@jsenv/util/src/ensureWindowsDriveLetter.js

Set of functions often needed when using Node.js.

import { fileSystemPathToUrl } from "./fileSystemPathToUrl.js"

const isWindows = process.platform === "win32"
const baseUrlFallback = fileSystemPathToUrl(process.cwd())

/**
 * Some url might be resolved or remapped to url without the windows drive letter.
 * For instance
 * new URL('/foo.js', 'file:///C:/dir/file.js')
 * resolves to
 * 'file:///foo.js'
 *
 * But on windows it becomes a problem because we need the drive letter otherwise
 * url cannot be converted to a filesystem path.
 *
 * ensureWindowsDriveLetter ensure a resolved url still contains the drive letter.
 */

export const ensureWindowsDriveLetter = (url, baseUrl) => {
  try {
    url = String(new URL(url))
  } catch (e) {
    throw new Error(`absolute url expected but got ${url}`)
  }

  if (!isWindows) {
    return url
  }

  try {
    baseUrl = String(new URL(baseUrl))
  } catch (e) {
    throw new Error(
      `absolute baseUrl expected but got ${baseUrl} to ensure windows drive letter on ${url}`,
    )
  }

  if (!url.startsWith("file://")) {
    return url
  }
  const afterProtocol = url.slice("file://".length)
  // we still have the windows drive letter
  if (extractDriveLetter(afterProtocol)) {
    return url
  }

  // drive letter was lost, restore it
  const baseUrlOrFallback = baseUrl.startsWith("file://") ? baseUrl : baseUrlFallback
  const driveLetter = extractDriveLetter(baseUrlOrFallback.slice("file://".length))
  if (!driveLetter) {
    throw new Error(
      `drive letter expected on baseUrl but got ${baseUrl} to ensure windows drive letter on ${url}`,
    )
  }
  return `file:///${driveLetter}:${afterProtocol}`
}

const extractDriveLetter = (ressource) => {
  // we still have the windows drive letter
  if (/[a-zA-Z]/.test(ressource[1]) && ressource[2] === ":") {
    return ressource[1]
  }
  return null
}