Add debug mirror support for ES6 Map/Set iterators.

src/mirror-debugger.js

 // Copyright 2006-2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Handle id counters.
 var next_handle_ = 0;
 var next_transient_handle_ = -1;
 
 // Mirror cache.
 var mirror_cache_ = [];
@@ skipping 67 matching lines @@
   } else if (IS_REGEXP(value)) {
     mirror = new RegExpMirror(value);
   } else if (IS_ERROR(value)) {
     mirror = new ErrorMirror(value);
   } else if (IS_SCRIPT(value)) {
     mirror = new ScriptMirror(value);
   } else if (IS_MAP(value) || IS_WEAKMAP(value)) {
     mirror = new MapMirror(value);
   } else if (IS_SET(value) || IS_WEAKSET(value)) {
     mirror = new SetMirror(value);
+  } else if (IS_MAP_ITERATOR(value) || IS_SET_ITERATOR(value)) {
+    mirror = new IteratorMirror(value);
   } else if (ObjectIsPromise(value)) {
     mirror = new PromiseMirror(value);
   } else if (IS_GENERATOR(value)) {
     mirror = new GeneratorMirror(value);
   } else {
     mirror = new ObjectMirror(value, OBJECT_TYPE, opt_transient);
   }
 
   if (mirror_cache_enabled_) mirror_cache_[mirror.handle()] = mirror;
   return mirror;
@@ skipping 58 matching lines @@
 var ERROR_TYPE = 'error';
 var PROPERTY_TYPE = 'property';
 var INTERNAL_PROPERTY_TYPE = 'internalProperty';
 var FRAME_TYPE = 'frame';
 var SCRIPT_TYPE = 'script';
 var CONTEXT_TYPE = 'context';
 var SCOPE_TYPE = 'scope';
 var PROMISE_TYPE = 'promise';
 var MAP_TYPE = 'map';
 var SET_TYPE = 'set';
+var ITERATOR_TYPE = 'iterator';
 var GENERATOR_TYPE = 'generator';
 
 // Maximum length when sending strings through the JSON protocol.
 var kMaxProtocolStringLength = 80;
 
 // Different kind of properties.
 var PropertyKind = {};
 PropertyKind.Named   = 1;
 PropertyKind.Indexed = 2;
 
@@ skipping 34 matching lines @@
 //       - ObjectMirror
 //         - FunctionMirror
 //           - UnresolvedFunctionMirror
 //         - ArrayMirror
 //         - DateMirror
 //         - RegExpMirror
 //         - ErrorMirror
 //         - PromiseMirror
 //         - MapMirror
 //         - SetMirror
+//         - IteratorMirror
 //         - GeneratorMirror
 //     - PropertyMirror
 //     - InternalPropertyMirror
 //     - FrameMirror
 //     - ScriptMirror
 
 
 /**
  * Base class for all mirror objects.
  * @param {string} type The type of the mirror
@@ skipping 219 matching lines @@
 /**
  * Check whether the mirror reflects a set.
  * @returns {boolean} True if the mirror reflects a set
  */
 Mirror.prototype.isSet = function() {
   return this instanceof SetMirror;
 };
 
 
 /**
+ * Check whether the mirror reflects an iterator.
+ * @returns {boolean} True if the mirror reflects an iterator
+ */
+Mirror.prototype.isIterator = function() {
+  return this instanceof IteratorMirror;
+};
+
+
+/**
  * Allocate a handle id for this object.
  */
 Mirror.prototype.allocateHandle_ = function() {
   if (mirror_cache_enabled_) this.handle_ = next_handle_++;
 };
 
 
 /**
  * Allocate a transient handle id for this object. Transient handles are
  * negative.
@@ skipping 867 matching lines @@
   return result;
 };
 
 
 function SetMirror(value) {
   %_CallFunction(this, value, SET_TYPE, ObjectMirror);
 }
 inherits(SetMirror, ObjectMirror);
 
 
+function IteratorGetValues_(iter, next_function) {
+  var result = [];
+  var next;
+  while (!(next = %_CallFunction(iter, next_function)).done) {
+    result.push(next.value);
+  }
+  return result;
+}
+
+
 /**
  * Returns an array of elements of a set.
  * This will keep elements alive for WeakSets.
  *
  * @returns {Array.<Object>} Array of elements of a set.
  */
 SetMirror.prototype.values = function() {
   if (IS_WEAKSET(this.value_)) {
     return %GetWeakSetValues(this.value_);
   }
 
-  var result = [];
   var iter = %_CallFunction(this.value_, builtins.SetValues);
-  var next;
-  while (!(next = iter.next()).done) {
-    result.push(next.value);
-  }
-  return result;
+  return IteratorGetValues_(iter, builtins.SetIteratorNextJS);
 };
 
 
+function IteratorMirror(value) {
+  %_CallFunction(this, value, ITERATOR_TYPE, ObjectMirror);
+}
+inherits(IteratorMirror, ObjectMirror);
+
+
+/**
+ * Returns a preview of elements of an iterator.
+ * Does not change the backing iterator state.
+ *
+ * @returns {Array.<Object>} Array of elements of an iterator.
+ */
+IteratorMirror.prototype.preview = function() {
+  if (IS_MAP_ITERATOR(this.value_)) {
+    return IteratorGetValues_(%MapIteratorClone(this.value_),
+                              builtins.MapIteratorNextJS);
+  } else if (IS_SET_ITERATOR(this.value_)) {
+    return IteratorGetValues_(%SetIteratorClone(this.value_),
+                              builtins.SetIteratorNextJS);
+  }
+};
+
+
 /**
  * Mirror object for a Generator object.
  * @param {Object} data The Generator object
  * @constructor
  * @extends Mirror
  */
 function GeneratorMirror(value) {
   %_CallFunction(this, value, GENERATOR_TYPE, ObjectMirror);
 }
 inherits(GeneratorMirror, ObjectMirror);
@@ skipping 1589 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }