Get a language server working

[bollwyvl]

Elevator Pitch

At least one language server should work.

Motivation

Not very fun otherwise.

Design Ideas

• yaml-language-server seems like it's getting close,
  • but anything, really, that demos

[qqdaiyu55]

It will be HUGE if we can use jupyterlab-lsp on jupyterlite. Very promising! THANKS!

[bollwyvl]

There is now a final version of jupyterlab-lsp 5.0.0 available, so this work could continue, as it will now be possible to install a mutually-compatible constellation of jupyterlab, jupyterlite-core, and jupyterlite-lsp (previously, jupyterlab-lsp decided to go 3.6+, which jupyterlite didn't adopt, due to breaking changes, only now partially resolved in the 0.2.x line).

It would be ideal if the yaml-language-server revved its underlying dependencies so we weren't working with outdated LSP specs.

Once a single, out-of-kernel language server works, it might be another slog to get something working against a non-trivial kernel storage (e.g. not synced to contents). One way I can imagine is by something like jupyter-lsp/jupyterlab-lsp#278, which moves the JSON-RPC pipe from a dedicated mock "websocket" to Jupyter comms, but that branch is very bitrotted at this point, and might require even more monkeypatching craziness.