text: /**
   * Copyright 2020 The AMP HTML Authors. All Rights Reserved.
   *
   * 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 {devAssert} from '../core/assert';
  
  const EMPTY_DEPS = [];
  
  /**
   * Creates the `ContextProp` type.
   *
   * @param {string} key
   * @param {{
   *   type: (!Object|undefined),
   *   deps: (!Array<!ContextProp>|undefined),
   *   recursive: (boolean|(function(!Array<T>):boolean)|undefined),
   *   compute: ((function(!Node, !Array<T>, ...*):(T|undefined))|undefined),
   *   defaultValue: (T|undefined),
   * }=} opt_spec
   * @return {!ContextProp<T>}
   * @template T
   */
  export function contextProp(key, opt_spec) {
    const prop = /** @type {!ContextProp<T>} */ ({
      key,
      // Default values.
      type: null,
      deps: EMPTY_DEPS,
      recursive: false,
      compute: null,
      defaultValue: undefined,
      // Overrides.
      ...opt_spec,
    });
    devAssert(prop.deps.length == 0 || prop.compute);
    return prop;
  }
  