Treat null like the object it is in the Observatory and Service.

runtime/vm/object_id_ring_test.cc

Index: runtime/vm/object_id_ring_test.cc
diff --git a/runtime/vm/object_id_ring_test.cc b/runtime/vm/object_id_ring_test.cc
index aeae8e233296ac67ddb2d1528c96f70f0d1015b4..e22bb9078bbb9ffc73ebf54d3d803e63c966fd13 100644
--- a/runtime/vm/object_id_ring_test.cc
+++ b/runtime/vm/object_id_ring_test.cc
@@ -45,12 +45,13 @@ TEST_CASE(ObjectIdRingSerialWrapTest) {
   ObjectIdRing* ring = isolate->object_id_ring();
   ObjectIdRingTestHelper::SetCapacityAndMaxSerial(ring, 2, 4);
   intptr_t id;
+  ObjectIdRing::LookupResult kind;
   id = ring->GetIdForObject(ObjectIdRingTestHelper::MakeString("0"));
   EXPECT_EQ(0, id);
   id = ring->GetIdForObject(ObjectIdRingTestHelper::MakeString("1"));
   EXPECT_EQ(1, id);
   // Test that id 1 gives us the "1" string.
-  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id), "1");
+  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id, &kind), "1");

[turnidge, 2014/08/27 16:13:56]

Can you add checks that kind is the right value?

EXPECT_EQ(kWhatever, kind);

It would also be good to have at least one test which returns kInvalid,
kExpired, and kCollected.

Instead of forcing an object to be *really* gc'ed, you could add a test-only
function on the id ring which fakes an object being collected.

[rmacnak, 2014/08/27 18:09:59]

Added
One of the existing test already checks the GC'd case, so only added one for the
expired case. (kInvalid happens in service.cc)

   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 0);
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 1);
   ObjectIdRingTestHelper::ExpectIdIsInvalid(ring, 2);
@@ -69,14 +70,14 @@ TEST_CASE(ObjectIdRingSerialWrapTest) {
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 3);
   id = ring->GetIdForObject(ObjectIdRingTestHelper::MakeString("4"));
   EXPECT_EQ(0, id);
-  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id), "4");
+  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id, &kind), "4");
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 0);
   ObjectIdRingTestHelper::ExpectIdIsInvalid(ring, 1);
   ObjectIdRingTestHelper::ExpectIdIsInvalid(ring, 2);
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 3);
   id = ring->GetIdForObject(ObjectIdRingTestHelper::MakeString("5"));
   EXPECT_EQ(1, id);
-  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id), "5");
+  ObjectIdRingTestHelper::ExpectString(ring->GetObjectForId(id, &kind), "5");
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 0);
   ObjectIdRingTestHelper::ExpectIdIsValid(ring, 1);
   ObjectIdRingTestHelper::ExpectIdIsInvalid(ring, 2);
@@ -101,6 +102,7 @@ TEST_CASE(ObjectIdRingScavengeMoveTest) {
   Isolate* isolate = Isolate::Current();
   Heap* heap = isolate->heap();
   ObjectIdRing* ring = isolate->object_id_ring();
+  ObjectIdRing::LookupResult kind;
   RawObject* raw_obj = Api::UnwrapHandle(result);
   // Located in new heap.
   EXPECT(raw_obj->IsNewObject());
@@ -110,9 +112,9 @@ TEST_CASE(ObjectIdRingScavengeMoveTest) {
   intptr_t raw_obj_id2 = ring->GetIdForObject(raw_obj);
   EXPECT_EQ(1, raw_obj_id2);
   intptr_t raw_obj_id3 = ring->GetIdForObject(Object::null());
-  RawObject* raw_obj1 = ring->GetObjectForId(raw_obj_id1);
-  RawObject* raw_obj2 = ring->GetObjectForId(raw_obj_id2);
-  RawObject* raw_obj3 = ring->GetObjectForId(raw_obj_id3);
+  RawObject* raw_obj1 = ring->GetObjectForId(raw_obj_id1, &kind);
+  RawObject* raw_obj2 = ring->GetObjectForId(raw_obj_id2, &kind);
+  RawObject* raw_obj3 = ring->GetObjectForId(raw_obj_id3, &kind);
   EXPECT_NE(Object::null(), raw_obj1);
   EXPECT_NE(Object::null(), raw_obj2);
   EXPECT_EQ(Object::null(), raw_obj3);
@@ -120,9 +122,9 @@ TEST_CASE(ObjectIdRingScavengeMoveTest) {
   EXPECT_EQ(RawObject::ToAddr(raw_obj), RawObject::ToAddr(raw_obj2));
   // Force a scavenge.
   heap->CollectGarbage(Heap::kNew);
-  RawObject* raw_object_moved1 = ring->GetObjectForId(raw_obj_id1);
-  RawObject* raw_object_moved2 = ring->GetObjectForId(raw_obj_id2);
-  RawObject* raw_object_moved3 = ring->GetObjectForId(raw_obj_id3);
+  RawObject* raw_object_moved1 = ring->GetObjectForId(raw_obj_id1, &kind);
+  RawObject* raw_object_moved2 = ring->GetObjectForId(raw_obj_id2, &kind);
+  RawObject* raw_object_moved3 = ring->GetObjectForId(raw_obj_id3, &kind);
   EXPECT_NE(Object::null(), raw_object_moved1);
   EXPECT_NE(Object::null(), raw_object_moved2);
   EXPECT_EQ(Object::null(), raw_object_moved3);
@@ -147,6 +149,7 @@ TEST_CASE(ObjectIdRingOldGCTest) {
   Heap* heap = isolate->heap();
   ObjectIdRing* ring = isolate->object_id_ring();
 
+  ObjectIdRing::LookupResult kind;
   intptr_t raw_obj_id1 = -1;
   intptr_t raw_obj_id2 = -1;
   {
@@ -169,8 +172,8 @@ TEST_CASE(ObjectIdRingOldGCTest) {
     EXPECT_EQ(0, raw_obj_id1);
     raw_obj_id2 = ring->GetIdForObject(raw_obj);
     EXPECT_EQ(1, raw_obj_id2);
-    RawObject* raw_obj1 = ring->GetObjectForId(raw_obj_id1);
-    RawObject* raw_obj2 = ring->GetObjectForId(raw_obj_id2);
+    RawObject* raw_obj1 = ring->GetObjectForId(raw_obj_id1, &kind);
+    RawObject* raw_obj2 = ring->GetObjectForId(raw_obj_id2, &kind);
     EXPECT_NE(Object::null(), raw_obj1);
     EXPECT_NE(Object::null(), raw_obj2);
     EXPECT_EQ(RawObject::ToAddr(raw_obj), RawObject::ToAddr(raw_obj1));
@@ -182,8 +185,8 @@ TEST_CASE(ObjectIdRingOldGCTest) {
   // collected and the object id ring will now return the null object for
   // those ids.
   heap->CollectGarbage(Heap::kOld);
-  RawObject* raw_object_moved1 = ring->GetObjectForId(raw_obj_id1);
-  RawObject* raw_object_moved2 = ring->GetObjectForId(raw_obj_id2);
+  RawObject* raw_object_moved1 = ring->GetObjectForId(raw_obj_id1, &kind);
+  RawObject* raw_object_moved2 = ring->GetObjectForId(raw_obj_id2, &kind);
   // Objects should now be null.
   EXPECT_EQ(Object::null(), raw_object_moved1);
   EXPECT_EQ(Object::null(), raw_object_moved2);