fix: skip buffers with URI schemes in root_dir

[niklaas]

Problem

Some LSP configs implement a custom root_dir function that unconditionally
calls on_dir(project_root or vim.fn.getcwd()). When no project root is found,
this falls back to getcwd(), causing the LSP to attach to any buffer of a
matching filetype including buffers with non-file URI schemes such as
fugitive:// (vim-fugitive).

Once attached, the LSP sends requests using the fugitive:// URI, which is not
a valid file:// URI and causes errors.

The affected configs are ts_ls, tsgo, vtsls, and matlab_ls.

Configs that use root_markers only (e.g. lua_ls, ruby_lsp) are naturally
safe because vim.fs.root() returns nil for non-file buffers, so on_dir is
never called.

Solution

Add a guard at the top of each affected root_dir function that returns early
when the buffer name starts with a URI scheme:

if vim.api.nvim_buf_get_name(bufnr):match('^%a+://') then
    return
end

From my understanding, neovim buffer names are always plain paths (e.g.
/home/user/file.ts) for real files, never file:// URIs, so this guard only
skips genuinely non-file buffers.

I don't think the early returns trigger false positives but for sure let me know if they do.

[justinmk]

Thanks for the clear explanation. But I don't quite see why the solution was chosen.

I think it's more like a hint that getcwd() should not be used as a fallback. People really seem to love it though ...

[niklaas]

I think it's more like a hint that getcwd() should not be used as a fallback.

Good catch, I agree. I guess I subconsciously decided to use a guard to avoid introducing a breaking change.

However, I'm happy to remove calling getcwd(). As you indicate, arguably, the issue I ran into demonstrates the function isn't the proper approach to choose there because it's brittle.

Let me know if you'd be willing to introduce a breaking change.

[justinmk]

From my understanding, neovim buffer names are always plain paths (e.g.
/home/user/file.ts) for real files, never file:// URIs

That may change in the future though.

I guess you could future-proof your current PR by only skipping if is_uri and root() == nil

[igorlfs]

Using vim.uv.fs_stat might be preferable here? See #3899