gin: Use V8 Maybe APIs

gin/converter.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GIN_CONVERTER_H_
 #define GIN_CONVERTER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/strings/string_piece.h"
 #include "gin/gin_export.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 
+template<typename KeyType>
+bool SetProperty(v8::Isolate* isolate,
+                 v8::Local<v8::Object> object,
+                 KeyType key,
+                 v8::Local<v8::Value> value) {
+  auto maybe = object->Set(isolate->GetCurrentContext(), key, value);
+  return !maybe.IsNothing() && maybe.FromJust();
+}
+
 template<typename T, typename Enable = void>
 struct Converter {};
 
 template<>
 struct GIN_EXPORT Converter<bool> {
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
                                     bool val);
   static bool FromV8(v8::Isolate* isolate,
                      v8::Handle<v8::Value> val,
                      bool* out);
@@ skipping 111 matching lines @@
 struct GIN_EXPORT Converter<v8::Handle<v8::Value> > {
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
                                     v8::Handle<v8::Value> val);
   static bool FromV8(v8::Isolate* isolate,
                      v8::Handle<v8::Value> val,
                      v8::Handle<v8::Value>* out);
 };
 
 template<typename T>
 struct Converter<std::vector<T> > {
+  // If this function fails to set an element due to an exception, this returns
+  // an empty handle.
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
                                     const std::vector<T>& val) {
     v8::Handle<v8::Array> result(
         v8::Array::New(isolate, static_cast<int>(val.size())));
     for (size_t i = 0; i < val.size(); ++i) {
-      result->Set(static_cast<int>(i), Converter<T>::ToV8(isolate, val[i]));
+      if (!SetProperty(isolate, result, static_cast<int>(i),
+                       Converter<T>::ToV8(isolate, val[i])))
+        return v8::Handle<v8::Value>();

[jochen (gone - plz use gerrit), 2015/04/28 11:14:20]

we shouldn't return empty handles but MaybeLocal<> values

[bashi, 2015/05/01 03:50:35]

Changing return type requires 3-way CLs.
1. Add Maybe version of Converter::ToV8()
2. Use them in other components which depend on gin
3. Remove the current ToV8()

Does this sound reasonable? Then I'll do that.

Also, should we change all Converter::ToV8() to return MaybeLocal for
consistency?

     }
     return result;
   }
 
   static bool FromV8(v8::Isolate* isolate,
                      v8::Handle<v8::Value> val,
                      std::vector<T>* out) {
     if (!val->IsArray())
       return false;
 
@@ skipping 36 matching lines @@
 bool ConvertFromV8(v8::Isolate* isolate, v8::Handle<v8::Value> input,
                    T* result) {
   return Converter<T>::FromV8(isolate, input, result);
 }
 
 GIN_EXPORT std::string V8ToString(v8::Handle<v8::Value> value);
 
 }  // namespace gin
 
 #endif  // GIN_CONVERTER_H_