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

runtime/vm/service.cc

 // Copyright (c) 2013, 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 "vm/service.h"
 
 #include "include/dart_api.h"
 #include "platform/globals.h"
 
 #include "vm/compiler.h"
@@ skipping 936 matching lines @@
   return true;
 }
 
 
 static bool ContainsNonInstance(const Object& obj) {
   if (obj.IsArray()) {
     const Array& array = Array::Cast(obj);
     Object& element = Object::Handle();
     for (intptr_t i = 0; i < array.Length(); ++i) {
       element = array.At(i);
-      if (!element.IsInstance()) {
+      if (!(element.IsInstance() || element.IsNull())) {
         return true;
       }
     }
     return false;
   } else if (obj.IsGrowableObjectArray()) {
     const GrowableObjectArray& array = GrowableObjectArray::Cast(obj);
     Object& element = Object::Handle();
     for (intptr_t i = 0; i < array.Length(); ++i) {
       element = array.At(i);
-      if (!element.IsInstance()) {
+      if (!(element.IsInstance() || element.IsNull())) {
         return true;
       }
     }
     return false;
   } else {
-    return !obj.IsInstance();
+    return !(obj.IsInstance() || obj.IsNull());
   }
 }
 
 
 static bool HandleInboundReferences(Isolate* isolate,
                                     Object* target,
                                     intptr_t limit,
                                     JSONStream* js) {
   ObjectGraph graph(isolate);
   Array& path = Array::Handle(Array::New(limit * 2));
@@ skipping 89 matching lines @@
   // We nil out the array after generating the response to prevent
   // reporting suprious references when looking for inbound references
   // after looking for a retaining path.
   for (intptr_t i = 0; i < limit; ++i) {
     path.SetAt(i * 2, Object::null_object());
   }
 
   return true;
 }
 
+
 // Takes an Object* only because RetainingPath temporarily clears it.
 static bool HandleInstanceCommands(Isolate* isolate,
                                    Object* obj,
+                                   ObjectIdRing::LookupResult kind,
                                    JSONStream* js,
                                    intptr_t arg_pos) {
   ASSERT(js->num_arguments() > arg_pos);
+  ASSERT(kind != ObjectIdRing::kInvalid);
   const char* action = js->GetArgument(arg_pos);
   if (strcmp(action, "eval") == 0) {
     if (js->num_arguments() > (arg_pos + 1)) {
       PrintError(js, "expected at most %" Pd " arguments but found %" Pd "\n",
                  arg_pos + 1,
                  js->num_arguments());
       return true;
     }
-    if (obj->IsNull()) {
+    if (kind == ObjectIdRing::kCollected) {
       PrintErrorWithKind(js, "EvalCollected",
                          "attempt to evaluate against collected object\n",
                          js->num_arguments());
       return true;
     }
-    if (obj->raw() == Object::sentinel().raw()) {
+    if (kind == ObjectIdRing::kExpired) {
       PrintErrorWithKind(js, "EvalExpired",
                          "attempt to evaluate against expired object\n",
                          js->num_arguments());
       return true;
     }
     if (ContainsNonInstance(*obj)) {
       PrintError(js, "attempt to evaluate against internal VM object\n");
       return true;
     }
     const char* expr = js->LookupOption("expr");
     if (expr == NULL) {
       PrintError(js, "eval expects an 'expr' option\n",
                  js->num_arguments());
       return true;
     }
     const String& expr_str = String::Handle(isolate, String::New(expr));
     ASSERT(obj->IsInstance());
     const Instance& instance = Instance::Cast(*obj);
     const Object& result =
         Object::Handle(instance.Evaluate(expr_str,
                                          Array::empty_array(),
                                          Array::empty_array()));
     result.PrintJSON(js, true);
     return true;
   } else if (strcmp(action, "retained") == 0) {
+    if (kind == ObjectIdRing::kCollected) {
+      PrintErrorWithKind(
+          js, "RetainedCollected",
+          "attempt to calculate size retained by a collected object\n",
+          js->num_arguments());
+      return true;
+    }
+    if (kind == ObjectIdRing::kExpired) {
+      PrintErrorWithKind(
+          js, "RetainedExpired",
+          "attempt to calculate size retained by an expired object\n",
+          js->num_arguments());
+      return true;
+    }
     ObjectGraph graph(isolate);
     intptr_t retained_size = graph.SizeRetainedByInstance(*obj);
     const Object& result = Object::Handle(Integer::New(retained_size));
     result.PrintJSON(js, true);
     return true;
   } else if (strcmp(action, "retaining_path") == 0) {
+    if (kind == ObjectIdRing::kCollected) {
+      PrintErrorWithKind(
+          js, "RetainingPathCollected",
+          "attempt to find a retaining path for a collected object\n",
+          js->num_arguments());
+      return true;
+    }
+    if (kind == ObjectIdRing::kExpired) {
+      PrintErrorWithKind(
+          js, "RetainingPathExpired",
+          "attempt to find a retaining path for an expired object\n",
+          js->num_arguments());
+      return true;
+    }
     intptr_t limit;
     if (!GetIntegerId(js->LookupOption("limit"), &limit)) {
       PrintError(js, "retaining_path expects a 'limit' option\n",
                  js->num_arguments());
       return true;
     }
     return HandleRetainingPath(isolate, obj, limit, js);
   } else if (strcmp(action, "inbound_references") == 0) {
+    if (kind == ObjectIdRing::kCollected) {
+      PrintErrorWithKind(
+          js, "InboundReferencesCollected",
+          "attempt to find inbound references for a collected object\n",
+          js->num_arguments());
+      return true;
+    }
+    if (kind == ObjectIdRing::kExpired) {
+      PrintErrorWithKind(
+          js, "InboundReferencesExpired",
+          "attempt to find inbound references for an expired object\n",
+          js->num_arguments());
+      return true;
+    }
     intptr_t limit;
     if (!GetIntegerId(js->LookupOption("limit"), &limit)) {
       PrintError(js, "inbound_references expects a 'limit' option\n",
                  js->num_arguments());
       return true;
     }
     return HandleInboundReferences(isolate, obj, limit, js);
   }
 
   PrintError(js, "unrecognized action '%s'\n", action);
@@ skipping 175 matching lines @@
   Type& type = Type::Handle();
   type ^= cls.CanonicalTypeFromIndex(id);
   if (type.IsNull()) {
     PrintError(js, "Canonical type %" Pd " not found", id);
     return true;
   }
   if (js->num_arguments() == 4) {
     type.PrintJSON(js, false);
     return true;
   }
-  return HandleInstanceCommands(isolate, &type, js, 4);
+  return HandleInstanceCommands(isolate, &type, ObjectIdRing::kValid, js, 4);
 }
 
 
 static bool HandleClassesRetained(Isolate* isolate, const Class& cls,
                                   JSONStream* js) {
   if (js->num_arguments() != 3) {
     PrintError(js, "Command too long");
     return true;
   }
   ObjectGraph graph(isolate);
@@ skipping 283 matching lines @@
                             const char* preview) {
   JSONObject jsobj(js);
   jsobj.AddProperty("type", "Null");
   jsobj.AddProperty("id", id);
   jsobj.AddProperty("valueAsString", preview);
 }
 
 
 static RawObject* LookupObjectId(Isolate* isolate,
                                  const char* arg,
-                                 bool* error) {
-  *error = false;
+                                 ObjectIdRing::LookupResult* kind) {
+  *kind = ObjectIdRing::kValid;
   if (strncmp(arg, "int-", 4) == 0) {
     arg += 4;
     int64_t value = 0;
     if (!OS::StringToInt64(arg, &value) ||
         !Smi::IsValid(value)) {
-      *error = true;
+      *kind = ObjectIdRing::kInvalid;
       return Object::null();
     }
     const Integer& obj =
         Integer::Handle(isolate, Smi::New(static_cast<intptr_t>(value)));
     return obj.raw();
-
   } else if (strcmp(arg, "bool-true") == 0) {
     return Bool::True().raw();
-
   } else if (strcmp(arg, "bool-false") == 0) {
     return Bool::False().raw();
+  } else if (strcmp(arg, "null") == 0) {
+    return Object::null();
+  } else if (strcmp(arg, "not-initialized") == 0) {
+    return Object::sentinel().raw();
+  } else if (strcmp(arg, "being-initialized") == 0) {
+    return Object::transition_sentinel().raw();
   }
 
   ObjectIdRing* ring = isolate->object_id_ring();
   ASSERT(ring != NULL);
   intptr_t id = -1;
   if (!GetIntegerId(arg, &id)) {
-    *error = true;
-    return Instance::null();
+    *kind = ObjectIdRing::kInvalid;
+    return Object::null();
   }
-  return ring->GetObjectForId(id);
+  return ring->GetObjectForId(id, kind);
 }
 
 
 static RawClass* GetMetricsClass(Isolate* isolate) {
   const Library& prof_lib =
       Library::Handle(isolate, Library::ProfilerLibrary());
   ASSERT(!prof_lib.IsNull());
   const String& metrics_cls_name =
       String::Handle(isolate, String::New("Metrics"));
   ASSERT(!metrics_cls_name.IsNull());
@@ skipping 112 matching lines @@
 
 static bool HandleObjects(Isolate* isolate, JSONStream* js) {
   REQUIRE_COLLECTION_ID("objects");
   if (js->num_arguments() < 2) {
     PrintError(js, "expected at least 2 arguments but found %" Pd "\n",
                js->num_arguments());
     return true;
   }
   const char* arg = js->GetArgument(1);
 
-  // Handle special objects first.
-  if (strcmp(arg, "null") == 0) {
+  // Handle special non-objects first.
+  if (strcmp(arg, "optimized-out") == 0) {
     if (js->num_arguments() > 2) {
       PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
                  js->num_arguments());
-    } else {
-      Instance::null_instance().PrintJSON(js, false);
-    }
-    return true;
-
-  } else if (strcmp(arg, "not-initialized") == 0) {
-    if (js->num_arguments() > 2) {
-      PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
-                 js->num_arguments());
-    } else {
-      Object::sentinel().PrintJSON(js, false);
-    }
-    return true;
-
-  } else if (strcmp(arg, "being-initialized") == 0) {
-    if (js->num_arguments() > 2) {
-      PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
-                 js->num_arguments());
-    } else {
-      Object::transition_sentinel().PrintJSON(js, false);
-    }
-    return true;
-
-  } else if (strcmp(arg, "optimized-out") == 0) {
-    if (js->num_arguments() > 2) {
-      PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
-                 js->num_arguments());
     } else {
       Symbols::OptimizedOut().PrintJSON(js, false);
     }
     return true;
 
   } else if (strcmp(arg, "collected") == 0) {
     if (js->num_arguments() > 2) {
       PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
                  js->num_arguments());
     } else {
       PrintPseudoNull(js, "objects/collected", "<collected>");
     }
     return true;
 
   } else if (strcmp(arg, "expired") == 0) {
     if (js->num_arguments() > 2) {
       PrintError(js, "expected at most 2 arguments but found %" Pd "\n",
                  js->num_arguments());
     } else {
       PrintPseudoNull(js, "objects/expired", "<expired>");
     }
     return true;
   }
 
   // Lookup the object.
   Object& obj = Object::Handle(isolate);
-  bool error = false;
-  obj = LookupObjectId(isolate, arg, &error);
-  if (error) {
+  ObjectIdRing::LookupResult kind = ObjectIdRing::kInvalid;
+  obj = LookupObjectId(isolate, arg, &kind);
+  if (kind == ObjectIdRing::kInvalid) {
     PrintError(js, "unrecognized object id '%s'", arg);
     return true;
   }
   if (js->num_arguments() == 2) {
     // Print.
-    if (obj.IsNull()) {
+    if (kind == ObjectIdRing::kCollected) {
       // The object has been collected by the gc.
       PrintPseudoNull(js, "objects/collected", "<collected>");
       return true;
-    } else if (obj.raw() == Object::sentinel().raw()) {
+    } else if (kind == ObjectIdRing::kExpired) {
       // The object id has expired.
       PrintPseudoNull(js, "objects/expired", "<expired>");
       return true;
     }
     obj.PrintJSON(js, false);
     return true;
   }
-  return HandleInstanceCommands(isolate, &obj, js, 2);
+  return HandleInstanceCommands(isolate, &obj, kind, js, 2);
 }
 
 
 static bool HandleScriptsEnumerate(Isolate* isolate, JSONStream* js) {
   JSONObject jsobj(js);
   jsobj.AddProperty("type", "ScriptList");
   jsobj.AddProperty("id", "scripts");
   JSONArray members(&jsobj, "members");
   const GrowableObjectArray& libs =
       GrowableObjectArray::Handle(isolate->object_store()->libraries());
@@ skipping 795 matching lines @@
   while (current != NULL) {
     if (strcmp(name, current->name()) == 0) {
       return current;
     }
     current = current->next();
   }
   return NULL;
 }
 
 }  // namespace dart