Bug 243668 – Error stack is incomplete for async call

• Component: JavaScriptCore
• Status: NEW

[Xidorn Quan]

Created attachment 461484 [details]
testcase

Please see the attached testcase. There is a series of async functions, c() calls b() calls a(), but if you open it on Safari, the stack shows:
> [e-mail]:4:18
> @async-error.html:8:13
> asyncFunctionResume@[native code]
> @[native code]
> promiseReactionJobWithoutPromise@[native code]
> promiseReactionJob@[native code]
which is not very useful.

Firefox has a similar issue, but at least it doesn't show things from native code:
> [e-mail]:4:9
> [e-mail]:8:3

Chrome has the best behavior that it can properly track across async frame:
> Error
>     at throwError (async-error.html:4:9)
>     at a (async-error.html:8:3)
>     at async b (async-error.html:11:3)
>     at async c (async-error.html:14:3)

Being able to track across async frame is important for knowing what is the right place to handle an error. Not being able to go across async frame means it is very hard to track the stack for any network errors.

[Xidorn Quan]

I think Firefox had a project for this: https://bugzilla.mozilla.org/show_bug.cgi?id=981514 but it seems to be stalled currently.

[Sam Sneddon [:gsnedders]]

Note that bug 163230 effectively implemented a bunch of this for Web Inspector.

[Devin Rousso]

ive done a *lot* of work lately to fix this (and a few other things) =D
- 252543@main added async stack trace capturing for `queueMicrotask` (when Web Inspector is open)
- 252554@main 252693@main, 252914@main, and 253022@main removed internal functions (e.g. `promiseReactionJob`) from stack traces
- 252630@main makes it so that sync stack traces shown in Web Inspector will now always include any async stack traces

we currently don't capture async stack trace information when Web Inspector is not open, so i'll leave this bug open as consideration for doing that

[Radar WebKit Bug Importer]

<rdar://problem/98666726>