[ES6 class syntax] lang-updated event listener is not called

[t2ym]

lang-updated event listener is not called on non-legacy ES6 class syntax

Workaround: Imperative listener addition at connectedCallback()

  connectedCallback() {
    super.connectedCallback();
    this.listen(this, 'lang-updated', '_langUpdated');
  }
  _langUpdated(effectiveLang) {
    this.model = deepcopy(this.text.model);
  }

Workaround 2: Use observers instead of listeners

• Be sure to handle the effectiveLang argument properly in the observer

    static config() {
      return {
        observers: [ '_langUpdated(effectiveLang)' ]
      }
    }
    _langUpdated(effectiveLang) {
      this.model = deepcopy(this.text.model);
    }

[t2ym]

Does this issue mean config.listeners is deprecated?

Polymer/polymer#4173