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 = " ",
  EnumMember = " ",
  Field = "󰄶 ",
  File = " ",
  Folder = " ",
  Function = " ",
  Interface = "󰜰",
  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)
  bufnr = bufnr or 0
  line_nr = line_nr or (vim.api.nvim_win_get_cursor(0)[1] - 1)
  opts = opts or {['lnum'] = line_nr}

  local line_diagnostics = vim.diagnostic.get(bufnr, opts)
  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.api.nvim_create_autocmd("CursorHold", {
  group = vim.api.nvim_create_augroup("print_diagnostics", { clear = true }),
  callback = 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.api.nvim_create_autocmd({ "CursorHold", "CursorHoldI" }, {
  group = vim.api.nvim_create_augroup("float_diagnostic", { clear = true }),
  callback = function ()
    vim.diagnostic.open_float(nil, {focus=false})
  end
})

For diagnostics for specific cursor position

vim.api.nvim_create_autocmd({ "CursorHold", "CursorHoldI" }, {
  group = vim.api.nvim_create_augroup("float_diagnostic_cursor", { clear = true }),
  callback = function ()
    vim.diagnostic.open_float(nil, {focus=false, scope="cursor"})
  end
})

After neovim 0.7, put the code below into on_attach()

vim.api.nvim_create_autocmd("CursorHold", {
  buffer = bufnr,
  callback = function()
    local opts = {
      focusable = false,
      close_events = { "BufLeave", "CursorMoved", "InsertEnter", "FocusLost" },
      border = 'rounded',
      source = 'always',
      prefix = ' ',
      scope = 'cursor',
    }
    vim.diagnostic.open_float(nil, opts)
  end
})

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))
        vim.fn.setqflist(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

vim.diagnostic.config({
  virtual_text = {
    source = "always",  -- Or "if_many"
  },
  float = {
    source = "always",  -- Or "if_many"
  },
})

Change prefix/character preceding the diagnostics' virtual text

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

vim.diagnostic.config({
  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.

for _, diag in ipairs({ "Error", "Warn", "Info", "Hint" }) do
    vim.fn.sign_define("DiagnosticSign" .. diag, {
        text = "",
        texthl = "DiagnosticSign" .. diag,
        linehl = "",
        numhl = "DiagnosticSign" .. diag,
    })
end

Depending on how your theme is styled, you may wish to replace the prefix for numhl with "DiagnosticVirtualText" or "DiagnosticFloating" to better fit the intended look.

Highlight symbol under cursor

Add the following to your on_attach (this allows checking server capabilities to avoid calling invalid commands).

if client.resolved_capabilities.document_highlight then
  vim.cmd [[
    hi! LspReferenceRead cterm=bold ctermbg=red guibg=LightYellow
    hi! LspReferenceText cterm=bold ctermbg=red guibg=LightYellow
    hi! LspReferenceWrite cterm=bold ctermbg=red guibg=LightYellow
  ]]
  vim.api.nvim_create_augroup('lsp_document_highlight', {
    clear = false
  })
  vim.api.nvim_clear_autocmds({
    buffer = bufnr,
    group = 'lsp_document_highlight',
  })
  vim.api.nvim_create_autocmd({ 'CursorHold', 'CursorHoldI' }, {
    group = 'lsp_document_highlight',
    buffer = bufnr,
    callback = vim.lsp.buf.document_highlight,
  })
  vim.api.nvim_create_autocmd({ 'CursorMoved', 'CursorMovedI' }, {
    group = 'lsp_document_highlight',
    buffer = bufnr,
    callback = vim.lsp.buf.clear_references,
  })
end

Note this requires Neovim v0.7 which introduces vim.api.nvim_create_augroup and vim.api.nvim_create_autocmd. If you are using Neovim with version prior to v0.7 then use the following:

Click to expand

if client.resolved_capabilities.document_highlight then
  vim.cmd [[
    hi! LspReferenceRead cterm=bold ctermbg=red guibg=LightYellow
    hi! LspReferenceText cterm=bold ctermbg=red guibg=LightYellow
    hi! LspReferenceWrite cterm=bold ctermbg=red guibg=LightYellow
    augroup lsp_document_highlight
      autocmd! * <buffer>
      autocmd! CursorHold <buffer> lua vim.lsp.buf.document_highlight()
      autocmd! CursorHoldI <buffer> lua vim.lsp.buf.document_highlight()
      autocmd! CursorMoved <buffer> lua vim.lsp.buf.clear_references()
      autocmd! CursorMovedI <buffer> lua vim.lsp.buf.clear_references()
    augroup END
  ]]
end

If you are on Neovim v0.8, client.resolved_capabilities.document_highlight is deprecated. In its place, use client.server_capabilities.documentHighlightProvider.