198643 2019-06-06 21:29:07 -0700 async function resolution order 2023-10-11 17:03:24 -0700 1 1 1 Unclassified WebKit JavaScriptCore Safari 12 Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 johnplaisted webkit-unassigned ashvayka fpizlo keith_miller mark.lam webkit-bug-importer ysuzuki oldest_to_newest 1542713 0 371556 johnplaisted 2019-06-06 21:29:07 -0700 Created attachment 371556 Test demonstrating differences in async / promise behavior Steps to reproduce: The await keyword has a different resolution order than Promises, which seems incorrect (and fwiw Chrome's await matches promises; FireFox appears to share Safari's behavior). I think I've found two different cases where the order is different from promises: In some cases the await order determines when functions continue (rather than the resolve() order, assuming things resolve synchronously) In some other cases it seems to be the opposite of the resolve AND await order when the are the same order. Maybe it is because one is an await <literal> and the other is an await promise? Actual results: The order of asynchronous code with an async function doesn't match the equivalent promise code. When running the file: async test fails promise test passes order of await determines order of async callbacks order resolve() determines order of promise callbacks Expected results: The async function order matches the Promise equivalent. When running the file: async test passes promise test passes order of resolve() determines order of async callbacks order resolve() determines order of promise callbacks 1542826 1 johnplaisted 2019-06-07 08:12:14 -0700 I did file a webkit bug as well: https://bugs.webkit.org/show_bug.cgi?id=198643 1542827 2 johnplaisted 2019-06-07 08:12:45 -0700 Err, I filed a *FireFox* bug as well :) https://bugzilla.mozilla.org/show_bug.cgi?id=1557611 1971196 3 webkit-bug-importer 2023-08-14 18:32:37 -0700 <rdar://problem/113883375> 1984465 4 ashvayka 2023-10-11 17:03:24 -0700 Hey John, thanks for filing the bugs and providing super well-written test case! Per https://bugzilla.mozilla.org/show_bug.cgi?id=1557611#c7, the difference that was observed in 2019 was due to not all browsers (yet) implementing the spec change: https://github.com/tc39/ecma262/pull/1250. All browsers, including Safari 16.1, are passing the tests. 371556 2019-06-06 21:29:07 -0700 2019-06-06 21:29:07 -0700 Test demonstrating differences in async / promise behavior test2.html text/html 3780 johnplaisted PHNjcmlwdD4KYXN5bmMgZnVuY3Rpb24gdGVzdFNhZmFyaUZpcmVGb3hCdWcoKSB7CiAgbGV0IHJl c29sdmU7CiAgY29uc3QgcHJvbWlzZSA9IG5ldyBQcm9taXNlKChyKSA9PiByZXNvbHZlID0gcik7 CgogIGxldCBkb25lID0gZmFsc2U7CiAgYXN5bmMgZnVuY3Rpb24gaGVscGVyKCkgewogICAgYXdh aXQgcHJvbWlzZTsKICAgIGRvbmUgPSB0cnVlOwogIH0KCiAgaGVscGVyKCk7CgogIC8vIFF1ZXVl OiBbXQogIHJlc29sdmUoKTsgLy8gUXVldWU6IFtyZXNvbHZlIFAwICh0aGVuIGRvbmUpXQogIGF3 YWl0IDA7IC8vIFF1ZXVlOiBbcmVzb2x2ZSBQMCAodGhlbiBkb25lKSwgdGhpcyBhd2FpdCAodGhl biBhc3NlcnQpXQoKICAvLyBJIGRvIG5vdCBoYXZlIGFueSB0aGVvcmllcyBhcyB0byB3aHkgdGhp cyBmYWlscy4KICAvLyBDbGVhcmx5IHRoaXMgb3V0ZXIgZnVuY3Rpb24gYGF3YWl0c2Agc2Vjb25k LCBhbmQgdGhlIGZpcnN0IGlzIHJlc29sdmVkIGFscmVhZHksIGFuZCB0aGUgdGVzdEFzeW5jT3Jk ZXIKICAvLyBiZWxvdyBjb25maXJtcyB0aGF0IChvbiB0aGUgYnJvd3NlcnMgd2l0aCB0aGUgYnVn KSB0aGUgYXdhaXQgb3JkZXIKICAvLyBkZXRlcm1pbmVzIHRoZSBjYWxsYmFjayBvcmRlci4gVGhl c2Ugc2VlbSBhbG1vc3QgaW4gY29uZmxpY3Q/CiAgLy8gSGVyZSB0aGUgYXdhaXQgQU5EIHJlc29s dmUgb3JkZXJzIGJhc2ljYWxseSBtYXRjaCwgeWV0IHRoZSBjb250aW51YXRpb24gb3JkZXIKICAv LyBpcyBjb21wbGV0ZWx5IHRoZSBvcHBvc2l0ZT8KICAvLyBNYXliZSBpdCBpcyBiZWNhdXNlIHRl c3RBc3luY09yZGVyIG9ubHkgdXNlcyBwcm9taXNlcywgYnV0IGFib3ZlCiAgLy8gdGhlcmUncyBh biBgYXdhaXQgMGA/CiAgaWYgKGRvbmUpIGFsZXJ0KCdhc3luYyB0ZXN0IHBhc3NlZCcpOwogIGVs c2UgYWxlcnQoJ2FzeW5jIHRlc3QgZmFpbGVkJyk7Cn0KCmZ1bmN0aW9uIHRlc3RTYWZhcmlGaXJl Rm94QnVnX3Byb21pc2VzKCkgewogIGxldCByZXNvbHZlOwogIGNvbnN0IHByb21pc2UgPSBuZXcg UHJvbWlzZSgocikgPT4gcmVzb2x2ZSA9IHIpOwoKICBsZXQgZG9uZSA9IGZhbHNlOwogIGZ1bmN0 aW9uIGhlbHBlcigpIHsKICAgIHByb21pc2UudGhlbigoKSA9PiB7CiAgICAgIGRvbmUgPSB0cnVl OwogICAgfSk7CiAgfQoKICBoZWxwZXIoKTsKCiAgLy8gUXVldWU6IFtdCiAgcmVzb2x2ZSgpOyAv LyBRdWV1ZTogW3Jlc29sdmUgUDAgKHRoZW4gZG9uZSldCiAgcmV0dXJuIFByb21pc2UucmVzb2x2 ZSgpLnRoZW4oKCkgPT4geyAvLyBRdWV1ZTogW3Jlc29sdmUgUDAgKHRoZW4gZG9uZSksCiAgICAg ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAvLyB0aGlzIHByb21pc2UgKHRoZW4g YXNzZXJ0KV0KCiAgICBpZiAoZG9uZSkgYWxlcnQoJ3Byb21pc2UgdGVzdCBwYXNzZWQnKTsKICAg IGVsc2UgYWxlcnQoJ3Byb21pc2UgdGVzdCBmYWlsZWQnKTsKICB9KTsKfQoKY2xhc3MgUmVzb2x2 ZXIgewogIGNvbnN0cnVjdG9yKCkgewogICAgdGhpcy5wcm9taXNlID0gbmV3IFByb21pc2UociA9 PiB0aGlzLnJlc29sdmUgPSByKTsKICB9Cn0KICAKYXN5bmMgZnVuY3Rpb24gdGVzdEFzeW5jT3Jk ZXIoCiAgaW52ZXJ0UHJvbWlzZUNyZWF0aW9uLAogIGludmVydENhbGxzLAogIGludmVydFJlc29s dmUKKSB7CiAgbGV0IGEsIGI7CiAgaWYgKGludmVydFByb21pc2VDcmVhdGlvbikgewogICAgYiA9 IG5ldyBSZXNvbHZlcigpOwogICAgYSA9IG5ldyBSZXNvbHZlcigpOwogIH0gZWxzZSB7CiAgICBh ID0gbmV3IFJlc29sdmVyKCk7CiAgICBiID0gbmV3IFJlc29sdmVyKCk7CiAgfQogIGNvbnN0IGFy ciA9IFtdOwogIGFzeW5jIGZ1bmN0aW9uIGhlbHBlcihyLCBpKSB7CiAgICBhd2FpdCByLnByb21p c2U7CiAgICBhcnIucHVzaChpKTsKICB9CgogIGNvbnN0IHByb21pc2VzID0gW107CgogIGlmIChp bnZlcnRDYWxscykgewogICAgcHJvbWlzZXMucHVzaChoZWxwZXIoYiwgMSkpOwogICAgcHJvbWlz ZXMucHVzaChoZWxwZXIoYSwgMCkpOwogIH0gZWxzZSB7CiAgICBwcm9taXNlcy5wdXNoKGhlbHBl cihhLCAwKSk7CiAgICBwcm9taXNlcy5wdXNoKGhlbHBlcihiLCAxKSk7CiAgfQoKICBpZiAoaW52 ZXJ0UmVzb2x2ZSkgewogICAgYi5yZXNvbHZlKCk7CiAgICBhLnJlc29sdmUoKTsKICB9IGVsc2Ug ewogICAgYS5yZXNvbHZlKCk7CiAgICBiLnJlc29sdmUoKTsKICB9CiAgYXdhaXQgUHJvbWlzZS5h bGwocHJvbWlzZXMpOwogIHJldHVybiBhcnJbMF07Cn0KICAKZnVuY3Rpb24gdGVzdFByb21pc2VP cmRlcigKICAgIGludmVydFByb21pc2VDcmVhdGlvbiwKICAgIGludmVydENhbGxzLAogICAgaW52 ZXJ0UmVzb2x2ZQogICkgewogICAgbGV0IGEsIGI7CiAgICBpZiAoaW52ZXJ0UHJvbWlzZUNyZWF0 aW9uKSB7CiAgICAgIGIgPSBuZXcgUmVzb2x2ZXIoKTsKICAgICAgYSA9IG5ldyBSZXNvbHZlcigp OwogICAgfSBlbHNlIHsKICAgICAgYSA9IG5ldyBSZXNvbHZlcigpOwogICAgICBiID0gbmV3IFJl c29sdmVyKCk7CiAgICB9CiAgICBjb25zdCBhcnIgPSBbXTsKICAgIGZ1bmN0aW9uIGhlbHBlcihy LCBpKSB7CiAgICAgIHJldHVybiByLnByb21pc2UudGhlbigoKSA9PiBhcnIucHVzaChpKSk7CiAg ICB9CgogICAgY29uc3QgcHJvbWlzZXMgPSBbXTsKCiAgICBpZiAoaW52ZXJ0Q2FsbHMpIHsKICAg ICAgcHJvbWlzZXMucHVzaChoZWxwZXIoYiwgMSkpOwogICAgICBwcm9taXNlcy5wdXNoKGhlbHBl cihhLCAwKSk7CiAgICB9IGVsc2UgewogICAgICBwcm9taXNlcy5wdXNoKGhlbHBlcihhLCAwKSk7 CiAgICAgIHByb21pc2VzLnB1c2goaGVscGVyKGIsIDEpKTsKICAgIH0KCiAgICBpZiAoaW52ZXJ0 UmVzb2x2ZSkgewogICAgICBiLnJlc29sdmUoKTsKICAgICAgYS5yZXNvbHZlKCk7CiAgICB9IGVs c2UgewogICAgICBhLnJlc29sdmUoKTsKICAgICAgYi5yZXNvbHZlKCk7CiAgICB9CiAgICByZXR1 cm4gUHJvbWlzZS5hbGwocHJvbWlzZXMpLnRoZW4oKCkgPT4gYXJyWzBdKTsKICB9Cgphc3luYyBm dW5jdGlvbiB0ZXN0KGZuLCBtb2RlLCBraW5kKSB7CiAgY29uc3Qgbm9DaGFuZ2VzID0gYXdhaXQg Zm4oZmFsc2UsIGZhbHNlLCBmYWxzZSk7CiAgY29uc3QgaW52ZXJ0ZWRQcm9taXNlQ3JlYXRpb24g PSBhd2FpdCBmbih0cnVlLCBmYWxzZSwgZmFsc2UpOwogIGNvbnN0IGludmVydGVkQ2FsbHMgPSBh d2FpdCBmbihmYWxzZSwgdHJ1ZSwgZmFsc2UpOwogIGNvbnN0IGludmVydGVkUmVzb2x2ZSA9IGF3 YWl0IGZuKGZhbHNlLCBmYWxzZSwgdHJ1ZSk7CgogIGlmIChub0NoYW5nZXMgIT09IGludmVydGVk UHJvbWlzZUNyZWF0aW9uKSB7CiAgICBhbGVydCgnUHJvbWlzZSBjcmVhdGlvbiBvcmRlciBhZmZl Y3RzICcgKyBtb2RlKTsKICB9CgogIGlmIChub0NoYW5nZXMgIT09IGludmVydGVkQ2FsbHMpIHsK ICAgIGFsZXJ0KGtpbmQgKyAnIG9yZGVyIGFmZmVjdHMgJyArIG1vZGUpOwogIH0KCiAgaWYgKG5v Q2hhbmdlcyAhPT0gaW52ZXJ0ZWRSZXNvbHZlKSB7CiAgICBhbGVydCgncmVzb2x2ZSgpIG9yZGVy IGFmZmVjdHMgJyArIG1vZGUpOwogIH0KfQoKYXN5bmMgZnVuY3Rpb24gbWFpbigpIHsKICBhd2Fp dCB0ZXN0U2FmYXJpRmlyZUZveEJ1ZygpOwogIGF3YWl0IHRlc3RTYWZhcmlGaXJlRm94QnVnX3By b21pc2VzKCk7CiAgYXdhaXQgdGVzdCh0ZXN0QXN5bmNPcmRlciwgJ2FzeW5jJywgJ2F3YWl0Jyk7 CiAgYXdhaXQgdGVzdCh0ZXN0UHJvbWlzZU9yZGVyLCAncHJvbWlzZXMnLCAndGhlbigpJyk7Cn0K bWFpbigpOwo8L3NjcmlwdD4K