@vue/cli-plugin-eslint/index.js

const path = require('path')

module.exports = (api, options) => {
  if (options.lintOnSave) {
    const extensions = require('./eslintOptions').extensions(api)
    // Use loadModule to allow users to customize their ESLint dependency version.
    const { resolveModule, loadModule } = require('@vue/cli-shared-utils')
    const cwd = api.getCwd()
    const eslintPkg =
      loadModule('eslint/package.json', cwd, true) ||
      loadModule('eslint/package.json', __dirname, true)

    // eslint-loader doesn't bust cache when eslint config changes
    // so we have to manually generate a cache identifier that takes the config
    // into account.
    const { cacheIdentifier } = api.genCacheConfig(
      'eslint-loader',
      {
        'eslint-loader': require('eslint-loader/package.json').version,
        eslint: eslintPkg.version
      },
      [
        '.eslintrc.js',
        '.eslintrc.yaml',
        '.eslintrc.yml',
        '.eslintrc.json',
        '.eslintrc',
        '.eslintignore',
        'package.json'
      ]
    )

    api.chainWebpack(webpackConfig => {
      const { lintOnSave } = options
      const allWarnings = lintOnSave === true || lintOnSave === 'warning'
      const allErrors = lintOnSave === 'error'

      webpackConfig.module
        .rule('eslint')
          .pre()
          .exclude
            .add(/node_modules/)
            .add(path.dirname(require.resolve('@vue/cli-service')))
            .end()
          .test(/\.(vue|(j|t)sx?)$/)
          .use('eslint-loader')
            .loader(require.resolve('eslint-loader'))
            .options({
              extensions,
              cache: true,
              cacheIdentifier,
              emitWarning: allWarnings,
              // only emit errors in production mode.
              emitError: allErrors,
              eslintPath: path.dirname(
                resolveModule('eslint/package.json', cwd) ||
                resolveModule('eslint/package.json', __dirname)
              ),
              formatter: loadModule('eslint/lib/formatters/codeframe', cwd, true)
            })
    })
  }

  api.registerCommand(
    'lint',
    {
      description: 'lint and fix source files',
      usage: 'vue-cli-service lint [options] [...files]',
      options: {
        '--format [formatter]': 'specify formatter (default: codeframe)',
        '--no-fix': 'do not fix errors or warnings',
        '--no-fix-warnings': 'fix errors, but do not fix warnings',
        '--max-errors [limit]':
          'specify number of errors to make build failed (default: 0)',
        '--max-warnings [limit]':
          'specify number of warnings to make build failed (default: Infinity)'
      },
      details:
        'For more options, see https://eslint.org/docs/user-guide/command-line-interface#options'
    },
    args => {
      require('./lint')(args, api)
    }
  )
}