Neovim augroup and autocommand in lua (relative line numbering)

Question

I'm converting my init.vim into a set of lua config files, called from init.lua I'm trying to convert this from init.vim

augroup numbertoggle
  autocmd!
  autocmd BufEnter,FocusGained,InsertLeave * set relativenumber
  autocmd BufLeave,FocusLost,InsertEnter   * set norelativenumber
augroup END

to this in set.lua (loaded from init.lua)

local numtogGrp = vim.api.nvim_create_augroup("NumberToggle", { clear = true })
vim.api.nvim_create_autocmd(
  { "BufEnter", "InsertLeave", "FocusGained"},
  { pattern = "*",
    --command = "set relativenumber",  -- if callback, vim.api.nvim_buf_set_option(0,relativenumber,true) ?
    callback = function()
      vim.api.nvim_buf_set_option(0, 'relativenumber', true)
    end,
    group = numtogGrp,
    desc = "Turn on relative line numbering when the buffer is entered.",
  }
)
vim.api.nvim_create_autocmd(
  { "BufLeave", "InsertEnter", "FocusLost"},
  { pattern = "*",
    --command = "set norelativenumber",
    callback = function()
      vim.api.nvim_buf_set_option(0, 'relativenumber', false)
    end,
    group = numtogGrp,
    desc = "Turn off relative line numbering when the buffer is exited.",
  }
)

No errors when I source the file, but when any of the events occur I get 'Invalid option name 'relativenumber' Finally I realised I needed vim.api.nvim_set_option('relativenumber', true)

My question is, why is the option name not recognised by the buf_set_option function?

Answer 1

Kindly change vim.api.nvim_buf_set_option(0, 'relativenumber', true) to vim.wo.relativenumber = true, and same for other. It solves the issue.