ale/ale_linters/javascript/eslint.vim

" Author: w0rp <devw0rp@gmail.com>
" Description: eslint for JavaScript files

let g:ale_javascript_eslint_executable =
\   get(g:, 'ale_javascript_eslint_executable', 'eslint')

let g:ale_javascript_eslint_options =
\   get(g:, 'ale_javascript_eslint_options', '')

let g:ale_javascript_eslint_use_global =
\   get(g:, 'ale_javascript_eslint_use_global', 0)

function! ale_linters#javascript#eslint#GetExecutable(buffer) abort
    if ale#Var(a:buffer, 'javascript_eslint_use_global')
        return ale#Var(a:buffer, 'javascript_eslint_executable')
    endif

    " Look for the kinds of paths that create-react-app generates first.
    let l:executable = ale#util#ResolveLocalPath(
    \   a:buffer,
    \   'node_modules/eslint/bin/eslint.js',
    \   ''
    \)

    if !empty(l:executable)
        return l:executable
    endif

    return ale#util#ResolveLocalPath(
    \   a:buffer,
    \   'node_modules/.bin/eslint',
    \   ale#Var(a:buffer, 'javascript_eslint_executable')
    \)
endfunction

function! ale_linters#javascript#eslint#GetCommand(buffer) abort
    return ale_linters#javascript#eslint#GetExecutable(a:buffer)
    \   . ' ' . ale#Var(a:buffer, 'javascript_eslint_options')
    \   . ' -f unix --stdin --stdin-filename %s'
endfunction

function! ale_linters#javascript#eslint#Handle(buffer, lines) abort
    let l:config_error_pattern = '\v^ESLint couldn''t find a configuration file'
    \   . '|^Cannot read config file'

    " Look for a message in the first few lines which indicates that
    " a configuration file couldn't be found.
    for l:line in a:lines[:10]
        if len(matchlist(l:line, l:config_error_pattern)) > 0
            return [{
            \   'lnum': 1,
            \   'text': 'eslint configuration error (type :ALEDetail for more information)',
            \   'detail': join(a:lines, "\n"),
            \}]
        endif
    endfor

    " Matches patterns line the following:
    "
    " /path/to/some-filename.js:47:14: Missing trailing comma. [Warning/comma-dangle]
    " /path/to/some-filename.js:56:41: Missing semicolon. [Error/semi]
    let l:pattern = '^.*:\(\d\+\):\(\d\+\): \(.\+\) \[\(.\+\)\]$'
    " This second pattern matches lines like the following:
    "
    " /path/to/some-filename.js:13:3: Parsing error: Unexpected token
    let l:parsing_pattern = '^.*:\(\d\+\):\(\d\+\): \(.\+\)$'
    let l:output = []

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

        if len(l:match) == 0
            " Try the parsing pattern for parsing errors.
            let l:match = matchlist(l:line, l:parsing_pattern)
        endif

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

        let l:type = 'Error'
        let l:text = l:match[3]

        " Take the error type from the output if available.
        if !empty(l:match[4])
            let l:type = split(l:match[4], '/')[0]
            let l:text .= ' [' . l:match[4] . ']'
        endif

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

    return l:output
endfunction

call ale#linter#Define('javascript', {
\   'name': 'eslint',
\   'executable_callback': 'ale_linters#javascript#eslint#GetExecutable',
\   'command_callback': 'ale_linters#javascript#eslint#GetCommand',
\   'callback': 'ale_linters#javascript#eslint#Handle',
\})