[tooltip] Reset preventUnmountOnClose on reopen

[michaldudak]

Summary

• Reset the tooltip store's prevented-unmount flag when the popup opens again.
• Prevent one preventUnmountOnClose() close from making later closes stay mounted forever.
• Add regression coverage for a prevented close followed by a normal close.

Bug

Calling preventUnmountOnClose() latches preventUnmountingOnClose permanently. After one prevented close, later normal closes can keep the tooltip positioner mounted forever instead of unmounting after close completion.

Reproduction

• Before: https://codesandbox.io/s/rdf8dy?file=/src/App.tsx
• After: https://codesandbox.io/s/r4wzg3?file=/src/App.tsx

Test plan

• pnpm test:jsdom TooltipRoot --no-watch
• pnpm test:chromium TooltipRoot --no-watch

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4885
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4885
  

commit: 00e1c8f

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+106B(+0.02%)	🔺+27B(+0.02%)

Details of bundle changes

Performance

Total duration: 1,259.24 ms -132.41 ms^(-9.5%) | Renders: 50 ⁽⁺⁰⁾ | Paint: 1,929.59 ms -199.47 ms^(-9.4%)

Test	Duration	Renders
Tooltip mount (300 contained roots)	45.94 ms ▼-16.25 ms(-26.1%)	1 (+0)

11 tests within noise — details

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[michaldudak]

Codex Review (GPT-5.5)

Reviewed the full PR diff for #4885 against freshly fetched upstream/master. Dominant type: bug-fix; the patch is narrow and targets the latched preventUnmountOnClose() state after a prevented tooltip close.

1. Bugs / Issues (None)

I did not find any concrete branch-relevant bugs or regressions in the implementation.

Root Cause & Patch Assessment

The fix resets preventUnmountingOnClose only on a closed-to-open transition, which preserves the current prevented close while preventing the flag from leaking into later close cycles. Keeping the reset inside useOpenStateTransitions also makes the shared popup lifecycle behavior consistent for the other popup primitives that use the same utility.

Repo Conventions / Cleanliness Assessment

The change follows the repo’s hook utility guidance by using useIsoLayoutEffect, and the dependency list is explicit. No public API, docs-generated types, or error messages were changed.

Test Coverage Assessment

I ran pnpm test:jsdom TooltipRoot --no-watch, pnpm test:chromium TooltipRoot --no-watch, pnpm eslint, and git diff --check; all passed. The new regression test runs through the existing contained, detached, and multiple-detached tooltip variants, which is good coverage for the changed lifecycle path. I did not separately transplant the new test onto upstream/master to prove the red/green failure at base.

Recommendation

Approve ✅

The patch addresses the root cause cleanly, the regression coverage matches the reported failure, and the targeted validation passed.