How to implement custom inspect into ObjectWrap class? #919

Activity

1. KevinEady commented on Mar 3, 2021

   

   KevinEady

   on Mar 3, 2021

   Contributor

   More actions

   Have you tried Napi::Symbol::WellKnown? Otherwise, you could either pass the JavaScript value of Symbol.for(...) to your addon so it can be used, or you can grab it from global, something like:

   auto Symbol = env.Global().Get("Symbol").As<Object>();
   auto inspectSym = Symbol.Get("for").As<Function>().Call(Symbol, { Napi::String::New(env, "nodejs.util.inspect.custom") });
2. ThomasWeinert commented on Mar 3, 2021

   

   ThomasWeinert

   on Mar 3, 2021

   Last edited by ThomasWeinert

   Author

   More actions

   Napi::Symbol::WellKnown(env, "nodejs.util.inspect.custom") returns Napi::Env::Undefined().

   Fetching it from JS works. I put that into a utility function:

   Napi::Symbol GetPublicSymbol(const Napi::Env &env, std::string name) {
       auto Symbol = env.Global().Get("Symbol").As<Napi::Object>();
       auto forSymbol = Symbol.Get("for").As<Napi::Function>().Call(
           Symbol, { Napi::String::New(env, name) }
       );
       return forSymbol.As<Napi::Symbol>();
   }

   And then

   InstanceMethod(GetPublicSymbol(env, "nodejs.util.inspect.custom"), &MyObjectWrap::Inspect),

   Thank you.
3. gabrielschulhof commented on Mar 5, 2021

   

   gabrielschulhof

   on Mar 5, 2021

   Contributor

   More actions

   @KevinEady is it a problem with Napi::Symbol::WellKnown that it returns undefined in this case?
4. KevinEady commented on Mar 26, 2021

   

   KevinEady

   on Mar 26, 2021

   Contributor

   More actions

   @KevinEady is it a problem with Napi::Symbol::WellKnown that it returns undefined in this case?

   @gabrielschulhof hmmm... the implementation for WellKnown is:
   

   node-addon-api/napi-inl.h

   Lines 996 to 998 in 8ef0725

   	inline Symbol Symbol::WellKnown(napi_env env, const std::string& name) {
   	return Napi::Env(env).Global().Get("Symbol").As<Object>().Get(name).As<Symbol>();
   	}

   This is the equivalent of:

   Symbol[name]

   Which is different than

   Symbol.for(name)

   Is the WellKnown implementation incorrect?
5. KevinEady commented on Apr 16, 2021

   

   KevinEady

   on Apr 16, 2021

   Contributor

   More actions

   As discussed in the Node-API meeting, the implementation for Symbol::WellKnown is correct: it is used to retrieve values like Symbol.toStringTag, which is a direct property on Symbol.

   Closing issue.
6. KevinEady

   closed this as completedon Apr 16, 2021