Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: f8dd5342df32e060f207ff181494e0308d4f7fee
https://github.com/WebKit/WebKit/commit/f8dd5342df32e060f207ff181494e0308d4f7fee
Author: Youenn Fablet <[email protected]>
Date: 2026-01-07 (Wed, 07 Jan 2026)
Changed paths:
M LayoutTests/TestExpectations
M Source/WebCore/bindings/js/JSDOMPromiseDeferred.cpp
Log Message:
-----------
imported/w3c/web-platform-tests/fetch/api/response/response-body-read-task-handling.html
is flaky without JS built-in streams
rdar://165386906
https://bugs.webkit.org/show_bug.cgi?id=303084
Reviewed by Chris Dumez.
When resolving a promise, we synchronously get the `then` value, which can
trigger JavaScript execution.
We should normally do this execution in an event loop task as per spec, but we
are not always doing so.
If resolving a promise outside of an event loop task, we would execute the then
getter with an empty execution context stack.
In that case, if calling a callback from the JS code, for instance as done by
response-body-read-task-handling.html with acceptNode callback,
we would trigger a microtask checkpoint when exiting of the acceptNode
callback, as the execution context stack is empty,
as per https://webidl.spec.whatwg.org/#call-a-user-objects-operation step 15,
which calls
https://html.spec.whatwg.org/multipage/webappapis.html#clean-up-after-running-script.
To still allow to resolve a promise outside of an event loop task without
causing unnecessary microtask checkpoints, we are making sure that the
execution context stack is not empty.
This is done by setting the currentState of threadGlobalDataSingleton to a non
null value before resolving the promise if the currentState is nullptr.
We make sure to set the currentState back to nullptr just after the promise
resolution.
* LayoutTests/TestExpectations:
* Source/WebCore/bindings/js/JSDOMPromiseDeferred.cpp:
(WebCore::DeferredPromise::callFunction):
Canonical link: https://commits.webkit.org/305209@main
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