fix some cases of safe iteration closing

CHANGELOG.md

@@ -3,6 +3,7 @@
 - `AsyncFromSyncIterator` made stricter, related mainly to `AsyncIterator.from` and `AsyncIterator.prototype.flatMap`
 - Handling of optional `.next` arguments in `(Async)Iterator` methods is aligned with the current spec draft (mainly - ignoring the first passed to `.next` argument in built-in generators)
 - Behavior of `.next`, `.return`, `.throw` methods on `AsyncIterator` helpers proxy iterators aligned with the current spec draft (built-in async generators) (mainly - some early errors moved to returned promises)
+- Fixed some cases of safe iteration closing
 
 ##### 3.16.3 - 2021.08.25
 - Fixed `CreateAsyncFromSyncIterator` semantic in `AsyncIterator.from`, related to [#765](https://github.com/zloirock/core-js/issues/765)

packages/core-js/internals/call-with-safe-iteration-closing.js

@@ -6,7 +6,6 @@ module.exports = function (iterator, fn, value, ENTRIES) {
   try {
     return ENTRIES ? fn(anObject(value)[0], value[1]) : fn(value);
   } catch (error) {
-    iteratorClose(iterator);
-    throw error;
+    iteratorClose(iterator, 'throw', error);
   }
 };

packages/core-js/internals/iterate.js

@@ -20,7 +20,7 @@ module.exports = function (iterable, unboundFunction, options) {
   var iterator, iterFn, index, length, result, next, step;
 
   var stop = function (condition) {
-    if (iterator) iteratorClose(iterator);
+    if (iterator) iteratorClose(iterator, 'return', condition);
     return new Result(true, condition);
   };
 
@@ -51,8 +51,7 @@ module.exports = function (iterable, unboundFunction, options) {
     try {
       result = callFn(step.value);
     } catch (error) {
-      iteratorClose(iterator);
-      throw error;
+      iteratorClose(iterator, 'throw', error);
     }
     if (typeof result == 'object' && result && result instanceof Result) return result;
   } return new Result(false);

packages/core-js/internals/iterator-close.js

@@ -1,8 +1,21 @@
 var anObject = require('../internals/an-object');
 
-module.exports = function (iterator) {
-  var returnMethod = iterator['return'];
-  if (returnMethod !== undefined) {
-    return anObject(returnMethod.call(iterator)).value;
+module.exports = function (iterator, kind, value) {
+  var innerResult, innerError;
+  anObject(iterator);
+  try {
+    innerResult = iterator['return'];
+    if (innerResult === undefined) {
+      if (kind === 'throw') throw value;
+      return value;
+    }
+    innerResult = innerResult.call(iterator);
+  } catch (error) {
+    innerError = true;
+    innerResult = error;
   }
+  if (kind === 'throw') throw value;
+  if (innerError) throw innerResult;
+  anObject(innerResult);
+  return value;
 };

packages/core-js/modules/esnext.iterator.flat-map.js

@@ -34,8 +34,7 @@ var IteratorProxy = createIteratorProxy(function () {
       this.innerIterator = innerIterator = anObject(iteratorMethod.call(mapped));
       this.innerNext = aFunction(innerIterator.next);
     } catch (error) {
-      iteratorClose(iterator);
-      throw error;
+      iteratorClose(iterator, 'throw', error);
     }
   }
 });

packages/core-js/modules/esnext.iterator.take.js

@@ -10,7 +10,7 @@ var IteratorProxy = createIteratorProxy(function (args) {
   var iterator = this.iterator;
   if (!this.remaining--) {
     this.done = true;
-    return iteratorClose(iterator);
+    return iteratorClose(iterator, 'return', undefined);
   }
   var result = anObject(this.next.apply(iterator, args));
   var done = this.done = !!result.done;