core-js/modules/es.promise.finally.js

'use strict';
var $ = require('../internals/export');
var IS_PURE = require('../internals/is-pure');
var NativePromiseConstructor = require('../internals/promise-native-constructor');
var fails = require('../internals/fails');
var getBuiltIn = require('../internals/get-built-in');
var isCallable = require('../internals/is-callable');
var speciesConstructor = require('../internals/species-constructor');
var promiseResolve = require('../internals/promise-resolve');
var defineBuiltIn = require('../internals/define-built-in');

var NativePromisePrototype = NativePromiseConstructor && NativePromiseConstructor.prototype;

// Safari bug https://bugs.webkit.org/show_bug.cgi?id=200829
var NON_GENERIC = !!NativePromiseConstructor && fails(function () {
  // eslint-disable-next-line unicorn/no-thenable -- required for testing
  NativePromisePrototype['finally'].call({ then: function () { /* empty */ } }, function () { /* empty */ });
});

// `Promise.prototype.finally` method
// https://tc39.es/ecma262/#sec-promise.prototype.finally
$({ target: 'Promise', proto: true, real: true, forced: NON_GENERIC }, {
  'finally': function (onFinally) {
    var C = speciesConstructor(this, getBuiltIn('Promise'));
    var isFunction = isCallable(onFinally);
    return this.then(
      isFunction ? function (x) {
        return promiseResolve(C, onFinally()).then(function () { return x; });
      } : onFinally,
      isFunction ? function (e) {
        return promiseResolve(C, onFinally()).then(function () { throw e; });
      } : onFinally
    );
  }
});

// makes sure that native promise-based APIs `Promise#finally` properly works with patched `Promise#then`
if (!IS_PURE && isCallable(NativePromiseConstructor)) {
  var method = getBuiltIn('Promise').prototype['finally'];
  if (NativePromisePrototype['finally'] !== method) {
    defineBuiltIn(NativePromisePrototype, 'finally', method, { unsafe: true });
  }
}