N-API: unable to perform on completion callback through napi_env

[Aerrus-zz]

• Node.js Version: 11.11.0
• OS: Mac
• Scope (install, code, runtime, meta, other?): runtime
• Module (and version) (if relevant): node-addon-api 1.6.2

Seen a few threads about the why napi_get_current_env() was removed. Seen the rationale behind it and how the api will simply be designed to revolve around it.

However, it doesn't seem like it's possible to pass in napi_env to a C++ lambda that fires after a long completing task. Use case is that I need to call the long task and make a callback to a JS function that updates the UI accordingly.

napi_value somefunc(napi_env env, napi_callback_info cbinfo) {
    someLongFunc("yay", [env](int num) {
            napi_value test;
            napi_status s = napi_create_string_utf8(env, "moretest", NAPI_AUTO_LENGTH, &test);
            //check status, make callback, etc.
        });
    return nullptr;
}

Running this gives EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) on the create string line, which as far as I can tell, can be caused by bad access to napi_env.

I have considered the napi async work way, but I cannot use that since my long running function has to be on the UI thread and async work creates a new thread to run the execute and complete functions from.

[mhdawson]

Have you looked at the thread_save_function_calls that have been added to the core API?https://nodejs.org/docs/latest/api/n-api.html#n_api_asynchronous_thread_safe_function_calls I think they might be what you need.

[Aerrus-zz]

This is very close to what I need. Thanks!
However I don't see a simple way to make the callback with any input parameters, my long running function will eventually create a napi_value(string) to use in napi_call_function to make the callback (the JS callback just prints the string out).