Add scope chain information to the debugger

src/mirror-delay.js

Index: src/mirror-delay.js
===================================================================
--- src/mirror-delay.js	(revision 2147)
+++ src/mirror-delay.js	(working copy)
@@ -34,9 +34,14 @@
 Date;
 
 
+// Handle id counters.
 var next_handle_ = 0;
+var next_transient_handle_ = -1;
+
+// Mirror cache.
 var mirror_cache_ = [];
 
+
 /**
  * Clear the mirror handle cache.
  */
@@ -50,20 +55,26 @@
  * Returns the mirror for a specified value or object.
  *
  * @param {value or Object} value the value or object to retreive the mirror for
+ * @param {boolean} transient indicate whether this object is transient and
+ *    should not be added to the mirror cache. The default is not transient.
  * @returns {Mirror} the mirror reflects the passed value or object
  */
-function MakeMirror(value) {
+function MakeMirror(value, opt_transient) {
   var mirror;
-  for (id in mirror_cache_) {
-    mirror = mirror_cache_[id];
-    if (mirror.value() === value) {
-      return mirror;
+
+  // Look for non transient mirrors in the mirror cache.
+  if (!opt_transient) {
+    for (id in mirror_cache_) {
+      mirror = mirror_cache_[id];
+      if (mirror.value() === value) {
+        return mirror;
+      }
+      // Special check for NaN as NaN == NaN is false.
+      if (mirror.isNumber() && isNaN(mirror.value()) &&
+          typeof value == 'number' && isNaN(value)) {
+        return mirror;
+      }
     }
-    // Special check for NaN as NaN == NaN is false.
-    if (mirror.isNumber() && isNaN(mirror.value()) &&
-        typeof value == 'number' && isNaN(value)) {
-      return mirror;
-    }
   }
   
   if (IS_UNDEFINED(value)) {
@@ -89,7 +100,7 @@
   } else if (IS_SCRIPT(value)) {
     mirror = new ScriptMirror(value);
   } else {
-    mirror = new ObjectMirror(value);
+    mirror = new ObjectMirror(value, OBJECT_TYPE, opt_transient);
   }
 
   mirror_cache_[mirror.handle()] = mirror;
@@ -155,6 +166,7 @@
 const FRAME_TYPE = 'frame';
 const SCRIPT_TYPE = 'script';
 const CONTEXT_TYPE = 'context';
+const SCOPE_TYPE = 'scope';
 
 // Maximum length when sending strings through the JSON protocol.
 const kMaxProtocolStringLength = 80;
@@ -185,6 +197,13 @@
 PropertyAttribute.DontDelete = DONT_DELETE;
 
 
+// A copy of the scope types from runtime.cc.
+ScopeType = { Global: 0,
+              Local: 1,
+              With: 2,
+              Closure: 3 };
+
+
 // Mirror hierarchy:
 //   - Mirror
 //     - ValueMirror
@@ -373,6 +392,15 @@
 
 
 /**
+ * Check whether the mirror reflects a scope.
+ * @returns {boolean} True if the mirror reflects a scope
+ */
+Mirror.prototype.isScope = function() {
+  return this instanceof ScopeMirror;
+}
+
+
+/**
  * Allocate a handle id for this object.
  */
 Mirror.prototype.allocateHandle_ = function() {
@@ -380,6 +408,15 @@
 }
 
 
+/**
+ * Allocate a transient handle id for this object. Transient handles are
+ * negative.
+ */
+Mirror.prototype.allocateTransientHandle_ = function() {
+  this.handle_ = next_transient_handle_--;
+}
+
+
 Mirror.prototype.toText = function() {
   // Simpel to text which is used when on specialization in subclass.
   return "#<" + builtins.GetInstanceName(this.constructor.name) + ">";
@@ -390,13 +427,19 @@
  * Base class for all value mirror objects.
  * @param {string} type The type of the mirror
  * @param {value} value The value reflected by this mirror
+ * @param {boolean} transient indicate whether this object is transient with a
+ *    transient handle
  * @constructor
  * @extends Mirror
  */
-function ValueMirror(type, value) {
+function ValueMirror(type, value, transient) {
   Mirror.call(this, type);
   this.value_ = value;
-  this.allocateHandle_();
+  if (!transient) {
+    this.allocateHandle_();
+  } else {
+    this.allocateTransientHandle_();
+  }
 }
 inherits(ValueMirror, Mirror);
 
@@ -525,11 +568,13 @@
 /**
  * Mirror object for objects.
  * @param {object} value The object reflected by this mirror
+ * @param {boolean} transient indicate whether this object is transient with a
+ *    transient handle
  * @constructor
  * @extends ValueMirror
  */
-function ObjectMirror(value, type) {
-  ValueMirror.call(this, type || OBJECT_TYPE, value);
+function ObjectMirror(value, type, transient) {
+  ValueMirror.call(this, type || OBJECT_TYPE, value, transient);
 }
 inherits(ObjectMirror, ValueMirror);
 
@@ -1080,7 +1125,7 @@
 
 
 PropertyMirror.prototype.value = function() {
-  return MakeMirror(this.value_);
+  return MakeMirror(this.value_, false);
 }
 
 
@@ -1135,7 +1180,7 @@
   if (this.hasGetter()) {
     return MakeMirror(this.getter_);
   } else {
-    return new UndefinedMirror();
+    return GetUndefinedMirror();
   }
 }
 
@@ -1149,7 +1194,7 @@
   if (this.hasSetter()) {
     return MakeMirror(this.setter_);
   } else {
-    return new UndefinedMirror();
+    return GetUndefinedMirror();
   }
 }
 
@@ -1294,6 +1339,11 @@
 }
 
 
+FrameDetails.prototype.scopeCount = function() {
+  return %GetScopeCount(this.break_id_, this.frameId());
+}
+
+
 /**
  * Mirror object for stack frames.
  * @param {number} break_id The break id in the VM for which this frame is
@@ -1419,6 +1469,16 @@
 };
 
 
+FrameMirror.prototype.scopeCount = function() {
+  return this.details_.scopeCount();
+};
+
+
+FrameMirror.prototype.scope = function(index) {
+  return new ScopeMirror(this, index);
+};
+
+
 FrameMirror.prototype.evaluate = function(source, disable_break) {
   var result = %DebugEvaluate(this.break_id_, this.details_.frameId(),
                               source, Boolean(disable_break));
@@ -1562,7 +1622,71 @@
 }
 
 
+const kScopeDetailsTypeIndex = 0;
+const kScopeDetailsObjectIndex = 1;
+
+function ScopeDetails(frame, index) {
+  this.break_id_ = frame.break_id_;
+  this.details_ = %GetScopeDetails(frame.break_id_,
+                                   frame.details_.frameId(),
+                                   index);
+}
+
+
+ScopeDetails.prototype.type = function() {
+  %CheckExecutionState(this.break_id_);
+  return this.details_[kScopeDetailsTypeIndex];
+}
+
+
+ScopeDetails.prototype.object = function() {
+  %CheckExecutionState(this.break_id_);
+  return this.details_[kScopeDetailsObjectIndex];
+}
+
+
 /**
+ * Mirror object for scope.
+ * @param {FrameMirror} frame The frame this scope is a part of
+ * @param {number} index The scope index in the frame
+ * @constructor
+ * @extends Mirror
+ */
+function ScopeMirror(frame, index) {
+  Mirror.call(this, SCOPE_TYPE);
+  this.frame_index_ = frame.index_;
+  this.scope_index_ = index;
+  this.details_ = new ScopeDetails(frame, index);
+}
+inherits(ScopeMirror, Mirror);
+
+
+ScopeMirror.prototype.frameIndex = function() {
+  return this.frame_index_;
+};
+
+
+ScopeMirror.prototype.scopeIndex = function() {
+  return this.scope_index_;
+};
+
+
+ScopeMirror.prototype.scopeType = function() {
+  return this.details_.type();
+};
+
+
+ScopeMirror.prototype.scopeObject = function() {
+  // For local and closure scopes create a transient mirror as these objects are
+  // created on the fly materializing the local or closure scopes and
+  // therefore will not preserve identity.
+  var transient = this.scopeType() == ScopeType.Local ||
+                  this.scopeType() == ScopeType.Closure;
+  return MakeMirror(this.details_.object(), transient);
+};
+
+
+/**
  * Mirror object for script source.
  * @param {Script} script The script object
  * @constructor
@@ -1829,6 +1953,7 @@
   return o;
 };
 
+
 JSONProtocolSerializer.prototype.serialize_ = function(mirror, reference,
                                                        details) {
   // If serializing a reference to a mirror just return the reference and add
@@ -1900,6 +2025,11 @@
       this.serializeFrame_(mirror, content);
       break;
 
+    case SCOPE_TYPE:
+      // Add object representation.
+      this.serializeScope_(mirror, content);
+      break;
+
     case SCRIPT_TYPE:
       // Script is represented by id, name and source attributes.
       if (mirror.name()) {
@@ -2102,6 +2232,14 @@
 }
 
 
+JSONProtocolSerializer.prototype.serializeScope_ = function(mirror, content) {
+  content.index = mirror.scopeIndex();
+  content.frameIndex = mirror.frameIndex();
+  content.type = mirror.scopeType();
+  content.object = this.serializeReference(mirror.scopeObject());
+}
+
+
 /**
  * Convert a number to a protocol value. For all finite numbers the number
  * itself is returned. For non finite numbers NaN, Infinite and