Creating and destroying temporary files by vim

Question

I integrated luacheck in vim with the following simple function:

function! LuaCheck()
  let errors=system("luacheck " . expand("%"))
  cexpr errors
  cwindow 5
endfunction
autocmd FileType lua nnoremap <buffer> <c-f> :call LuaCheck()<cr>
autocmd FileType lua set efm=%f:%l:%c:\ %m

It is working, but here is a problem: luacheck doesn't have interactive mode, it works only with files. So I have to use expand("%") instead of getline(1, "$"). When I changed something in buffer I need to save it before checking - it is bad practice. I want to create a temporary file, save content of buffer to it, check temporary file and remove it. But I don't know how to create the temporary file in vimscript. Is this possible? Or I need use external tools for it?

Answer 1

You can create temporary file name with :h tempname():

let tempname = tempname()
call writefile([ "hello world" ], tempname)
" do something with tempname file
" ...
call delete(tempname)

Answer 2

There are different approaches to this problem. Assuming your Vim has('job') you can do:

let temp = bufadd('noname')
call setbufvar(temp, '&buftype', 'nofile')
call bufload(temp)
let job = job_start('luacheck', #{in_io: 'buffer', in_buf: bufnr(),
    \ out_io: 'buffer', out_buf: temp,
    \ exit_cb: {id, status -> execute(printf('cb %d | bw %d | cw 5', temp, temp))}
    \ })