kibana/packages/kbn-utility-types/index.ts

/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you 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 { PromiseType } from 'utility-types';

/**
 * Returns wrapped type of a promise.
 */
export type UnwrapPromise<T extends Promise<any>> = PromiseType<T>;

/**
 * Minimal interface for an object resembling an `Observable`.
 */
export interface ObservableLike<T> {
  subscribe(observer: (value: T) => void): void;
}

/**
 * Returns wrapped type of an observable.
 */
export type UnwrapObservable<T extends ObservableLike<any>> = T extends ObservableLike<infer U>
  ? U
  : never;

/**
 * Converts a type to a `Promise`, unless it is already a `Promise`. Useful when proxying the return value of a possibly async function.
 */
export type ShallowPromise<T> = T extends Promise<infer U> ? Promise<U> : Promise<T>;