Update node_api modules at src/ with threadsafe functionality

[markBETA]

Hi to everyone!

I have tried to compile with the last update with the ThreadSafeFunction class but it seems that the node_api modules at the src/ folder are not updated with the threadsafe functionality.
I think that is needed to update these files for using the new functionality.

[mhdawson]

Those files should not be being used for any active LTS version. Instead the code being used should come from the Node runtime.

[gabrielschulhof]

@mhdawson we need to drop the N-API implementation from node-addon-api once v8.x becomes unmaintained.

[mhdawson]

@gabrielschulhof agreed :)

[mhdawson]

@markBETA I had meant to ask what version of Node are you using. I see that I missed that in my first post.

[markBETA]

@mhdawson I tried to use the source files from the Node runtime and it worked! I'm using the last LTS version (10.16.0), where the threadsafe operations are marked as stable.

I'm working with Cmake-JS to compile the source files of my addon. I think it will be good to specify in the readme to use the files from the Node runtime. As @gabrielschulhof said, I think it will be good to remove the src/ folder that is not maintained anymore.

[mhdawson]

@markBETA thanks. By default if you use node-gyp it will find the right files but seems like for other cases we need more doc. Any chance you'd be able to submit a PR to the README.md to add what you would have found useful?

Yes the src folder with old files is highly confusing. Would be nice to have it deleted.

[marco-ms]

Hi,
I am also exploring node-addon-api v1.7.1 and ThreadSafeFunction. Sorry if I am off topic, but I got a bit overwhelmed regarding documentation and compatibility matrix, I'll make some statements, feel free to correct me, whenever they are incorrect.

1. I understand that to work ThreadSafeFunction requires N-API 4
2. N-API 4 is supported by: Node 8.16.0+, 11.8.0+ or 12.0.0+
   https://nodejs.org/docs/latest-v12.x/api/n-api.html#n_api_n_api_version_matrix
3. If you have a Node that supports N-API 3 you can still build correctly, but you need N-API 4 support to run it (the phrase in that url leaves a bit to interpretation).
4. If I am using my add-on onto Electron, I need an Electron version that runs at least a Node version taken from list in point 2.
5. Which Node exactly is running Electron 3.1? All I could find is Electron 3.1 forked from Electron 3.0 which is running Node 10.2.0 https://electronjs.org/blog/electron-3-0 (unsure)
6. Electron 3.x does NOT support N-API 4
7. Even if I compile my node module with N-API 4 compatible Node (say Node 8.16.0), running on Electron 3.x won't make ThreadSafeFunction to work (possibly won't even run?)
8. If all my previous statements are correct, what are my options if N-API 4 is not supported to actually syncronize a native callback back to the main thread in order to post results to JavaScript? If I remove it currently my node add-on crashes, so I need a solution.

@mhdawson looking at this documentation[1] I find very hard if not impossible to get the correct information regarding "API X will work with my Electron Y.Z"? It looks to me like a maze, but maybe is because new to this API.

[1] https://github.com/nodejs/node-addon-api/blob/master/doc/threadsafe_function.md

Thank you so much for your attention and sorry if this is off topic.

[mhdawson]

Unfortunately, I'm not up to speed on the mapping between Node versions and Electron. Maybe @codebytere can help.

If you have a Node that supports N-API 3 you can still build correctly, but you need N-API 4 support to run it (the phrase in that url leaves a bit to interpretation).

I don't think this is the case. You need a Node.js version which supports N-API 4 to build using N-API v4 features. The exception is if you enable EXPERIMENTALly and those features were EXPERIMENTAL in the earlier Node.js version. In which case you may build but them later not run if in a Node.js version that does not support v4 features (or have the feature as EXPERIMENTAL)

If all my previous statements are correct, what are my options if N-API 4 is not supported to actually syncronize a native callback back to the main thread in order to post results to JavaScript? If I remove it currently my node add-on crashes, so I need a solution.

Unfortunately, there won't be a great answer to this. We've added the ThreadSafeFunction as it became apparent that it was a common use case. You might be able to look at the methods within the C N-API and implement those yourself, but that will likely mean using internal APIs and that the native module would need ot be re-compiled for each version of Node.js (although that's no worse than without N-API). Not sure how easy it will be to bridge between the non N-API and N-API code required to do that either.