fix the order of calling reactions of fulfilled / rejected promises in Promise.prototype.then, close #1026

Author: zloirock

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Changelog
 ##### Unreleased
+- Fixed the order of calling reactions of fulfilled / rejected promises in `Promise.prototype.then`, [#1026](https://github.com/zloirock/core-js/issues/1026)
 - Fixed some missed dependencies of entries
 - Added Deno 1.18 compat data mapping
 

package.json

@@ -116,9 +116,9 @@
     "test-entries-content": "zx tests/commonjs-entries-content.mjs",
     "test-entries-standalone": "run-s init test-entries",
     "test-targets-parser": "zx tests/targets-parser.mjs",
-    "test": "run-s init test-lint bundle test-unit test-promises-aplus test-observables test-entries test-targets-parser check",
+    "test": "run-s init test-lint bundle test-unit test-promises test-observables test-entries test-targets-parser check",
     "ci-karma": "run-s init bundle test-unit-karma",
-    "ci-tests": "run-s init bundle test-unit-node test-promises-aplus test-observables test-entries test-targets-parser",
+    "ci-tests": "run-s init bundle test-unit-node test-promises test-observables test-entries test-targets-parser",
     "clean-dependencies": "node scripts/clean-dependencies.mjs",
     "refresh": "npm run clean-dependencies && npm it",
     "downloads": "zx scripts/downloads-by-versions.mjs",

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

@@ -4,6 +4,7 @@ var IS_PURE = require('../internals/is-pure');
 var global = require('../internals/global');
 var getBuiltIn = require('../internals/get-built-in');
 var call = require('../internals/function-call');
+var uncurryThis = require('../internals/function-uncurry-this');
 var NativePromise = require('../internals/native-promise-constructor');
 var redefine = require('../internals/redefine');
 var redefineAll = require('../internals/redefine-all');
@@ -43,6 +44,7 @@ var PromisePrototype = NativePromisePrototype;
 var TypeError = global.TypeError;
 var document = global.document;
 var process = global.process;
+var push = uncurryThis([].push);
 var newPromiseCapability = newPromiseCapabilityModule.f;
 var newGenericPromiseCapability = newPromiseCapability;
 
@@ -95,47 +97,50 @@ var isThenable = function (it) {
   return isObject(it) && isCallable(then = it.then) ? then : false;
 };
 
+var callReaction = function (reaction, state) {
+  var value = state.value;
+  var ok = state.state == FULFILLED;
+  var handler = ok ? reaction.ok : reaction.fail;
+  var resolve = reaction.resolve;
+  var reject = reaction.reject;
+  var domain = reaction.domain;
+  var result, then, exited;
+  try {
+    if (handler) {
+      if (!ok) {
+        if (state.rejection === UNHANDLED) onHandleUnhandled(state);
+        state.rejection = HANDLED;
+      }
+      if (handler === true) result = value;
+      else {
+        if (domain) domain.enter();
+        result = handler(value); // can throw
+        if (domain) {
+          domain.exit();
+          exited = true;
+        }
+      }
+      if (result === reaction.promise) {
+        reject(TypeError('Promise-chain cycle'));
+      } else if (then = isThenable(result)) {
+        call(then, result, resolve, reject);
+      } else resolve(result);
+    } else reject(value);
+  } catch (error) {
+    if (domain && !exited) domain.exit();
+    reject(error);
+  }
+};
+
 var notify = function (state, isReject) {
   if (state.notified) return;
   state.notified = true;
-  var chain = state.reactions;
   microtask(function () {
-    var value = state.value;
-    var ok = state.state == FULFILLED;
+    var chain = state.reactions;
     var index = 0;
     // variable length - can't use forEach
     while (chain.length > index) {
-      var reaction = chain[index++];
-      var handler = ok ? reaction.ok : reaction.fail;
-      var resolve = reaction.resolve;
-      var reject = reaction.reject;
-      var domain = reaction.domain;
-      var result, then, exited;
-      try {
-        if (handler) {
-          if (!ok) {
-            if (state.rejection === UNHANDLED) onHandleUnhandled(state);
-            state.rejection = HANDLED;
-          }
-          if (handler === true) result = value;
-          else {
-            if (domain) domain.enter();
-            result = handler(value); // can throw
-            if (domain) {
-              domain.exit();
-              exited = true;
-            }
-          }
-          if (result === reaction.promise) {
-            reject(TypeError('Promise-chain cycle'));
-          } else if (then = isThenable(result)) {
-            call(then, result, resolve, reject);
-          } else resolve(result);
-        } else reject(value);
-      } catch (error) {
-        if (domain && !exited) domain.exit();
-        reject(error);
-      }
+      callReaction(chain[index++], state);
     }
     state.reactions = [];
     state.notified = false;
@@ -265,14 +270,15 @@ if (FORCED) {
     // https://tc39.es/ecma262/#sec-promise.prototype.then
     then: function then(onFulfilled, onRejected) {
       var state = getInternalPromiseState(this);
-      var reactions = state.reactions;
       var reaction = newPromiseCapability(speciesConstructor(this, PromiseConstructor));
+      state.parent = true;
       reaction.ok = isCallable(onFulfilled) ? onFulfilled : true;
       reaction.fail = isCallable(onRejected) && onRejected;
       reaction.domain = IS_NODE ? process.domain : undefined;
-      state.parent = true;
-      reactions[reactions.length] = reaction;
-      if (state.state != PENDING) notify(state, false);
+      if (state.state == PENDING) push(state.reactions, reaction);
+      else microtask(function () {
+        callReaction(reaction, state);
+      });
       return reaction.promise;
     },
     // `Promise.prototype.catch` method