DevTools: Don't fallback to nearest host descendants when tracing updates

[pedr0fontoura]

Summary

Components that didn't re-render were being highlighted with the Highlight updates when components render. DevTools option enabled.

I removed the offending code, which solved the problem. I don't fully understand what that code was doing, so I would like to hear the opinion of someone more familiar with it.

Screen.Recording.2025-02-25.at.14.34.10.mov

How did you test this change?

I added a repro example in the DevTools test harness. You can find the related code at packages/react-devtools-shell/src/app/TraceUpdateRepro/index.js

After the change:

Screen.Recording.2025-02-25.at.14.42.56.mov

You can test this by running the react-devtools-inline and react-devtools-shell.

I don't expect this PR to land exactly like this, but rather to serve as a repro and point to a possible fix. I would appreciate any feedback or guidance to improve it.

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[rickhanlonii]

instead of depending on the value changing, can you add a console.log to the component in render? You should see that the log is being hit, so it is rendering, but it bails out.

[pedr0fontoura]

instead of depending on the value changing, can you add a console.log to the component in render? You should see that the log is being hit, so it is rendering, but it bails out.

The log doesn't seem to be hit. Just on the initial render. I also tried with a breakpoint on the function body. @rickhanlonii

[pedr0fontoura]

I'm trying to wrap my head around the bailout...

Why would the ShouldNotReRender components even be considered to render if its parent didn't update and no state change happened inside the component?

Also, why is the behavior different between the "top-level" ShouldNotReRender and the ones nested inside divs?

[hoxyq]

Thanks for reporting this, this actually looks like a bug in the logic for React DevTools for this exact rare case

I will try to take a better look at later this / next week and follow up