def run(self, edit):
    vsize = self.view.size()
    region = sublime.Region(0, vsize)
    src = self.view.substr(region)
    window = self.view.window()

    settings = sublime.load_settings('Crystal.sublime-settings')
    startupinfo = subprocess.STARTUPINFO()
    startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
    pipe = open(os.devnull, 'w')
    # Prevent flashing windows if used from a GUI application
    startupinfo = subprocess.STARTUPINFO()
    startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
    proc = [settings.get("crystal_cmd"), "tool", "format", "-", "--format", "json"]
    rc = subprocess.call([settings.get("crystal_cmd"), "tool", "format", "-", "--format", "json"], stdout = pipe, stderr = pipe,startupinfo = startupinfo)
    proc.stdin.write(bytes(src, 'UTF-8'))
    proc.stdin.close()
    output = proc.stdout.read().decode('UTF-8')
    exit = proc.wait()
    pos = 0

    return self.run(edit)
  File "crystal_format in C:\Users\Administrator\AppData\Roaming\Sublime Text 3\Installed Packages\Crystal.sublime-package", line 38, in run
AttributeError: __exit__

  def run(self, edit):
    vsize = self.view.size()
    region = sublime.Region(0, vsize)
    src = self.view.substr(region)
    window = self.view.window()

    settings = sublime.load_settings('Crystal.sublime-settings')
    command = [settings.get("crystal_cmd"), "tool", "format", "-", "--format", "json"]

    popen_args = dict(args=command, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
    # Prevent flashing terminal windows
    if sys.platform.startswith('win'):
      popen_args['startupinfo'] = subprocess.STARTUPINFO()
      popen_args['startupinfo'].dwFlags |= subprocess.STARTF_USESHOWWINDOW

    with subprocess.Popen(**popen_args) as proc:
      output, _ = proc.communicate(src.encode('utf-8'))
      output = output.decode('utf-8')

    pos = 0
    if not self.has_redo():
      for op, text in diff_match_patch().diff_main(src, output):
        if op == diff_match_patch.DIFF_DELETE:
          self.view.erase(edit, sublime.Region(pos, pos + len(text)))
        if op == diff_match_patch.DIFF_INSERT:
          self.view.insert(edit, pos, text)
          pos += len(text)
        if op == diff_match_patch.DIFF_EQUAL:
          pos += len(text)

      self.view.erase_regions('crystal_errors')
      window.run_command("hide_panel")

    else:
      error = json.loads(output)
      error_pos = self.view.text_point(error[0]["line"] - 1, error[0]["column"] - 1)
      line_region = self.view.full_line(error_pos)
      self.view.add_regions('crystal_errors', [line_region], 'comment', 'dot', sublime.HIDDEN)

      error_panel = window.create_output_panel('crystal_errors')
      error_panel.run_command("append", {"characters":
        "Error at line %d, column %d: %s" % (error[0]["line"], error[0]["column"], error[0]['message'])
      })
      window.run_command("show_panel", {"panel": "output.crystal_errors"})