polygerrit-ui/app/elements/plugins/gr-endpoint-param/gr-endpoint-param.js

/**
 * @license
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import '../../../scripts/bundled-polymer.js';

import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
import {PolymerElement} from '@polymer/polymer/polymer-element.js';

/** @extends Polymer.Element */
class GrEndpointParam extends GestureEventListeners(
    LegacyElementMixin(
        PolymerElement)) {
  static get is() { return 'gr-endpoint-param'; }

  static get properties() {
    return {
      name: String,
      value: {
        type: Object,
        notify: true,
        observer: '_valueChanged',
      },
    };
  }

  _valueChanged(newValue, oldValue) {
    /* In polymer 2 the following change was made:
    "Property change notifications (property-changed events) aren't fired when
    the value changes as a result of a binding from the host"
    (see https://polymer-library.polymer-project.org/2.0/docs/about_20).
    To workaround this problem, we fire the event from the observer.
    In some cases this fire the event twice, but our code is
    ready for it.
    */
    const detail = {
      value: newValue,
    };
    this.dispatchEvent(new CustomEvent('value-changed', {detail}));
  }
}

customElements.define(GrEndpointParam.is, GrEndpointParam);