[radio][checkbox][switch] Reduce bundle size

[atomiks]

Reduces the Radio, Checkbox, and Switch bundle size without changing behavior or the public API. The bundle bot is authoritative for the current size impact.

Runtime-read data-* enum members are inlined so the enums tree-shake out, including the component root mappings and shared validity and transition mappings. Local cleanup and enum-sync tests pin every inlined string to its source enum.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@5223
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@5223
  

commit: 617bad3

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	▼-1.35KB(-0.30%)	▼-434B(-0.30%)

Details of bundle changes

Performance

Total duration: 1,361.35 ms +83.02 ms^(+6.5%) | Renders: 78 ⁽⁺⁰⁾ | Paint: 2,132.01 ms +153.06 ms^(+7.7%)

Test	Duration	Renders
Select mount (200 instances)	179.28 ms 🔺+30.65 ms(+20.6%)	3 (+0)
Select open (500 options)	50.95 ms 🔺+9.26 ms(+22.2%)	14 (+0)

12 tests within noise — details

Metric alarms

Test	Metric	Change
Select open (500 options)	bench:paint	🔺 +21.83 ms
Select open (500 options)	bench:paint#select-open	🔺 +21.83 ms

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[Copilot]

Pull request overview

This PR performs a bundle-size reduction pass across Switch, Radio, Checkbox, and shared internals by replacing runtime enum-member lookups for data-* attributes with inlined string literals, and adds “enum sync” tests to keep the literals and enums aligned without reintroducing runtime references.

Changes:

• Inline frequently-read data-* attribute keys (e.g. data-checked, data-invalid, transition status hooks) so related enums can tree-shake out of consumer bundles.
• Refactor Checkbox state-attribute mapping from a hook to a pure helper, and simplify a few context/default-value patterns.
• Add targeted tests to pin inlined literals to their corresponding enums and to cover a few subtle ARIA/form/StrictMode invariants.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/react/src/switch/stateAttributesMapping.ts	Inline data-checked / data-unchecked keys in the Switch state mapping.
packages/react/src/switch/root/SwitchRoot.tsx	Remove mergeProps usage for hidden input props and simplify effect deps; keep validation props applied.
packages/react/src/switch/root/SwitchRoot.test.tsx	Add a browser-only regression test to ensure validation/ARIA props survive canceled changes + submit/reset.
packages/react/src/switch/enumSync.test.ts	New test linking inlined Switch data-* literals back to SwitchRootDataAttributes.
packages/react/src/radio/utils/stateAttributesMapping.ts	Inline data-checked / data-unchecked in Radio state mapping.
packages/react/src/radio/root/RadioRoot.tsx	Simplify defaulting of group-context callbacks via destructuring defaults.
packages/react/src/radio/enumSync.test.ts	New test linking inlined Radio data-* literals back to RadioRootDataAttributes.
packages/react/src/radio-group/RadioGroup.tsx	Simplify aria-labelledby fallback computation and trim redundant context value fields.
packages/react/src/radio-group/RadioGroup.test.tsx	Add regression coverage for aria-labelledby precedence updates as labels/legends mount/unmount/replace.
packages/react/src/internals/useAnimationsFinished.ts	Inline transition “starting style” attribute key to avoid enum runtime reference.
packages/react/src/internals/stateAttributesMapping.ts	Inline transition hook attribute keys so TransitionStatusDataAttributes can tree-shake.
packages/react/src/internals/stateAttributesMapping.test.ts	New tests syncing inlined transition + validity mapping literals to their enums.
packages/react/src/internals/field-constants/constants.ts	Inline data-valid / data-invalid in shared field validity mapping.
packages/react/src/checkbox/utils/useStateAttributesMapping.ts	Remove hook-based mapping helper (no longer needed).
packages/react/src/checkbox/utils/getCheckboxStateAttributesMapping.ts	New pure helper returning Checkbox state-attribute mapping with inlined data-* keys.
packages/react/src/checkbox/root/CheckboxRoot.tsx	Switch to new mapping helper and apply minor cleanup (e.g. Symbol() init).
packages/react/src/checkbox/indicator/CheckboxIndicator.tsx	Reuse the new mapping helper and remove redundant validity mapping spread.
packages/react/src/checkbox/enumSync.test.ts	New test linking inlined Checkbox data-* literals back to CheckboxRootDataAttributes.
packages/react/src/checkbox-group/useCheckboxGroupParent.ts	Use shared EMPTY_ARRAY, simplify filter logic, and remove redundant returned indeterminate field.
packages/react/src/checkbox-group/CheckboxGroupContext.ts	Simplify useCheckboxGroupContext to a direct context read (internal helper).
packages/react/src/checkbox-group/CheckboxGroup.tsx	Simplify uncontrolled defaultValue computation and reuse EMPTY_ARRAY.
packages/react/src/checkbox-group/CheckboxGroup.test.tsx	Add StrictMode regression test ensuring omitted defaults don’t leak between groups.

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