When "Importing the profile directly from Firefox", exceptions should be more obvious in the UI

[carverdamien]

While I was working on Bug2012154, I had an issue in computeReferenceCPUDeltaPerMs because I was passing an unexpected value for threadCPUDeltaUnit. The exception was thrown in the console but the loading animation was still running. If the UI was properly indicating the issue, it would have saved me the time spent investigating.

┆Issue is synchronized with this Jira Task

[fatadel]

@carverdamien can you share an example profile, please?

[carverdamien]

It's not possible to have a profile because we don't even reach the point where the "share profile" feature is available.

If you want to try to reproduce, maybe raise a fake exception in that function and try to record a profile.

[canova]

I tried to capture a markers-only profile and then remove the profile.meta.sampleUnits.threadCPUDelta field from the json manually. Then tried loading into the profiler by dragging and dropping that.

And it looks like we can actually see the error message there. So it must be more about how we show the error messages when the profiles are coming from webchannel. Normally we have ErrorBoundry component to show the error messages and it's added to root, but not so sure if the error is being thrown outside of the error boundry.

Here's an example profile

[canova]

I was curious so, I compiled Firefox with this line commented out to see if I can reproduce it: https://searchfox.org/firefox-main/rev/3c52c9c886f7b0423001cef86abfafcf97f2b90a/tools/profiler/core/platform.cpp#3549
And I can indeed reproduce.

This is the error:

Uncaught (in promise) Error: Unhandled threadCPUDelta unit in computeReferenceCPUDeltaPerMs.
    y types.ts:25
    zF cpu.ts:88
    y index.js:67
    d defaultMemoize.js:123
    T index.js:81
    d defaultMemoize.js:123
    T index.js:77
    d defaultMemoize.js:123
    aV receive-profile.ts:272
    Redux 2
    Kb receive-profile.ts:214
    Redux 2
    I0 app.ts:172
    gd url-handling.ts:90
    I0 app.ts:170
    Redux 2
    _processInitialUrls UrlManager.tsx:132

Now that I invested some time, I think I know how to fix. This is due to _processInitialUrls and finalizeProfileView inside of it being async and not being properly awaited, and that's why our ErrorBoundary component can't catch the uncaught error that happens in a promise.

This part of the url loading is a bit weird, so I'll write a patch about it and explain it there.