10/10 23:00:07]

used _getJsProxy

+    if (jsProxy == null) {
+      jsProxy = JS('', 'new DartObject(#)', o);
+      JS('', '#[#] = #', o, _DART_OBJECT_PROPERTY_NAME, jsProxy);

[alexandre.ardhuin, 2013/10/08 08:36:44]

Use Object.defineProperty.

[justinfagnani, 2013/10/10 23:00:07]

Done.

+    }
+    return jsProxy;
   }
 }
 
+// converts a Dart object to a reference to a native JS object
+// which might be a DartObject JS->Dart proxy
 dynamic _convertToDart(dynamic o) {
   if (JS('bool', '# == null', o)) {
     return null;
@@ -190,10 +242,22 @@ dynamic _convertToDart(dynamic o) {
       JS('bool', 'typeof # == "boolean" || # instanceof Boolean', o, o)) {
     return o;
   } else if (JS('bool', '# instanceof Function', o)) {
-    return new JsFunction._fromJs(JS('=Object', '#', o));
-  } else if (JS('bool', '# instanceof DartProxy', o)) {
+    return _getDartProxy(o, _JS_FUNCTION_PROPERTY_NAME,
+        (o) => new JsFunction._fromJs(o));
+  } else if (JS('bool', '# instanceof DartObject', o)) {
     return JS('var', '#.o', o);
   } else {
-    return new JsObject._fromJs(JS('=Object', '#', o));
+    return _getDartProxy(o, _JS_OBJECT_PROPERTY_NAME,
+        (o) => new JsObject._fromJs(o));
   }
-}
+}
+
+dynamic _getDartProxy(o, String propertyName, createProxy(o)) {
+  var dartProxy = JS('', '#[#]', o, propertyName);
+  if (dartProxy == null) {
+    dartProxy = createProxy(JS('=Object', '#', o));
+    JS('void', 'Object.defineProperty(#, #, { value: #})', o, propertyName,
+        dartProxy);
+  }
+  return dartProxy;
+}