RESOLVED FIXED 246526
[Fetch API] Headers iteration should not happen on cached headers list 
https://bugs.webkit.org/show_bug.cgi?id=246526
Summary [Fetch API] Headers iteration should not happen on cached headers list
Raphael Kubo da Costa (:rakuco)
Reported 2022-10-14 09:56:01 PDT
See https://github.com/web-platform-tests/wpt/pull/36455 FetchHeaders::Iterator seems to cache a FetchHeaders' keys at the time iteration starts, so if the same instance is modified during iteration not all changes will be visible.
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Radar WebKit Bug Importer
Comment 1 2022-10-17 00:01:56 PDT
<rdar://problem/101235580>
youenn fablet
Comment 2 2022-10-17 00:50:07 PDT
Pull request: https://github.com/WebKit/WebKit/pull/5437
Anne van Kesteren
Comment 3 2022-10-17 01:38:40 PDT
Raphael, did you happen to check `FormData` and `URLSearchParams` as well? This might benefit from testing in each API with `iterable<>` given how it's implemented.
EWS
Comment 4 2022-10-17 12:06:43 PDT
Committed 255639@main (68f5a2f24c94): <https://commits.webkit.org/255639@main> Reviewed commits have been landed. Closing PR #5437 and removing active labels.
Raphael Kubo da Costa (:rakuco)
Comment 5 2022-10-18 12:02:59 PDT
(In reply to Anne van Kesteren from comment #3) > Raphael, did you happen to check `FormData` and `URLSearchParams` as well? > This might benefit from testing in each API with `iterable<>` given how it's > implemented. URLSearchParams is covered by https://github.com/web-platform-tests/wpt/blob/master/webidl/ecmascript-binding/iterator-invalidation-foreach.html (I actually based the Fetch tests on it). I've submitted https://github.com/web-platform-tests/wpt/pull/36532 to cover FormData. I haven't checked it in depth, but I think all engines implement them correctly because their "value pairs to iterate over" are just their internal name-value lists. Things get trickier with Headers because it's one of the few cases where the value pairs require modification to the internal data structure. AFAICS only a handful of interfaces do that: Headers, MediaKeyStatusMap (possibly), XRHand (also possibly), and StylePropertyMap (it's CSS so I have close to no idea :-).
Anne van Kesteren
Comment 6 2022-10-19 02:00:46 PDT
Thanks Raphael, much appreciated!
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