Change:
onHookOperations = (operations: Array<number>) => { if (__DEBUG__) { <del> debug('onHookOperations', operations); </del> <ins> debug( 'onHookOperations', `(${operations.length}) [${operations.join(', ')}]`, ); </ins> } // TODO:

Discussion:
did profiling on a list, that gets updated on each pagination api call. the profiling was done, I moved around in the Profiler to view the Flamegraph to second capture, the Profiler crashed. DevTools version: 4.6.0-
What does this mean? Can you repro this bug? And if so, could you share steps for repro with us?
Sorry for not providing enough details, but even I don't have enough details. This error just popped up when I was profiling my app in React Devtools. I was profiling a normal () list, and it broke when I clicked next button on DevTools, to see the recorded profile. <img width="1149" alt="Screenshot 2020-05-08 at 11 12 50 AM" src="https://user-"About having a repro, I couldn't replicate it myself after that one occurrence, again. Anyways, my assumption is (it could be wrong), one of the list item in the flame graph is getting duplicated somehow, either due to the app it was profiling or due to something else.
Okay. Thanks for clarifying.
If no-one is working on this, I would like to assign myself to investigate and fix the issue (since multiple people have referenced it). Also, If you assign me, Can you please also help me with where to look?
If you'd like to dig into this, we'd be happy to have the help. I don't really have the bandwidth to guide you on it though. Some places you'd want to look at for starters:    And for a general overview of how DevTools works, you can check out this:
This error remains the highest reported DevTools bug but we still don't have a repro case so that I can fix it. Do you remember how to repro the error you saw above? Can you share the steps with me if so? It would be very helpful! Thank you
Hi Will try to replicate it again... It's been a long time since I used the Profiler, so I don't remember much.
Okay, understood! Either way, thanks for checking.
I've got a repro for this over on : When I run this project, I see an error in DevTools: This is very promising! Looks like there's a problem with Suspense and LegacyHidden.

I think the case I'm seeing is this: initial render, a Suspense component is mounted. has an Offscreen child, b'c of how Suspense is implemented internally, but DevTools hides this implementation detail to avoid confusion. (What this actually means is that the DevTools backend never even tells the frontend that the Offscreen component exists.) login, stuff is updated and for some reason, the backend thinks it needs to unmount the Offscreen component (even though the frontend never knew about it). This causes an error to be thrown. Unfortunately this thrown error is not surfaced in the UI so things go on until later, when it causes a downstream error in the Profiler. First step is making that first error visible (done via ). Second step is to figure out why it's happening. Interestingly, if I trim down the repro a to the minimal repro case, then copy that into the React DevTools test harness (with a bleeding edge build of react and react-dom) the bug no longer happens. Edit 1: If I copy it instead into a project created by – with the same major versions of react and react-dom, I can repro the bug. So that's good. Seems like something may have changed on the React side between 17.0.2 and HEAD? Edit 2: One (possibly) significant difference between the two versions is that 17 uses the component beneath but HEAD uses the newer component. I can also repro the same error in the DevTools test shell by swapping with so...
Oooh looks like this may have just been an oversight in our filtering logic. (We filter but not components. Eventually we'll not want to filter but for now, that seems an easy fix.
This bug fix has been released as 4.13.1