Provide a logical view of VM-internal maps in Observatory.

runtime/vm/object_test.cc

 // Copyright (c) 2012, 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.
 
 #include "platform/globals.h"
 
 #include "vm/assembler.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
@@ skipping 4482 matching lines @@
     array.PrintJSON(&js, true);
     elideSubstring("classes", js.ToCString(), buffer);
     elideSubstring("objects", buffer, buffer);
     elideSubstring("_InternalLinkedHashMap@", buffer, buffer);
     EXPECT_STREQ(
         "{\"type\":\"@Instance\","
         "\"_vmType\":\"LinkedHashMap\","
         "\"class\":{\"type\":\"@Class\",\"fixedId\":true,\"id\":\"\","
         "\"name\":\"_InternalLinkedHashMap\",\"_vmName\":\"\"},"
         "\"kind\":\"Map\","
-        "\"id\":\"\"}",
+        "\"id\":\"\","
+        "\"length\":0}",
         buffer);
   }
   // UserTag reference
   {
     JSONStream js;
     Instance& tag = Instance::Handle(isolate->default_tag());
     tag.PrintJSON(&js, true);
     elideSubstring("classes", js.ToCString(), buffer);
     elideSubstring("objects", buffer, buffer);
     elideSubstring("_UserTag@", buffer, buffer);
@@ skipping 185 matching lines @@
 
   // 2. Create an empty internalized LinkedHashMap in C++.
   Instance& dart_map = Instance::Handle();
   dart_map ^= Api::UnwrapHandle(h_result);
   LinkedHashMap& cc_map = LinkedHashMap::Handle(LinkedHashMap::NewDefault());
 
   // 3. Expect them to have identical structure.
   CheckIdenticalHashStructure(dart_map, cc_map);
 }
 
+
+TEST_CASE(LinkedHashMap_iteration) {
+  const char* kScript =
+      "makeMap() {\n"
+      "  var map = {'x': 3, 'y': 4, 'z': 5, 'w': 6};\n"
+      "  map.remove('y');\n"
+      "  map.remove('w');\n"
+      "  return map;\n"
+      "}";
+  Dart_Handle h_lib = TestCase::LoadTestScript(kScript, NULL);
+  EXPECT_VALID(h_lib);
+  Library& lib = Library::Handle();
+  lib ^= Api::UnwrapHandle(h_lib);
+  EXPECT(!lib.IsNull());
+  Dart_Handle h_result = Dart_Invoke(h_lib, NewString("makeMap"), 0, NULL);
+  EXPECT_VALID(h_result);
+
+  Instance& dart_map = Instance::Handle();
+  dart_map ^= Api::UnwrapHandle(h_result);
+  ASSERT(dart_map.IsLinkedHashMap());
+  const LinkedHashMap& cc_map = LinkedHashMap::Cast(dart_map);
+
+  EXPECT_EQ(2, cc_map.Length());
+
+  LinkedHashMap::Iterator iterator(cc_map);
+  Object& object = Object::Handle();
+
+  EXPECT(iterator.MoveNext());
+  object = iterator.CurrentKey();
+  EXPECT_STREQ("x", object.ToCString());
+  object = iterator.CurrentValue();
+  EXPECT_STREQ("3", object.ToCString());
+
+  EXPECT(iterator.MoveNext());
+  object = iterator.CurrentKey();
+  EXPECT_STREQ("z", object.ToCString());
+  object = iterator.CurrentValue();
+  EXPECT_STREQ("5", object.ToCString());
+
+  EXPECT(!iterator.MoveNext());
+}
+
 }  // namespace dart