Benricheson101

local function hl_extend(name, val)
  local hl = vim.api.nvim_get_hl(0, {name = name, create = true});
  local new = vim.tbl_deep_extend('force', {}, hl, val)
  vim.api.nvim_set_hl(0, name, new)
end

for _, type in ipairs {'Ok', 'Info', 'Hint', 'Warn', 'Error'} do
  hl_extend('DiagnosticUnderline' .. type, {undercurl = true})
end