Bug 253423 – Regression(248952@main) setInterval and setTimeout order isn't respected when timeout is 0

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore Misc.

[Kaiido]

Created attachment 465310 [details]
Test case

Online test case: https://jsfiddle.net/7g5f0cLz/
1. Queue a callback using setInterval(cb1, 0);
2. Queue a callback using setTimeout(cb2, 0);

The callback queued through setTimeout() is executed before the one queued through setInterval().
You can see this StackOverflow answer of mine https://stackoverflow.com/a/75646343/3702797 for a walk-through of the specs showing how this behavior is wrong. Basically, with the same ms value, the order should be respected.

Passing another ms value than 0 will make it behave normally.

[Ahmad Saleem]

I am able to reproduce this on WebKit ToT (261247@main) and also Chrome Canary 113 also show incorrect results:

setTimeout()
setInterval()

Only Firefox Nightly 112 is giving 'Expected' result.

[Kaiido]

> Chrome Canary 113 also show incorrect results

Yes, this certainly comes from https://bugs.webkit.org/show_bug.cgi?id=221124 which removed the clamping of setTimeout( ,0) to 1ms, following what Chrome was going to do to.  
They've got the same issue and it's been reported at https://crbug.com/1421612 I guess @Wanming.Lin might chime in here too. I'll mention this issue in the CRBUG too since they seem very related.

[Radar WebKit Bug Importer]

<rdar://problem/106576260>

[Cameron McCormack (:heycam)]

Maybe we can make it so that setInterval(..., 0) will fire the callback immediately (i.e. honoring the 0ms) the first time, and at the clamped 1ms interval afterwards?

[Chris Dumez]

Pull request: https://github.com/WebKit/WebKit/pull/14499

[EWS]

Committed 264701@main (09e6c5eb406c): <https://commits.webkit.org/264701@main>

Reviewed commits have been landed. Closing PR #14499 and removing active labels.

[Fujii Hironori]

fast/dom/Window/setInterval-setTimeout-zero-ordering.html is flaky.
https://results.webkit.org/?suite=layout-tests&test=fast%2Fdom%2FWindow%2FsetInterval-setTimeout-zero-ordering.html