How to extract filename of :w command in vim's autocmd?

Question

When I use Vim and type in the :w command, sometimes I will tap ] or \ by accident before I tap the Enter key because these keys are close to each other. As a result, I will get files such as ']' in my directory.

So I want to execute some autocmd in Vim to check if the file name which is going to be saved contains such special characters.

I have searched through the Internet, almost all of them give the solution of something like expand("%:p") to get file name. But after testing it by myself, this function can only obtain the current file name instead of the one I passed to :w command.

Is there any idea of obtaining the file name passed to :w command in Vim's autocmd?

Answer 1

I would propose you to introduce a command expression mapping cnoremap on the <CR> character. In the expression you could parse the command line and adapt it if it is wrong.

Here is a (too) simple example that detect ']' in your w[rite] leading command and replace it with \ waiting for your confirmation and do nothing otherwise.

function! CorrectWritePath()
  if getcmdtype() != ':'
    return "\<CR>"
  endif

  if matchstr(getcmdline(), '^w\%[rite]!\?\>') == ''
    return "\<CR>"
  endif

  let l:cmdline = getcmdline()

  " Parse the cmd line
  let l:newcmdline = l:cmdline
  let l:good = v:true
  if matchstr(l:cmdline, ']') != ''
    echo 'match'
    let l:newcmdline = substitute(l:cmdline, ']', '\', 'g')
    let l:good = v:false
  endif

  if l:good
    return "\<CR>"
  else
    return "\<C-u>" . l:newcmdline  
  endif

endfunction
cnoremap <expr> <CR> CorrectWritePath()