add detection of missed Webkit ~ Safari < 26.2 Iterator.prototype.flatMap bug case, close #1538

CHANGELOG.md

@@ -25,6 +25,7 @@
     - `Promise.allSettledKeyed`
 - Throw a `RangeError` on finite unsafe integer `limit` in `Iterator.prototype.{ drop, take }`, following [tc39/ecma262/#3776](https://github.com/tc39/ecma262/pull/3776)
 - Use `PromiseResolve` semantics in `Promise.try`, following [tc39/ecma262/#3883](https://github.com/tc39/ecma262/pull/3883)
+- Added detection of missed [Webkit ~ Safari < 26.2 `Iterator.prototype.flatMap` bug](https://bugs.webkit.org/show_bug.cgi?id=297532) case, [#1538](https://github.com/zloirock/core-js/issues/1538)
 - Deno 2.9+ [*replaces* `Object.prototype.__proto__`](https://github.com/denoland/deno/pull/35192) instead of removing it, so the feature detection updated
 - Ensure opaque paths always roundtrip in URL polyfill (still without adding to feature detection), [whatwg/url#844](https://github.com/whatwg/url/pull/844)
 - Fixed possible crash on some keys in `Symbol.for`
@@ -34,7 +35,7 @@
 - Improved the way of inner iterators cleaning in iterator helpers
 - Improved accuracy of `Math.{ asinh, cbrt, log1p }` polyfills with big and small values
 - Improved performance of `Uint8Array` base64 methods
-- Improved performance of `es.escape`
+- Improved performance of `escape`
 - Slight performance improvement for engines with native `Array#fill` on `ArrayBuffer` constructor and `%TypedArray%#fill`
 - Clarify supported Node versions in `package.json` of some missed packages (just to satisfy `publint`)
 - Compat data improvements:

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

@@ -15,10 +15,11 @@ var iteratorHelperWithoutClosingOnEarlyError = require('../internals/iterator-he
 // https://bugs.webkit.org/show_bug.cgi?id=297532
 function throwsOnIteratorWithoutReturn() {
   try {
-    // eslint-disable-next-line es/no-map, es/no-iterator, es/no-iterator-prototype-flatmap -- required for testing
-    var it = Iterator.prototype.flatMap.call(new Map([[4, 5]]).entries(), function (v) { return v; });
-    it.next();
-    it['return']();
+    // eslint-disable-next-line es/no-array-prototype-values, es/no-iterator-prototype-flatmap, es/no-iterator-prototype-find -- testing
+    [1].values()
+      .flatMap(function () { return [1]; })
+      .find(function () { return true; });
+    return false;
   } catch (error) {
     return true;
   }
@@ -26,6 +27,7 @@ function throwsOnIteratorWithoutReturn() {
 
 var FLAT_MAP_WITHOUT_THROWING_ON_INVALID_ITERATOR = !IS_PURE
   && !iteratorHelperThrowsOnInvalidIterator('flatMap', function () { /* empty */ });
+
 var flatMapWithoutClosingOnEarlyError = !IS_PURE && !FLAT_MAP_WITHOUT_THROWING_ON_INVALID_ITERATOR
   && iteratorHelperWithoutClosingOnEarlyError('flatMap', TypeError);
 

tests/unit-global/es.iterator.flat-map.js

@@ -31,6 +31,8 @@ QUnit.test('Iterator#flatMap', assert => {
     iter.return();
   }, 'iterator without `return` method');
 
+  assert.same([1].values().flatMap(() => [1]).find(() => true), 1, 'iterator without `return` method #2');
+
   if (STRICT) {
     assert.throws(() => flatMap.call(undefined, () => { /* empty */ }), TypeError);
     assert.throws(() => flatMap.call(null, () => { /* empty */ }), TypeError);

tests/unit-pure/es.iterator.flat-map.js

@@ -3,9 +3,10 @@ import { STRICT, STRICT_THIS } from '../helpers/constants.js';
 
 import Iterator from 'core-js-pure/es/iterator';
 import Map from 'core-js-pure/es/map';
+import values from 'core-js-pure/es/array/values';
 
 QUnit.test('Iterator#flatMap', assert => {
-  const { flatMap } = Iterator.prototype;
+  const { flatMap, find } = Iterator.prototype;
 
   assert.isFunction(flatMap);
   assert.arity(flatMap, 1);
@@ -33,6 +34,8 @@ QUnit.test('Iterator#flatMap', assert => {
     iter.return();
   }, 'iterator without `return` method');
 
+  assert.same(find.call(flatMap.call(values([1]), () => [1]), () => true), 1, 'iterator without `return` method #2');
+
   if (STRICT) {
     assert.throws(() => flatMap.call(undefined, () => { /* empty */ }), TypeError);
     assert.throws(() => flatMap.call(null, () => { /* empty */ }), TypeError);