don't wrap Promise#then of incorrect native Promise implementatio…

…ns with correct subclassing
zloirock · May 3, 2021 · e280a0a · e280a0a
1 parent c78f69d
commit e280a0a
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## Changelog
 ##### Unreleased
 - Added a workaround of WebKit ~ iOS 10.3 Safari `Promise` instantiation bug, [#932](https://github.com/zloirock/core-js/issues/932)
+- `Promise#then` of incorrect native `Promise` implementations with correct subclassing no longer wrapped
 
 ##### 3.11.1 - 2021.04.28
 - Made `instanceof Promise` and `.constructor === Promise` work with polyfilled `Promise` for all native promise-based APIs

diff --git a/packages/core-js/modules/es.promise.js b/packages/core-js/modules/es.promise.js
@@ -49,6 +49,7 @@ var FULFILLED = 1;
 var REJECTED = 2;
 var HANDLED = 1;
 var UNHANDLED = 2;
+var SUBCLASSING = false;
 var Internal, OwnPromiseCapability, PromiseWrapper, nativeThen;
 
 var FORCED = isForced(PROMISE, function () {
@@ -74,7 +75,7 @@ var FORCED = isForced(PROMISE, function () {
   };
   var constructor = promise.constructor = {};
   constructor[SPECIES] = FakePromise;
-  return !(promise.then(function () { /* empty */ }) instanceof FakePromise);
+  return !(SUBCLASSING = promise.then(function () { /* empty */ }) instanceof FakePromise);
 });
 
 var INCORRECT_ITERATION = FORCED || !checkCorrectnessOfIteration(function (iterable) {
@@ -288,7 +289,7 @@ if (FORCED) {
     nativeThen = NativePromisePrototype.then;
 
     // make `Promise#then` return a polyfilled `Promise` for native promise-based APIs
-    redefine(NativePromisePrototype, 'then', function then(onFulfilled, onRejected) {
+    if (!SUBCLASSING) redefine(NativePromisePrototype, 'then', function then(onFulfilled, onRejected) {
       var that = this;
       return new PromiseConstructor(function (resolve, reject) {
         nativeThen.call(that, resolve, reject);