fix(lsp): not reuse lsp client for standalone file

[Bacbia3696]

If I open first standalone rust file, all lsp function work as expected, but when I open the second file. It will reuse lsp client for this second file, so all the lsp function is not supported.

Because vim.lsp.start will reuse lsp client if we start the the same root_dir (which is nil in this case)

This PR will check if root_dir == nil, we not reuse lsp client

I also update ftplugin to prevent start function run twice.

[github-actions]

Review Checklist

Does this PR follow the Contribution Guidelines? Following is a partial checklist:

Proper conventional commit scoping:

• For example, fix(lsp): some lsp-related bugfix

• Pull request title has the appropriate conventional commit prefix.

If applicable:

• Tested
  • Tests have been added.
  • Tested manually (Steps to reproduce in PR description).
• Updated documentation.
• Updated CHANGELOG.md

[mrcjkb]

Hey 👋

Thanks for the PR!

I've tested this, and it will spawn a separate rust-analyzer process for every standalone rust file opened.

I'll think about this and see if I can come up with an alternate solution.

Update: We need to wait for rust-lang/rust-analyzer#14318 to be resolved, before we can implement a proper fix:

// FIXME: The primary limitation of this approach is that the set of detached files needs to be fixed at the beginning. 
// That's not the end user experience we should strive for. 

I don't think spawning a separate rust-analyzer process for each standalone file is a good workaround, because it could easily get out of hand.

What you can do as a workaround is run :RustAnalyzer restart, and it will pick up the new detached file (but not the old one).

[mrcjkb]

I've implemented a fix for setting up the vim.lsp.commands for rust-analyzer only once in a24df27

and a fix for doing ftplugin stuff in a503d05