rsnext/packages/next/lib/recursive-copy.ts

import path from 'path'
import { promises, constants, Dirent, Stats } from 'fs'
import { Sema } from 'next/dist/compiled/async-sema'
import isError from './is-error'

const COPYFILE_EXCL = constants.COPYFILE_EXCL

export async function recursiveCopy(
  source: string,
  dest: string,
  {
    concurrency = 32,
    overwrite = false,
    filter = () => true,
  }: {
    concurrency?: number
    overwrite?: boolean
    filter?(filePath: string): boolean
  } = {}
): Promise<void> {
  const cwdPath = process.cwd()
  const from = path.resolve(cwdPath, source)
  const to = path.resolve(cwdPath, dest)

  const sema = new Sema(concurrency)

  // deep copy the file/directory
  async function _copy(item: string, lstats?: Stats | Dirent): Promise<void> {
    const target = item.replace(from, to)

    await sema.acquire()

    if (!lstats) {
      // after lock on first run
      lstats = await promises.lstat(from)
    }

    // readdir & lstat do not follow symbolic links
    // if part is a symbolic link, follow it with stat
    let isFile = lstats.isFile()
    let isDirectory = lstats.isDirectory()
    if (lstats.isSymbolicLink()) {
      const stats = await promises.stat(item)
      isFile = stats.isFile()
      isDirectory = stats.isDirectory()
    }

    if (isDirectory) {
      try {
        await promises.mkdir(target, { recursive: true })
      } catch (err) {
        // do not throw `folder already exists` errors
        if (isError(err) && err.code !== 'EEXIST') {
          throw err
        }
      }
      sema.release()
      const files = await promises.readdir(item, { withFileTypes: true })
      await Promise.all(
        files.map((file) => _copy(path.join(item, file.name), file))
      )
    } else if (
      isFile &&
      // before we send the path to filter
      // we remove the base path (from) and replace \ by / (windows)
      filter(item.replace(from, '').replace(/\\/g, '/'))
    ) {
      await promises.copyFile(
        item,
        target,
        overwrite ? undefined : COPYFILE_EXCL
      )
      sema.release()
    } else {
      sema.release()
    }
  }

  await _copy(from)
}