Save/load a quickfix list to a file

save_qf.vim

command! -nargs=1 -complete=file SaveQf call s:SaveQf(<f-args>)
command! -nargs=1 -complete=file LoadQf call s:LoadQf(<f-args>)

function! s:SaveQf(filename) abort
  let list = getqflist()

  for entry in list
    " Resolve each buffer to a filename, modify to take the absolute path
    let entry.filename = fnamemodify(bufname(entry.bufnr), ':p')
    " Remove bufnr to make sure Vim will deserialize the filename instead
    unlet entry.bufnr
  endfor

  let serialized_list = map(list, {_, entry -> json_encode(entry) })
  call writefile(serialized_list, a:filename)
endfunction

function! s:LoadQf(filename) abort
  if !filereadable(a:filename)
    echoerr "File not readable: " .. a:filename
    return
  endif

  let file_contents = readfile(a:filename)
  let quickfix_entries = map(file_contents, {_, line -> json_decode(line) })

  call setqflist(quickfix_entries)
  copen
endfunction