Make Object.observe on the global object functional

test/cctest/test-object-observe.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 200 matching lines @@
         "for (var i = 0; i < 100; ++i) {"
         "  objArr.push({});"
         "  Object.observe(objArr[objArr.length-1], function(){});"
         "}"
         "Object.observe(obj, observer);");
   }
   // obj is now marked "is_observed", but our map has moved.
   CompileRun("obj.foo = 'bar'");
   CHECK(CompileRun("ran")->BooleanValue());
 }
+
+TEST(GlobalObjectObservation) {
+  HarmonyIsolate isolate;
+  HandleScope scope;
+  LocalContext context;
+  Handle<Object> global_proxy = context->Global();
+  Handle<Object> inner_global = global_proxy->GetPrototype().As<Object>();
+  CompileRun(
+      "var records = [];"
+      "var global = this;"
+      "Object.observe(global, function(r) { [].push.apply(records, r) });"
+      "global.foo = 'hello';");
+  CHECK_EQ(1, CompileRun("records.length")->Int32Value());
+  CHECK(global_proxy->StrictEquals(CompileRun("records[0].object")));
+
+  // Detached, mutating the proxy has no effect.
+  context->DetachGlobal();
+  CompileRun("global.bar = 'goodbye';");
+  CHECK_EQ(1, CompileRun("records.length")->Int32Value());
+
+  // Mutating the global object directly still has an effect...
+  CompileRun("this.bar = 'goodbye';");
+  CHECK_EQ(2, CompileRun("records.length")->Int32Value());
+  CHECK(inner_global->StrictEquals(CompileRun("records[1].object")));

[abarth-chromium, 2012/11/26 22:53:08]

So, records[1].object no longer points to the global_proxy?  I guess that makes
sense.

+
+  // Reattached, back to global proxy.
+  context->ReattachGlobal(global_proxy);
+  CompileRun("global.baz = 'again';");
+  CHECK_EQ(3, CompileRun("records.length")->Int32Value());
+  CHECK(global_proxy->StrictEquals(CompileRun("records[2].object")));

[abarth-chromium, 2012/11/26 22:53:08]

What would happen if you grabbed a reference to records[1].object on line 245? 
Would it be strictly equal to global_proxy or inner_global at this point?

+
+  // Attached to a different context, should not leak mutations
+  // to the old context.
+  context->DetachGlobal();
+  {
+    LocalContext context2;
+    context2->DetachGlobal();
+    context2->ReattachGlobal(global_proxy);

[rossberg, 2012/12/03 13:26:18]

Is this equivalent to calling Context::New with a given global object? (That's
what the WebKit bindings do, I believe.)

[adamk, 2012/12/03 19:23:20]

Added an explicit test for that codepath as it's a bit different.

+    CompileRun(
+      "var records2 = [];"
+      "Object.observe(this, function(r) { [].push.apply(records2, r) });"
+      "this.bat = 'context2';");
+    CHECK_EQ(1, CompileRun("records2.length")->Int32Value());
+    CHECK(global_proxy->StrictEquals(CompileRun("records2[0].object")));
+  }
+  CHECK_EQ(3, CompileRun("records.length")->Int32Value());
+}