I am trying to write a function to lint buffers in neovim. It seems that the usual recommendation for achieving such a thing is to run the command over the entire range (ie %!lint). This is however, problematic if the file is not properly formatted. In (neo)vim's current behaviour, it appears that even stderr output from the lint program will replace the entire buffer.

I have attempted to fix this by running the lint command separately and checking for shell errors, like so:

" example usage:
" :call RunBuf("python -m json.tool")
function! RunBuf(cmd) abort
  redir => output
  silent execute ":w !" . a:cmd
  redir END
  if v:shell_error
    echo output
  let pos = getcurpos()
  execute "%!" . a:cmd
  call setpos('.', pos)

This is still not optimal as the lint command needs to be executed twice. I am thinking if there is a way to replace the entire buffer with output, or if there's a simpler way of achieving the same?


One option would be to

  • run the linter on the file and shove the output in a temporary file (relevant docs: :range!, :make, shell, shellredir, shellcmdflag, shellpipe, tempname())
  • if no error, simply replace everything with that file: :%delete | execute 'read' tempfile | 0delete
  • delete the tempfile (:call delete(tempfile))

I think this would look like (but I haven't tested it yet):

function RunBuf(cmd) abort
  let temp = tempname()
  silent execute 'write !' cmd &shellredir temp
  if v:shell_error is# 0
    execute '1read' temp
  call delete(temp)

However, you might be better off integrating with something like ALE (which, AFAIK, handles all this nonsense for you) or another linter plugin.

I think the reason stderr is usually included is because shellpipe and shellredir are set to include stderr when the shell supports it.

  • 2
    Note that this is most of what :range! does, just with the extra error checking – D. Ben Knoble Aug 20 '20 at 21:16

D Ben Knoble's answer looks promising, but I hated the idea of using temporary files. After some digging, I found another way to achieve the desired behaviour, largely stolen from the dart vim plugin fmt iimplementation:

function! RunBuf(cmd) abort
  let buffer_content = getline(1, '$')
  let lines = systemlist(a:cmd, join(buffer_content, "\n"))
  if v:shell_error
    echo join(lines, "\n")
  silent keepjumps call setline(1, lines)
  if line('$') > len(lines)
    silent keepjumps execute string(len(lines)+1).',$ delete'

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