https://github.com/ryyppy/flow-vim-quickfix

flow-vim-quickfix.vim

if findfile('.flowconfig', '.;') !=# ''
  if executable($PWD .'/node_modules/.bin/flow')
    let g:flow_path = $PWD .'/node_modules/.bin/flow'
  else
    let g:flow_path = 'flow'
  endif

  let g:neomake_javascript_flow_maker = {
      \ 'exe': 'sh',
      \ 'args': ['-c', g:flow_path.' --json --strip-root | flow-vim-quickfix'],
      \ 'errorformat': '%E%f:%l:%c\,%n: %m',
      \ 'cwd': '%:p:h'
      \ }

  let g:neomake_javascript_enabled_makers = g:neomake_javascript_enabled_makers + [ 'flow']
endif