UI Customization

Note: these instruction assume Neovim 0.6.0 or later!

Borders

Floating windows with borders are built-into the neovim core handler. The borders can be styled by passing in a character and highlight group. Highlight groups must be set with an autocmd to avoid being overwritten by your colorscheme.

vim.cmd [[autocmd ColorScheme * highlight NormalFloat guibg=#1f2335]]
vim.cmd [[autocmd ColorScheme * highlight FloatBorder guifg=white guibg=#1f2335]]

local border = {
      {"🭽", "FloatBorder"},
      {"▔", "FloatBorder"},
      {"🭾", "FloatBorder"},
      {"▕", "FloatBorder"},
      {"🭿", "FloatBorder"},
      {"▁", "FloatBorder"},
      {"🭼", "FloatBorder"},
      {"▏", "FloatBorder"},
}

-- LSP settings (for overriding per client)
local handlers =  {
  ["textDocument/hover"] =  vim.lsp.with(vim.lsp.handlers.hover, {border = border}),
  ["textDocument/signatureHelp"] =  vim.lsp.with(vim.lsp.handlers.signature_help, {border = border }),
}

-- Do not forget to use the on_attach function
require 'lspconfig'.myserver.setup { handlers=handlers }

-- To instead override globally
local orig_util_open_floating_preview = vim.lsp.util.open_floating_preview
function vim.lsp.util.open_floating_preview(contents, syntax, opts, ...)
  opts = opts or {}
  opts.border = opts.border or border
  return orig_util_open_floating_preview(contents, syntax, opts, ...)
end

require 'lspconfig'.myservertwo.setup {}

Completion kinds

local M = {}

M.icons = {
  Class = " ",
  Color = " ",
  Constant = " ",
  Constructor = " ",
  Enum = "了 ",
  EnumMember = " ",
  Field = " ",
  File = " ",
  Folder = " ",
  Function = " ",
  Interface = "ﰮ ",
  Keyword = " ",
  Method = "ƒ ",
  Module = " ",
  Property = " ",
  Snippet = "﬌ ",
  Struct = " ",
  Text = " ",
  Unit = " ",
  Value = " ",
  Variable = " ",
}

function M.setup()
  local kinds = vim.lsp.protocol.CompletionItemKind
  for i, kind in ipairs(kinds) do
    kinds[i] = M.icons[kind] or kind
  end
end

return M

Customizing how diagnostics are displayed

You can configure diagnostic options globally. See :help vim.diagnostic.config for more advanced customization options.

vim.diagnostic.config({
  virtual_text = true,
  signs = true,
  underline = true,
  update_in_insert = false,
  severity_sort = false,
})

Note: With the default settings, you will not see updated diagnostics until you leave insert mode. Set update_in_insert = true if you want diagnostics to update while in insert mode.

Change diagnostic symbols in the sign column (gutter)

local signs = { Error = " ", Warn = " ", Hint = " ", Info = " " }
for type, icon in pairs(signs) do
  local hl = "DiagnosticSign" .. type
  vim.fn.sign_define(hl, { text = icon, texthl = hl, numhl = hl })
end

Print diagnostics to message area

function PrintDiagnostics(opts, bufnr, line_nr, client_id)
  opts = opts or {}

  bufnr = bufnr or 0
  line_nr = line_nr or (vim.api.nvim_win_get_cursor(0)[1] - 1)

  local line_diagnostics = vim.lsp.diagnostic.get_line_diagnostics(bufnr, line_nr, opts, client_id)
  if vim.tbl_isempty(line_diagnostics) then return end

  local diagnostic_message = ""
  for i, diagnostic in ipairs(line_diagnostics) do
    diagnostic_message = diagnostic_message .. string.format("%d: %s", i, diagnostic.message or "")
    print(diagnostic_message)
    if i ~= #line_diagnostics then
      diagnostic_message = diagnostic_message .. "\n"
    end
  end
  vim.api.nvim_echo({{diagnostic_message, "Normal"}}, false, {})
end

vim.cmd [[ autocmd CursorHold * lua PrintDiagnostics() ]]

Show line diagnostics automatically in hover window

-- You will likely want to reduce updatetime which affects CursorHold
-- note: this setting is global and should be set only once
vim.o.updatetime = 250
vim.cmd [[autocmd CursorHold,CursorHoldI * lua vim.diagnostic.open_float(nil, {focus=false})]]

For diagnostics for specific cursor positio

vim.cmd [[autocmd CursorHold,CursorHoldI * lua vim.diagnostic.open_float(nil, {focus=false, scope="cursor"})]]

Filter by severity in signcolum

See https://www.reddit.com/r/neovim/comments/mvhfw7/can_built_in_lsp_diagnostics_be_limited_to_show_a/

Go-to definition in a split window

local function goto_definition(split_cmd)
  local util = vim.lsp.util
  local log = require("vim.lsp.log")
  local api = vim.api

  -- note, this handler style is for neovim 0.5.1/0.6, if on 0.5, call with function(_, method, result)
  local handler = function(_, result, ctx)
    if result == nil or vim.tbl_isempty(result) then
      local _ = log.info() and log.info(ctx.method, "No location found")
      return nil
    end

    if split_cmd then
      vim.cmd(split_cmd)
    end

    if vim.tbl_islist(result) then
      util.jump_to_location(result[1])

      if #result > 1 then
        util.set_qflist(util.locations_to_items(result))
        api.nvim_command("copen")
        api.nvim_command("wincmd p")
      end
    else
      util.jump_to_location(result)
    end
  end

  return handler
end

vim.lsp.handlers["textDocument/definition"] = goto_definition('split')

Show source in diagnostics (neovim 0.6+ only)

vim.lsp.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(vim.lsp.diagnostic.on_publish_diagnostics, {
  virtual_text = {
    source = "always",  -- Or "if_many"
  }
})

Change prefix/character preceding the diagnostics' virtual text

By default, this character is a square icon (■).

vim.lsp.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(vim.lsp.diagnostic.on_publish_diagnostics, {
  virtual_text = {
    prefix = '■', -- Could be '●', '▎', 'x'
  }
})

Highlight line number instead of having icons in sign column

See the properties of the signs with sign list.

vim.cmd [[
  highlight DiagnosticLineNrError guibg=#51202A guifg=#FF0000 gui=bold
  highlight DiagnosticLineNrWarn guibg=#51412A guifg=#FFA500 gui=bold
  highlight DiagnosticLineNrInfo guibg=#1E535D guifg=#00FFFF gui=bold
  highlight DiagnosticLineNrHint guibg=#1E205D guifg=#0000FF gui=bold

  sign define DiagnosticSignError text= texthl=DiagnosticSignError linehl= numhl=DiagnosticLineNrError
  sign define DiagnosticSignWarn text= texthl=DiagnosticSignWarn linehl= numhl=DiagnosticLineNrWarn
  sign define DiagnosticSignInfo text= texthl=DiagnosticSignInfo linehl= numhl=DiagnosticLineNrInfo
  sign define DiagnosticSignHint text= texthl=DiagnosticSignHint linehl= numhl=DiagnosticLineNrHint
]]