Bug 237912

Summary:

REGRESSION(r288307): instanceof value wrong in MutationObserver callback for Safari extensions

Product:

WebKit

Reporter:

Jeff Johnson <opendarwin>

Component:

Bindings

Assignee:

Alexey Shvayka <ashvayka>

Status:

RESOLVED FIXED

Severity:

Blocker

CC:

ashvayka, cdumez, ews-watchlist, jond, saam, timothy, webkit-bug-importer, ysuzuki

Priority:

Keywords:

InRadar

Version:

WebKit Nightly Build

Hardware:

All

OS:

All

See Also:

https://bugs.webkit.org/show_bug.cgi?id=232387

Attachments:

Description	Flags
Sample Xcode project	none
Patch	none

Jeff Johnson

Reported 2022-03-15 11:42:12 PDT

Created attachment 454735 [details] Sample Xcode project This bug occurs with Safari Technology Release 141 (Safari 15.4, WebKit 16614.1.3.7) on macOS 11.6.5. The bug does not occur with Safari 15.3 or Safari 15.4 (released yesterday), only with Safari Technology Preview. The bug is that JavaScript instanceof is returning false when it should return true in the callback of MutationObserver for Safari extensions, both Safari web extensions and Safari app extensions. This bug does not seem to affect scripts in the web pages, only extension scripts. Attached is a sample Safari web extension Xcode project that demonstrates the bug. Just enable the extension, run it on any web site, such as cnn.com, and look at the console log. For HTML <div> elements, it should log true true for instanceof HTMLElement and instanceof HTMLDivElement, but it logs false false in Safari Technology Preview 141. This bug is a massive problem for me, a showstopper for several of my Safari extensions in the App Store. It totally breaks essential functionality in my extensions.

Attachments
Sample Xcode project (324.10 KB, application/zip) 2022-03-15 11:42 PDT, Jeff Johnson	no flags	Details
Patch (9.46 KB, patch) 2022-03-22 09:01 PDT, Alexey Shvayka	no flags	Details Formatted Diff Diff
View All Add attachment proposed patch, testcase, etc.

Jeff Johnson

Comment 1 2022-03-15 11:44:40 PDT

Note that instanceof works correctly in the setTimeout function. It's only wrong in the MutationObserver callback.

Jeff Johnson

Comment 2 2022-03-15 12:10:15 PDT

I can also reproduce with Safari Technology Preview 141 on macOS 12.3 on Apple Silicon. Safari 15.4 (17613.1.17.1.6) is not affected.

Jon Davis

Comment 3 2022-03-15 13:39:52 PDT

Thank you for the bug report. I’ve cc’d some engineers to investigate.

Radar WebKit Bug Importer

Comment 4 2022-03-15 15:12:14 PDT

<rdar://problem/90333276>

Alexey Shvayka

Comment 5 2022-03-22 09:01:29 PDT

Created attachment 455377 [details] Patch

EWS

Comment 6 2022-03-22 13:25:31 PDT

Committed r291694 (248736@main): <https://commits.webkit.org/248736@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 455377 [details].

Note You need to log in before you can comment on or make changes to this bug.