Check whether key exists in Dictionary::Get

native_mate/converter.h

@@ -15,6 +15,20 @@
 
 namespace mate {
 
+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>
+struct ToV8ReturnsMaybe {
+  static const bool value = false;
+};
+
 template<typename T, typename Enable = void>
 struct Converter {};
 
@@ -241,10 +255,14 @@ struct Converter<std::set<T> > {
   }
 };
 
+template<typename T>
+struct ToV8ReturnsMaybe<std::vector<T>> {
+  static const bool value = true;
+};
+
 // Convenience functions that deduce T.
 template<typename T>
-v8::Local<v8::Value> ConvertToV8(v8::Isolate* isolate,
-                                  const T& input) {
+v8::Local<v8::Value> ConvertToV8(v8::Isolate* isolate, const T& input) {
   return Converter<T>::ToV8(isolate, input);
 }
 
@@ -253,6 +271,43 @@ inline v8::Local<v8::Value> ConvertToV8(v8::Isolate* isolate,
   return Converter<const char*>::ToV8(isolate, input);
 }
 
+template<typename T>
+v8::MaybeLocal<v8::Value> ConvertToV8(v8::Local<v8::Context> context,
+                                      const T& input) {
+  return Converter<T>::ToV8(context, input);
+}
+
+template<typename T, bool = ToV8ReturnsMaybe<T>::value> struct ToV8Traits;
+
+template <typename T>
+struct ToV8Traits<T, true> {
+  static bool TryConvertToV8(v8::Isolate* isolate,
+                             const T& input,
+                             v8::Local<v8::Value>* output) {
+    auto maybe = ConvertToV8(isolate->GetCurrentContext(), input);
+    if (maybe.IsEmpty())
+      return false;
+    *output = maybe.ToLocalChecked();
+    return true;
+  }
+};
+
+template <typename T>
+struct ToV8Traits<T, false> {
+  static bool TryConvertToV8(v8::Isolate* isolate,
+                             const T& input,
+                             v8::Local<v8::Value>* output) {
+    *output = ConvertToV8(isolate, input);
+    return true;
+  }
+};
+
+template <typename T>
+bool TryConvertToV8(v8::Isolate* isolate,
+                    T input,
+                    v8::Local<v8::Value>* output) {
+  return ToV8Traits<T>::TryConvertToV8(isolate, input, output);
+}
 inline v8::Local<v8::String> StringToV8(
     v8::Isolate* isolate,
     const base::StringPiece& input) {

native_mate/dictionary.h

@@ -10,6 +10,15 @@
 
 namespace mate {
 
+namespace internal {
+
+// Returns true if |maybe| is both a value, and that value is true.
+inline bool IsTrue(v8::Maybe<bool> maybe) {
+  return maybe.IsJust() && maybe.FromJust();
+}
+
+}  // namespace internal
+
 // Dictionary is useful when writing bindings for a function that either
 // receives an arbitrary JavaScript object as an argument or returns an
 // arbitrary JavaScript object as a result. For example, Dictionary is useful
@@ -32,27 +41,44 @@ class Dictionary {
 
   template<typename T>
   bool Get(const base::StringPiece& key, T* out) const {
-    v8::Local<v8::Value> val = GetHandle()->Get(StringToV8(isolate_, key));
+    // Check for existence before getting, otherwise this method will always
+    // returns true when T == v8::Local<v8::Value>.
+    v8::Local<v8::Context> context = isolate_->GetCurrentContext();
+    v8::Local<v8::String> v8_key = StringToV8(isolate_, key);
+    if (!internal::IsTrue(GetHandle()->Has(context, v8_key)))
+      return false;
+
+    v8::Local<v8::Value> val;
+    if (!GetHandle()->Get(context, v8_key).ToLocal(&val))
+      return false;
     return ConvertFromV8(isolate_, val, out);
   }
 
   template<typename T>
   bool GetHidden(const base::StringPiece& key, T* out) const {
-    v8::Local<v8::Value> val = GetHandle()->GetHiddenValue(
-        StringToV8(isolate_, key));
+    v8::Local<v8::Value> val =
+        GetHandle()->GetHiddenValue(StringToV8(isolate_, key));
     return ConvertFromV8(isolate_, val, out);
   }
 
   template<typename T>
   bool Set(const base::StringPiece& key, T val) {
-    return GetHandle()->Set(StringToV8(isolate_, key),
-                            ConvertToV8(isolate_, val));
+    v8::Local<v8::Value> v8_value;
+    if (!TryConvertToV8(isolate_, val, &v8_value))
+      return false;
+    v8::Maybe<bool> result =
+        GetHandle()->Set(isolate_->GetCurrentContext(),
+                         StringToV8(isolate_, key),
+                         v8_value);
+    return !result.IsNothing() && result.FromJust();
   }
 
   template<typename T>
   bool SetHidden(const base::StringPiece& key, T val) {
-    return GetHandle()->SetHiddenValue(StringToV8(isolate_, key),
-                                       ConvertToV8(isolate_, val));
+    v8::Local<v8::Value> v8_value;
+    if (!TryConvertToV8(isolate_, val, &v8_value))
+      return false;
+    return GetHandle()->SetHiddenValue(StringToV8(isolate_, key), v8_value);
   }
 
   template<typename T>