StubLSP: LSP for languages without LSP that treats file as plain text

[IvanGoncharov]

Helix splits my UX into two categories:

• Popular file formats 👍 Everything is working great with minimal setup.
• Less popular file formats (e.g. CSV, git commit messages, TXT files) 👎 No advanced features.

I need autocomplete for my workflow that works without LSP: #3328 (comment)
So I'm stuck doing local builds of #3328 that @estin heroically rebases for almost a year.
Moreover, I see other people trying to push different features to work without LSP.
Today I saw yet another one here: #3436 (comment)

I sympathize with a Helix developer's attempt to keep the architecture simple.
And it's great that all IDE-like features are delegated to LSP and implementing fallbacks for every feature increase core size.

So I have this idea: Can we have a stub LSP that is by default applied to all languages without LSP?
That stub LSP can implement all LSP-like features but treat input as plain text.
In situations where TreeSitter grammar is available, it can make StubLSP a little bit smarter (e.g. distinguish between keywords and identifiers).

In an ideal world, I would like specialized LSP plugins to existing for every file format I used
but realistically speaking StubLSP would be a great DX boost for me today.

So my question for Helix devs:

1. Do you think something like this can be a good long-term solution to support file formats without LSP?
2. Can something like StubLSP be implemented as an external repo without losing any functionality?

P.S. I would love to work on StubLSP myself, but I'm overburdened with my own OSS projects and also have zero Rust knowledge.
So this idea along with the StubLSP name can be used by anyone who wants to build PoC.

[nluetts]

Have a look at #3328 (comment)