var global = require('../internals/global'); var NativePromiseConstructor = require('../internals/promise-native-constructor'); var isCallable = require('../internals/is-callable'); var isForced = require('../internals/is-forced'); var inspectSource = require('../internals/inspect-source'); var wellKnownSymbol = require('../internals/well-known-symbol'); var IS_BROWSER = require('../internals/engine-is-browser'); var IS_PURE = require('../internals/is-pure'); var V8_VERSION = require('../internals/engine-v8-version'); var NativePromisePrototype = NativePromiseConstructor && NativePromiseConstructor.prototype; var SPECIES = wellKnownSymbol('species'); var SUBCLASSING = false; var NATIVE_PROMISE_REJECTION_EVENT = isCallable(global.PromiseRejectionEvent); var FORCED_PROMISE_CONSTRUCTOR = isForced('Promise', function () { var PROMISE_CONSTRUCTOR_SOURCE = inspectSource(NativePromiseConstructor); var GLOBAL_CORE_JS_PROMISE = PROMISE_CONSTRUCTOR_SOURCE !== String(NativePromiseConstructor); // V8 6.6 (Node 10 and Chrome 66) have a bug with resolving custom thenables // https://bugs.chromium.org/p/chromium/issues/detail?id=830565 // We can't detect it synchronously, so just check versions if (!GLOBAL_CORE_JS_PROMISE && V8_VERSION === 66) return true; // We need Promise#{ catch, finally } in the pure version for preventing prototype pollution if (IS_PURE && !(NativePromisePrototype['catch'] && NativePromisePrototype['finally'])) return true; // We can't use @@species feature detection in V8 since it causes // deoptimization and performance degradation // https://github.com/zloirock/core-js/issues/679 if (V8_VERSION >= 51 && /native code/.test(PROMISE_CONSTRUCTOR_SOURCE)) return false; // Detect correctness of subclassing with @@species support var promise = new NativePromiseConstructor(function (resolve) { resolve(1); }); var FakePromise = function (exec) { exec(function () { /* empty */ }, function () { /* empty */ }); }; var constructor = promise.constructor = {}; constructor[SPECIES] = FakePromise; SUBCLASSING = promise.then(function () { /* empty */ }) instanceof FakePromise; if (!SUBCLASSING) return true; // Unhandled rejections tracking support, NodeJS Promise without it fails @@species test return !GLOBAL_CORE_JS_PROMISE && IS_BROWSER && !NATIVE_PROMISE_REJECTION_EVENT; }); module.exports = { CONSTRUCTOR: FORCED_PROMISE_CONSTRUCTOR, REJECTION_EVENT: NATIVE_PROMISE_REJECTION_EVENT, SUBCLASSING: SUBCLASSING };