// size does not match its declared size).
//
// dir may or may not exist: Unzip will create it and any missing parent
// directories if it doesn't exist. If dir exists, it must be empty.
func Unzip(dir string, m module.Version, zipFile string) (err error) {
	defer func() {
		if err != nil {
			err = &zipError{verb: "unzip", path: zipFile, err: err}
		}
	}()

	if err != nil {
		return "", err
	}

	unlock, err := lockVersion(ctx, mod)
	if err != nil {
		return "", err
	}
	defer unlock()

	ctx, span = trace.StartSpan(ctx, "unzip "+zipfile)
	defer span.Done()

	// Check whether the directory was populated while we were waiting on the lock.
	_, dirErr := DownloadDir(ctx, mod)
	if dirErr == nil {
		return dir, nil
	}