GeezerVison

Do you mean these run in parallel?

No, their napi_finalize callbacks can be run in an interleaving pattern, on the JavaScript thread.

Can you expand a bit here? Is the suggestion to use the hooks instead of napi_finalize callback?

This part is specifically focused on the finalization at shutdown. Still, addons should set an napi_finalize callback to finalize the native objects properly.

However, their napi_finalize callbacks can be run in an interleaving pattern forcefully, regardless of if they are actually referenced. This would lead to the problem mentioned in nodejs/node-addon-api#1109:

Normally, we expect the order to be:

1. create an ObjectWrap,
2. create a ThreadSafeFunction and save it to a field of that ObjectWrap,
3. release the ObjectWrap,
4. release the ThreadSafeFunction in the ~ObjectWrap.

However, when the environment is shutting down, the order would be:

1. create an ObjectWrap,
2. create a ThreadSafeFunction and save it to a field of that ObjectWrap,
3. env shutdown, run napi_finalize in reversed creation order,
4. release the ThreadSafeFunction,
5. release the ObjectWrap => crash as the ThreadSafeFunction has already been finalized.

@legendecas Does this mean that I am supposed to maintain a central directory of all ThreadSafeFunction by environment so that I can Release in the cleanup hook because by the time the ObjectWrap destructor is called, it would be too late?

@legendecas in particular, if I use napi_add_async_cleanup_hook, can I delay the destruction of the environment until all ObjectWraps has been destroyed? Ie, will the destructors get called while Node is waiting for napi_remove_async_cleanup_hook? I strongly suggest that you do at least this, because otherwise this would mean that all ObjectWraps are to have a two-staged destruction with a C++ destructor and a, lets call it ::Destroy(), method which can be called both from the destructor and the environment cleanup hook. This would throw out of the window all the work done on the clean node-addon-api interface which aligns the JS object lifecycle with the C++ constructor/destructor.

@mmomtchev Does this mean that I am supposed to maintain a central directory of all ThreadSafeFunction by environment so that I can Release in the cleanup hook because by the time the ObjectWrap destructor is called, it would be too late?

If the ThreadSafeFunction is saved as a field of a c++ ObjectWrap, it should be released in the destructor of the ObjectWrap. So it is sufficient for an add-on to keep track of ObjectWraps and released them in a napi_cleanup_hook.

in particular, if I use napi_add_async_cleanup_hook, can I delay the destruction of the environment until all ObjectWraps has been destroyed? Ie, will the destructors get called while Node is waiting for napi_remove_async_cleanup_hook?

This is how napi_async_cleanup_hook_handle works now. If an napi_async_cleanup_hook_handle is still pending removal by napi_remove_async_cleanup_hook, the napi_env is not going to be destructed. This is verified with tests at #46692.