ale/ale_linters/ruby/rubocop.vim

" Author: ynonp - https://github.com/ynonp
" Description: rubocop for Ruby files

function! ale_linters#ruby#rubocop#Handle(buffer, lines) abort
    " Matches patterns line the following:
    "
    " <path>:83:29: C: Prefer single-quoted strings when you don't
    " need string interpolation or special symbols.
    let l:pattern = '\v:(\d+):(\d+): (.): (.+)'
    let l:output = []

    for l:line in a:lines
        let l:match = matchlist(l:line, l:pattern)

        if len(l:match) == 0
            continue
        endif

        let l:text = l:match[4]
        let l:type = l:match[3]

        call add(l:output, {
        \   'bufnr': a:buffer,
        \   'lnum': l:match[1] + 0,
        \   'col': l:match[2] + 0,
        \   'text': l:text,
        \   'type': index(['F', 'E'], l:type) != -1 ? 'E' : 'W',
        \})
    endfor

    return l:output
endfunction

function! ale_linters#ruby#rubocop#GetCommand(buffer) abort
    return 'rubocop --format emacs --force-exclusion '
    \   . ale#Var(a:buffer, 'ruby_rubocop_options')
    \   . ' --stdin ' . bufname(a:buffer)
endfunction

" Set this option to change Rubocop options.
if !exists('g:ale_ruby_rubocop_options')
    " let g:ale_ruby_rubocop_options = '--lint'
    let g:ale_ruby_rubocop_options = ''
endif

call ale#linter#Define('ruby', {
\   'name': 'rubocop',
\   'executable': 'rubocop',
\   'command_callback': 'ale_linters#ruby#rubocop#GetCommand',
\   'callback': 'ale_linters#ruby#rubocop#Handle',
\})