Watch kernel and runtime directories for updates

[rgbkrk]

We could use fs.watch to track kernel installations (or other runtimes being launched, e.g. the notebook). To make this simpler, there are higher level watch libraries like https://github.com/mikeal/watch or https://github.com/bevry/watchr.

This would make it so it isn't just determined once on startup, but asynchronously throughout use.

[BenRussert]

@rgbkrk I wonder if (almost two years later) you have any more thoughts on this? Is there anything in the nteract repo that might be a good model?

[rgbkrk]

Sidecar detects new runtime directories, though the code has grown stale (no one hacking on it, lots of outdated libraries, no shared knowledge of what's going on in there). For Hydrogen, I'd write the kernel checking all over again or make it part of kernelspecs.

[lgeiger]

👍 For using kernelspecs!

Though at the moment it doesn't detect the default python installation so users need to run python -m ipykernel install --user so it can be detected.

I'm wondering if the easiest thing would be, if kernelspecs ran python -m ipykernel install --user if it can't detect a python kernel and then rerun current detection method.

[rgbkrk]

We could bring the default python detection to kernelspecs though, which is currently buried away in old PRs of mine on nteract/nteract that I've closed.

[lgeiger]

We could bring the default python detection to kernelspecs though, which is currently buried away in old PRs of mine on nteract/nteract that I've closed.

Ahh sure I forgot!

For reference: nteract/nteract#1384

[lgeiger]

Atom now has a file watching API. Since we're now using kernelspecs we could easily watch the directories returned by jupyter-paths for changes and update the kernels.

I'd be very happy if someone is interested in implementing this.