Standalone LSP Server in Rust

[schrieveslaach]

I came across this repo based on the announcement in Nu's changelog blog and I was keen to integrate that into my Neovim setup. However, I noticed that the LSP Server is integrated into this plugin and is based on Javascript.

I'm and others (see here) not a fan of tooling written in Javascript. Therefore, I'm wondering if it is possible to create a standalone LSP, written with the aid of lsp_server or tower-lsp, in its own repo.

[fdncred]

Hey @schrieveslaach. We took the quickest route to get to something that provides more functionality than we currently have. I, for one, would love to see a standalone LSP, like you've mentioned. I kind of see this as a steppingstone to that. I am not well versed in LSPs, so I'd have to rely on others to lead the way but we'd welcome it.

[schrieveslaach]

This morning I was thinking about it and I was wondering if Nushell itself should provide an LSP backend. Maybe some sub command, such as nu language-server or something like that.

I'm imaging if this is provided and I use ctrl+o (opens your editor of choice to edit line input) my editor could start nu language-server --use-current-scope to get completions that take the current scope into account. For example, if I defined a new variable in the scope that pointed to a file and after that I typed ls into the terminal, it would be really great if the editor can suggest the variable as an argument to the ls command.

@fdncred, what do you think of integrating a language server into Nushell itself?

[jokeyrhyme]

I think the dataframe support was removed from nu itself by default due to payload size

On my system, nu is already 50MB compared to 2MB for bash, so having a full-blown LSP implementation might bloat the binary again

That said, it's also possible that there's so much shared code between normal usage of nu and the LSP (parser, etc) that wrapping an HTTP service around it doesn't actually add much more to the final payload 🤷

[fdncred]

@schrieveslaach I think having a stand-alone LSP is a good idea and I'd like to see it.

@jokeyrhyme dataframe support wasn't removed from nushell, it's feature-gated now, so, only the people who want it can compile/install with it.

[jokeyrhyme]

@fdncred that's exactly what I said

dataframe support was removed from nu itself by default

[mikayla-maki]

FWIW this is also blocking us from adding the nu LSP to Zed. I might take a crack at helping out at some later point :)

[fdncred]

FWIW this is also blocking us from adding the nu LSP to Zed. I might take a crack at helping out at some later point :)

We'd love to have your help @mikayla-maki. We're currently using a LSP-lite strategy by calling into nushell with --ide-blah parameters. Zed could use this strategy as well, but it sounds like it's not what you're looking for.

[mikayla-maki]

Oh, so your server is implemented in nu itself? That's pretty sweet. Does that mean we just have to write a little wrapper for forwarding the LSP messages to the nu command?

[mikayla-maki]

Ooh, that does seem to be how it's implemented 👀 https://github.com/nushell/vscode-nushell-lang/blob/main/server/src/server.ts#L259-L277, very cool! I might try to do that tomorrow then, it's not too dissimilar from a side project I'm working on :)

[fdncred]

yup, if you do nu --help, you'll see 5 or so --ide-something parameters. Those were all written to support our vscode integration, but it just spits out json, so it should be pretty easy to consume.

[schrieveslaach]

@fdncred, if the CLI options are already present, it should be possible to add an LSP crate on top of it. Or am I missing something?

[jokeyrhyme]

I think it's just a case of there being so much work to do and only so many maintainers/volunteers

On the plus side, there's a decent amount of prior art, including this: https://github.com/IWANABETHATGUY/tower-lsp-boilerplate

[fdncred]

@fdncred, if the CLI options are already present, it should be possible to add an LSP crate on top of it. Or am I missing something?

No, you're not missing anything really. I'm not sure our --ide-blah parameters exactly match to any LSP as I've never written an LSP. I think @jokeyrhyme is right about maintainers and time. There's also a component of, "I love to write X so I'm going to keep writing X and not Y". Open source is that way, of course.

We're definitely up for someone taking this code and building an LSP into nushell and I'm sure we'd help with it.

In fact, I was studying this code yesterday thinking the same things we're talking about. https://github.com/microsoft/qsharp/tree/main/language_service