[DevTools] Only block child Suspense boundaries if the parent has all shared suspenders removed

[everettbu]

Mirror of facebook/react#35737
Original author: eps1lon

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Summary

Stacked on react/react#35736

A Suspense boundary is considered unblocked by I/O removal if no more children (until the next Suspense boundary) are blocked on the same I/O. However, we used to unblock if at least one children with this I/O was removed. Now we check if no more children are blocked on the same I/O.

This was probably an oversight. The unblocking should happen in the same codeblock that checks if all dependencies are removed.

Found with Claude + Opus 4.6

How did you test this change?

• added test (see first commit for current behavior vs 2nd commit for changed behavior)

[greptile-apps]

Greptile Overview

Greptile Summary

This PR tightens the DevTools Suspense “unblocking” logic so child Suspense boundaries are only reconsidered for unblocking after the parent has actually removed the last remaining dependency for a given I/O entry. Previously, unblocking could be triggered even when some children were still suspended on that same I/O, which could incorrectly mark child boundaries as having unique suspenders.

A new store test exercises a stacked outer/inner Suspense scenario to lock in the corrected behavior and prevent regressions.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk.
• Change is a small, localized logic fix that aligns the unblock step with the verified removal of the final dependency; the accompanying regression test covers the previously incorrect stacked Suspense case.
• No files require special attention

Important Files Changed

Filename	Overview
packages/react-devtools-shared/src/backend/fiber/renderer.js	Moves unblockSuspendedBy() call under the same branch that confirms the IO was fully removed from the Suspense boundary (only after last dependency is deleted), preventing child boundaries from being unblocked prematurely.
packages/react-devtools-shared/src/tests/store-test.js	Adds a regression test covering stacked Suspense boundaries to ensure a parent boundary remains blocking until all children suspended on the same removed I/O are removed, and that the inner boundary only becomes unique after the parent’s unique suspenders are fully gone.

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[everettbu]

Upstream PR was closed or merged. Code is synced via branch mirror.