Displaying virtual text at the end of the line, rather than below the error

[ernstki]

I'm using Vim 9.1 from MacPorts, and this seems like a thing that should be possible with an LSP plugin.

But is it actually doable with Vim 9.x, without a lot of crazy configuration? I didn't notice any mention of it in the vim-lsp docs, or in the discussions, and the only examples I've seen in the wild are people using NeoVim or LunarVim (which is just NeoVim).

The vim-lsp docs say this:

g:lsp_diagnostics_virtual_text_enabled
    Type: Number
    Default: 1 for neovim 0.3+

    Enables virtual text to be shown next to diagnostic errors. Requires
    NeoVim with version 0.3 or newer or Vim with virtual-text and
    patch 9.0.0178, and g:lsp_diagnostics_enabled set to 1.
    Virtual text uses the same highlight groups used for signs (eg LspErrorText),
    but can be uniquely defined if you want to have different highlight groups
    for signs and virtual text. To set unique virtual text highlighting, you
    can set or link LspErrorVirtualText, LspWarningVirtualText,
    LspInformationVirtualText and LspHintVirtualText highlight groups.

…and my Vim seems to meet all those criteria, but I still get diagnostics below the errors, not to the right of them. Even with all the work that I presume went into debouncing, this just isn't a good experience when you're editing lines below some active errors.

I did a decent amount of using my human brain and looking around before resorting to asking a GPT for help, and here's what it came up with.

autocmd User lsp_setup call lsp#register_server({
    \ 'name': 'your_language_server',
    \ 'cmd': {server_info->['path/to/your/language-server']},
    " ⋮
    \ 'on_diagnostics': function('s:on_diagnostics'),
    \ })

function! s:on_diagnostics(_, params)
    " Get the diagnostics
    let l:diagnostics = params['diagnostics']
    for l:diagnostic in l:diagnostics
        " Adjust the position to the end of the line
        let l:line = l:diagnostic['range']['end']['line']
        let l:char = l:diagnostic['range']['end']['character']
        let l:message = l:diagnostic['message']
        " Display virtual text at the end of the line
        call nvim_buf_set_virtual_text(0, -1, l:line, [[l:message]], {})
    endfor
endfunction

Seems plausible, and it appears to be error-free (at least my Vim doesn't crash on startup). However, the question I'm left with is how do I apply that s:ondiagnostics to every language for which a language server is available.

[ernstki]

I even read vim/vim#7553 as far as I could, but it got over my head pretty quick.

[ernstki]

The solution is—you guessed it—in the help. The default alignment for virtual text is below. From the docs as of this writing:

g:lsp_diagnostics_virtual_text_align    g:lsp_diagnostics_virtual_text_align
    Type: String
    Default: "below"

    Determines the align of the diagnostics virtual text. Requires
    g:lsp_diagnostics_virtual_text_enabled.

    Possible values are:

       after   after the end of the line
       right   right aligned in the window (unless the text wraps to the next
               screen line)
       below   in the next screen line
       above   just above the line

    Only one "right" property can fit in each line, if there are two or more
    these will go in a separate line (still right aligned).

    This value is passed as the "text_align" property in a prop_add() call.

    Example:
        let g:lsp_diagnostics_virtual_text_align = "right"

Solution

Add this to your ~/.vimrc, inside the augroup lsp_install that you presumably copied from the README:

augroup lsp_install
    au!
    " call s:on_lsp_buffer_enabled only for languages that has the server registered.
    autocmd User lsp_buffer_enabled call s:on_lsp_buffer_enabled()

    " see: https://github.com/prabirshrestha/vim-lsp/discussions/1582
    " options are: after, right, below(*), above  (*default)
    let g:lsp_diagnostics_virtual_text_align = 'right'
augroup END