In terms of the JavaScript spec, you are performing a [[Set]] operation
with `dict[x] = x`. The key for [[Set]] must be a valid property key, which
is either a String or a Symbol. In this case, the code actually looks more
like `dict[x.toString()] = x`. This is just how JavaScript works, and is
intended.
On Thu, Sep 26, 2019 at 8:07 AM Gautham B A <gautham.bangal...@gmail.com>
wrote:
> Hi all,
>
> Calling IsFunction() on v8::Local<v8::Name> is returning false, even
> though v8::Local<v8::Name> was pointing to a function in JavaScript. Is
> this expected? Consider the following code -
>
> #include <iostream>
> #include <libplatform/libplatform.h>
> #include <ostream>
> #include <v8.h>
>
>
> void Getter(v8::Local<v8::Name> key,
> const v8::PropertyCallbackInfo<v8::Value> &info) {
> std::cout << "Getter:" << std::endl;
> std::cout << "IsFunction: " << key->IsFunction() << std::endl;
> }
>
>
> void Setter(v8::Local<v8::Name> key, v8::Local<v8::Value> value,
> const v8::PropertyCallbackInfo<v8::Value> &info) {
> std::cout << "Setter:" << std::endl;
> // key->IsFunction() returns false, expected to be true
> std::cout << "Key IsFunction: " << key->IsFunction() << std::endl;
>
>
> // value->IsFunction() returns true, as expected
> std::cout << "\nValue IsFunction:" << value->IsFunction() << std::endl;
> }
>
>
> void Deleter(v8::Local<v8::Name> key,
> const v8::PropertyCallbackInfo<v8::Boolean> &info) {}
>
>
> bool InstallMap(v8::Isolate *isolate, const v8::Local<v8::Context> &
> context) {
> v8::HandleScope handle_scope(isolate);
> auto obj_template = v8::ObjectTemplate::New(isolate);
> obj_template->SetHandler(
> v8::NamedPropertyHandlerConfiguration(Getter, Setter, nullptr,
> Deleter));
>
>
> v8::Local<v8::Object> obj;
> if (!obj_template->NewInstance(context).ToLocal(&obj)) {
> std::cerr << "Unable to instantiate object template" << std::endl;
> return false;
> }
>
>
> v8::Local<v8::String> obj_name;
> if (!v8::String::NewFromUtf8(isolate, "dict", v8::String::kNormalString)
> ->ToString(context)
> .ToLocal(&obj_name)) {
> std::cerr << "Unable to create map key name" << std::endl;
> return false;
> }
>
>
> auto global = context->Global();
> if (!global->Set(context, obj_name, obj).FromJust()) {
> std::cerr << "Unable to install object into global scope" << std::endl
> ;
> return false;
> }
> return true;
> }
>
>
> int main(int argc, char *argv[]) {
> const auto script_str = R"(
> function x() {
> }
>
>
> dict[x] = x;
> )";
>
>
> v8::V8::InitializeICUDefaultLocation(argv[0]);
> v8::V8::InitializeExternalStartupData(argv[0]);
> auto platform = v8::platform::NewDefaultPlatform();
> v8::V8::InitializePlatform(platform.get());
> v8::V8::Initialize();
>
>
> v8::Isolate::CreateParams create_params;
> create_params.array_buffer_allocator =
> v8::ArrayBuffer::Allocator::NewDefaultAllocator();
> v8::Isolate *isolate = v8::Isolate::New(create_params);
> {
> v8::Isolate::Scope isolate_scope(isolate);
> v8::HandleScope handle_scope(isolate);
> auto context = v8::Context::New(isolate);
> v8::Context::Scope context_scope(context);
>
>
> InstallMap(isolate, context);
>
>
> auto source =
> v8::String::NewFromUtf8(isolate, script_str, v8::NewStringType::
> kNormal)
> .ToLocalChecked();
> auto script = v8::Script::Compile(context, source).ToLocalChecked();
> auto result = script->Run(context).ToLocalChecked();
> v8::String::Utf8Value result_utf8(isolate, result);
> std::cout << *result_utf8 << std::endl;
> }
> isolate->Dispose();
> v8::V8::Dispose();
> v8::V8::ShutdownPlatform();
> delete create_params.array_buffer_allocator;
> return 0;
> }
>
>
> As seen in the code above, I'm exposing a global variable dict which has
> the Setter, Getter and Deleter callbacks set appropriately on dict.
>
> function x() {
> }
> dict[x] = x;
> When I run the above JavaScript code, The Setter callback gets called and
> I see that *name* and *value* have different results upon calling
> IsFunction() on them.
> Could someone please tell me if this is the expected behavior, if so, the
> reason behind why it is so?
>
> Thanks,
> --Gautham
>
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