Bug 286060 – REGRESSION: Service Worker downloads being prematurely interrupted since iOS 18.2

• Status: RESOLVED
• Resolution: FIXED
• Component: Service Workers

1) Open this page: https://stat-info.cz/safari-sw-download-tests.html
2) Click on any "Start download" button.
3) The download is automatically interrupted after a few chunks.

iOS 18.1 is the last working version for me.

[Radar WebKit Bug Importer]

<rdar://problem/143065672>

[youenn fablet]

This is working for me using ToT WebKit.

I tried iOS 18.3 Beta 3 - not working. What can I do to help find the issue?

[youenn fablet]

I'll try it on iOS 18.3 to try reproducing, if it reproduces then it means it is probably fixed in ToT.

Issue is still reproducible on iOS 18.4 Beta.

It seems it is triggered by some race condition. If I have predownloaded multiple chunks, sending them to a ServiceWorker right after its activation interrupts the download.

I've prepared a better test to reproduce this issue:
1) Go to https://stat-info.cz/safari-bug286060.html
2) Predownload 5 chunks using the "Download chunk" button.
3) Start the file download using "Open ServiceWorker connection" button.
4) Now the download is automatically interrupted by Safari after writing all predownloaded chunks.

Note 1: The download is successfully completed if you Open ServiceWorker connection first and then you download 10 chunks.
Note 2: Chrome on iOS works fine with predownloaded chunks.

[EWS]

Committed 291712@main (29a25c5dec47): <https://commits.webkit.org/291712@main>

Reviewed commits have been landed. Closing PR #41998 and removing active labels.