binding: Makes Dictionary throw an exception (constructor).

third_party/WebKit/Source/bindings/core/v8/Dictionary.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 31 matching lines @@
 class ExecutionContext;
 
 // Dictionary class provides ways to retrieve property values as C++ objects
 // from a V8 object. Instances of this class must not outlive V8's handle scope
 // because they hold a V8 value without putting it on persistent handles.
 class CORE_EXPORT Dictionary final {
   DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
 
  public:
   Dictionary() : m_isolate(nullptr) {}
-  Dictionary(v8::Isolate* isolate, const v8::Local<v8::Value>& options)
-      : m_options(options), m_isolate(isolate) {
-    DCHECK(m_isolate);
+  Dictionary(v8::Isolate*, v8::Local<v8::Value> dictObj, ExceptionState&);
+
+  Dictionary& operator=(const Dictionary&) = default;
+
+  bool isObject() const { return !m_dictObj.IsEmpty(); }
+  bool isUndefinedOrNull() const { return blink::isUndefinedOrNull(m_value); }
+
+  bool get(const StringView& key, Dictionary&) const;
+  bool get(const StringView& key, v8::Local<v8::Value>& value) const {
+    return getInternal(v8String(m_isolate, key), value);
   }
-  Dictionary(const v8::Local<v8::Value>& options,
-             v8::Isolate* isolate,
-             ExceptionState&)  // DEPRECATED
-      : Dictionary(isolate, options) {}
 
-  Dictionary& operator=(const Dictionary&);
-
-  bool isObject() const;
-  bool isUndefinedOrNull() const;
-
-  bool get(const StringView&, Dictionary&) const;
-  bool get(const StringView&, v8::Local<v8::Value>&) const;
-
-  v8::Local<v8::Value> v8Value() const { return m_options; }
+  v8::Local<v8::Value> v8Value() const { return m_value; }
 
   bool getOwnPropertiesAsStringHashMap(HashMap<String, String>&) const;
   bool getPropertyNames(Vector<String>&) const;
 
   bool hasProperty(const StringView&) const;
 
   v8::Isolate* isolate() const { return m_isolate; }
   v8::Local<v8::Context> v8Context() const {
     ASSERT(m_isolate);
     return m_isolate->GetCurrentContext();
   }
 
   DictionaryIterator getIterator(ExecutionContext*) const;
 
  private:
   bool getInternal(const v8::Local<v8::Value>& key,
                    v8::Local<v8::Value>& result) const;
-  bool toObject(v8::Local<v8::Object>&) const;
 
-  v8::Local<v8::Value> m_options;
   v8::Isolate* m_isolate;
+  // Undefined, Null, or Object is allowed as type of dictionary.
+  v8::Local<v8::Value> m_value;  // empty, undefined, null, or an Object
+  // In order to avoid converting a v8::Value to a v8::Object everytime, keep
+  // the converted object.
+  v8::Local<v8::Object> m_dictObj;  // an Object (same as m_value) or empty

[haraken, 2016/11/16 17:28:57]

Do we need m_dictObj? You're storing m_dictObj to m_value immediately after
converting the dictionary.

m_dictObj => m_dictionaryObject

[Yuki, 2016/11/17 07:38:53]

We need to distinguish undefined / null / an Object.  Without
m_dictionaryObject, we need to do
    m_value->IsObject()
and
    m_value.As<v8::Object>().

The advantages of having m_dictionaryObject are:
a) !m_dictionaryObject.IsEmpty() is faster than m_value->IsObject()
b) m_dictionaryObject is shorter than m_value.As<v8::Object>() and easy to read.
c) it's trivial that m_dictionaryObject is a dictionary object while m_value can
be anything.

Since we often use m_dictionaryObject as v8::Object, I'd like these advantages.

[Yuki, 2016/11/18 13:37:53]

Done.

 };
 
 template <>
 struct NativeValueTraits<Dictionary> {
-  static inline Dictionary nativeValue(v8::Isolate* isolate,
-                                       v8::Local<v8::Value> value,
-                                       ExceptionState&) {
-    return Dictionary(isolate, value);
+  static Dictionary nativeValue(v8::Isolate* isolate,
+                                v8::Local<v8::Value> value,
+                                ExceptionState& exceptionState) {
+    return Dictionary(isolate, value, exceptionState);
   }
 };
 
 // DictionaryHelper is a collection of static methods for getting or
 // converting a value from Dictionary.
 struct DictionaryHelper {
   STATIC_ONLY(DictionaryHelper);
   template <typename T>
   static bool get(const Dictionary&, const StringView& key, T& value);
   template <typename T>
@@ skipping 19 matching lines @@
   static bool get(const Dictionary&,
                   const StringView& key,
                   PointerType<T>& value);
   template <typename T>
   static bool get(const Dictionary&, const StringView& key, Nullable<T>& value);
 };
 
 }  // namespace blink
 
 #endif  // Dictionary_h