Run `next lint` via `lint-staged` in a monorepo

.lintstagedrc.js

import path from 'path'
import util from 'util'
import child_process from 'child_process'

const exec = util.promisify(child_process.exec)

const projectDirname = 'web' // Update with the path to your Next.js project

const buildEslintCommand = async (filenames) => {
  // `next lint` just silently ignores file inputs if the file doesn't exist,
  // and the default code snippet in the Next docs doesn't correctly construct
  // the file path if you're running `lint-staged` from a directory that's
  // outside the project root.
  const result = await exec('git rev-parse --show-toplevel')
  const gitRoot = result.stdout.trim()
  const projectDir = path.join(gitRoot, projectDirname)

  return `next lint --fix --file ${filenames
    .map((f) => path.relative(projectDir, f))
    .join(' --file ')}`
}

export default {
  '*.{js,ts,tsx}': [buildEslintCommand, 'prettier --write'],
  '*.!(js|ts|tsx)': 'prettier --write --ignore-unknown',
}