fix a modern Safari bug in Array.prototype.includes with sparse arrays and fromIndex

https://bugs.webkit.org/show_bug.cgi?id=309342

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Minor performance optimization polyfills of methods from [`Map` upsert proposal](https://github.com/tc39/proposal-upsert)
 - Polyfills of methods from [`Map` upsert proposal](https://github.com/tc39/proposal-upsert) from the pure version made generic to make it work with polyfilled and native collections
 - Wrap `Symbol.for` in `Symbol.prototype.description` polyfill for correct handling of empty string descriptions
+- Fixed [a modern Safari bug](https://bugs.webkit.org/show_bug.cgi?id=309342) in `Array.prototype.includes` with sparse arrays and `fromIndex`
 - Fixed one more case (`Iterator.prototype.take`) of a V8 ~ Chromium < 126 [bug](https://issues.chromium.org/issues/336839115)
 - Forced replacement of `Iterator.{ concat, zip, zipKeyed }` in the pure version for ensuring proper wrapped `Iterator` instances as the result
 - Fixed proxying `.return()` on exhausted iterator from some methods of iterator helpers polyfill to the underlying iterator
@@ -97,6 +98,7 @@
   - [`Math.sumPrecise`](https://github.com/tc39/proposal-math-sum) marked as [shipped in V8 ~ Chrome 147](https://issues.chromium.org/issues/374310075#comment16)
   - [`Iterator.concat`](https://github.com/tc39/proposal-iterator-sequencing) marked as [shipped in V8 ~ Chrome 146](https://issues.chromium.org/issues/434977727#comment7)
   - [`Iterator.concat`](https://github.com/tc39/proposal-iterator-sequencing) marked as shipped in Safari 26.4
+  - Because of [a bug](https://bugs.webkit.org/show_bug.cgi?id=309342), `Array.prototype.includes` marked as not supported in modern Safari
   - Fixed compat data for `parseInt` and `parseFloat`
   - Added Deno [2.6.7](https://github.com/denoland/deno/releases/tag/v2.6.7), [2.7.0](https://github.com/denoland/deno/releases/tag/v2.7.0) and [2.7.2](https://github.com/denoland/deno/releases/tag/v2.7.2) compat data mapping
   - Added Electron 42 compat data mapping

packages/core-js-compat/src/data.mjs

@@ -314,7 +314,9 @@ export const data = {
     // FF99-101 broken on sparse arrays
     firefox: '102', // '48',
     rhino: '1.8.0',
-    safari: '10.0',
+    // Safari broken on sparse arrays with fromIndex
+    // https://bugs.webkit.org/show_bug.cgi?id=309342
+    // safari: '10.0',
   },
   'es.array.index-of': {
     chrome: '51',

packages/core-js/modules/es.array.includes.js

@@ -10,9 +10,15 @@ var BROKEN_ON_SPARSE = fails(function () {
   return !Array(1).includes();
 });
 
+// Safari 26.4- bug
+var BROKEN_ON_SPARSE_WITH_FROM_INDEX = fails(function () {
+  // eslint-disable-next-line no-sparse-arrays, es/no-array-prototype-includes -- detection
+  return [, 1].includes(undefined, 1);
+});
+
 // `Array.prototype.includes` method
 // https://tc39.es/ecma262/#sec-array.prototype.includes
-$({ target: 'Array', proto: true, forced: BROKEN_ON_SPARSE }, {
+$({ target: 'Array', proto: true, forced: BROKEN_ON_SPARSE || BROKEN_ON_SPARSE_WITH_FROM_INDEX }, {
   includes: function includes(el /* , fromIndex = 0 */) {
     return $includes(this, el, arguments.length > 1 ? arguments[1] : undefined);
   }

tests/compat/tests.js

@@ -526,7 +526,10 @@ GLOBAL.tests = {
   'es.array.from': SAFE_ITERATION_CLOSING_SUPPORT,
   'es.array.includes': function () {
     return Array(1).includes()
-      && Array.prototype[Symbol.unscopables].includes;
+      && Array.prototype[Symbol.unscopables].includes
+      // https://bugs.webkit.org/show_bug.cgi?id=309342
+      // eslint-disable-next-line no-sparse-arrays -- testing
+      && ![, 1].includes(undefined, 1);
   },
   'es.array.index-of': function () {
     try {

tests/unit-global/es.array.includes.js

@@ -18,6 +18,9 @@ QUnit.test('Array#includes', assert => {
   assert.false(array.includes({}));
   assert.true(Array(1).includes(undefined));
   assert.true([NaN].includes(NaN));
+  // https://bugs.webkit.org/show_bug.cgi?id=309342
+  // eslint-disable-next-line no-sparse-arrays -- testing
+  assert.false([, 1].includes(undefined, 1), '`Array#includes(undefined, fromIndex)` should not find holes before fromIndex');
   if (STRICT) {
     assert.throws(() => includes.call(null, 0), TypeError);
     assert.throws(() => includes.call(undefined, 0), TypeError);

tests/unit-pure/es.array.includes.js

@@ -15,6 +15,9 @@ QUnit.test('Array#includes', assert => {
   assert.false(includes(array, {}));
   assert.true(includes(Array(1), undefined));
   assert.true(includes([NaN], NaN));
+  // https://bugs.webkit.org/show_bug.cgi?id=309342
+  // eslint-disable-next-line no-sparse-arrays -- testing
+  assert.false(includes([, 1], undefined, 1), '`Array#includes(undefined, fromIndex)` should not find holes before fromIndex');
   if (STRICT) {
     assert.throws(() => includes(null, 0), TypeError);
     assert.throws(() => includes(undefined, 0), TypeError);