fix(react-breadcrumb): make BreadcrumbButtonBaseProps distribute over the ARIA button union - #36663
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Dmytro Kirpa (dmytrokirpa) merged 6 commits intoSep 3, 2026
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… the ARIA button union
`BreadcrumbButtonBaseProps` was declared with a plain `Omit`:
export type BreadcrumbButtonBaseProps = Omit<BreadcrumbButtonProps, 'size'>;
`BreadcrumbButtonProps` includes `ComponentProps<ButtonSlots>`, whose `root`
slot is `ARIAButtonSlotProps<'a'>` -- a union over `{ as?: 'button' } & button
attrs` and `{ as: 'a' } & anchor attrs`. Plain `Omit` is `Pick<T, Exclude<keyof
T, K>>`, and `keyof` a union keeps only the keys common to every member, so the
omit collapses the union and every anchor-only prop (`href`, `target`, `rel`,
...) disappears from the derived type. `@fluentui/react-button` avoids exactly
this on the same shape by using `DistributiveOmit`
(Button.types.ts:72,84); this makes `react-breadcrumb` consistent with it.
Healed -- all three now type-check against the base surface where none did
before:
<BreadcrumbButton href="#a"> (the spelling react-breadcrumb's
own Default story uses)
<BreadcrumbButton as="a" href="#a">
<BreadcrumbButton as="a" href target rel>
Not changed, and honestly not a regression: a props object literal whose only
property is `href` is still rejected. That is TypeScript weak-type detection --
the `{ as?: 'button' }` union member has no required properties and shares no
property with `{ href }`, so the source only matches the `a` member, which then
demands an explicit `as: 'a'`. It fires identically on the Griffel
`BreadcrumbButtonProps`, and adding any shared property (`children`, which every
real JSX usage has) satisfies it on both. Runtime behaviour is unchanged: this
file declares types only and emits nothing.
etc/react-breadcrumb.api.md regenerated by the build.
Verified: react-breadcrumb type-check + lint pass; react-headless-components-preview
and react-components type-check pass. react-breadcrumb:test is 2 failed / 105
passed both with and without this change (pre-existing @fluentui/react-icons
snapshot drift -- SVG path data and the `fui-Icon` class -- unrelated to it).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013wmpBCYJpDJCLXcScCWz1i
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Aj9uA3rCVgosnh2zNn8qkc
📊 Bundle size report
Unchanged fixtures
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Pull request demo site: URL |
![github-actions[bot]](https://avatars.githubusercontent.com/in/15368?s=60&v=4){kind=small}
…rumbButtonBaseProps
…Type ternary (microsoft#36681) `as ?? href ? 'a' : 'button'` parses as `(as ?? href) ? 'a' : 'button'`, so an explicit `as: 'button'` (truthy) computed controlType 'a' and the ARIA button pipeline emitted the anchor arm (as: 'a', role="button") for a caller who asked for a real <button>. Parenthesize so an explicit `as` short-circuits the href inference, and add a red/green renderHook regression test alongside the existing anchor-arm test.
Contributor
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Dmytro Kirpa (@dmytrokirpa) While adding the base-hook test you asked for, we hit an operator-precedence bug in the same hook: |
Dmytro Kirpa (dmytrokirpa)
approved these changes
Sep 2, 2026
Dmytro Kirpa (dmytrokirpa)
enabled auto-merge (squash)
September 3, 2026 07:49
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BreadcrumbButtonBasePropsis declared as a plainOmit<BreadcrumbButtonProps, 'size'>.BreadcrumbButtonPropsincludesComponentProps<ButtonSlots>, whose root isARIAButtonSlotProps— a distributive union overas: 'button' | 'a'. A plainOmitcollapses that union into a single object type keyed on the intersection of its members, so the anchor arm'shrefdisappears and the anchor spelling ofBreadcrumbButton(the one the component's own Default story uses) no longer type-checks against the base props type.The fix switches to
DistributiveOmit, matching what@fluentui/react-buttonalready does for the same reason. Type-level only — no runtime change — and the widened type is strictly a superset of the current one, so no existing consumer code stops compiling. Theetc/react-breadcrumb.api.mdreport is regenerated to match.Fixes #36645.
Extracted from #36656 per maintainer request — each in-tree fix from that PR as an isolated change.
Also fixes #36681: while adding the requested base-hook test, we found that
controlType'sas ?? href ? 'a' : 'button'parses as(as ?? href) ? 'a' : 'button', so an explicitas: 'button'(truthy) computed'a'and the ARIA button pipeline emitted the anchor arm (<a role="button">). Parenthesized so an explicitasshort-circuits thehrefinference, with a red/green renderHook regression test alongside the existing anchor-arm test.