chore(action-button): implement accessibility features

[cdransf]

Description

Implements Phases 2–4 of the 1st-gen → 2nd-gen swc-action-button migration:

• Phase 2 (setup): Directory scaffold, file stubs, and package exports for the new swc-action-button component in both 2nd-gen/packages/core (types) and 2nd-gen/packages/swc (component, stories, tests).
• Phase 3 (API): Full TypeScript implementation of ActionButton extending ButtonBase, including the xs–xl size scale, quiet, static-color, and the no-default-attribute size behavior via a _size=null sentinel.
• Phase 4 (accessibility): ARIA passthrough for aria-haspopup / aria-expanded (forwarded to the inner <button>, then stripped from the host), a pending-icon element for Phase 5 CSS targeting, and aligned JSDoc across all public members.

Also adds @deprecated JSDoc and window.__swc.warn() runtime warnings to the 1st-gen sp-action-button for emphasized, holdAffordance, selected, and toggles — signaling the migration path to consumers.

Motivation and context

swc-action-button is a high-frequency component used in toolbars, action groups, and icon-first chrome. The 2nd-gen version removes toggle semantics (toggles, selected, aria-pressed), the link API (href), and the consumer-controlled role override — all of which were identified in the migration analysis as footguns or anti-patterns. Toggle / selection UX moves to the forthcoming swc-toggle-button / swc-toggle-button-group.

Related issue(s)

• SWC-2044

Screenshots (if appropriate)

N/A — no visual output yet (CSS is a stub; Phase 5 adds styling).

Author's checklist

• I have read the CONTRIBUTING and PULL_REQUESTS documents.
• I have reviewed the Accessibility Practices for this feature, see: Aria Practices
• I have added automated tests to cover my changes.
• I have included a well-written changeset if my change needs to be published.
• I have included updated documentation if my change required it.

Note on tests: Phase 6 adds play-function assertions and ARIA snapshot tests. The test files created here (action-button.test.ts, action-button.a11y.spec.ts) are stubs intentionally left empty until the styling phase is complete and there is a renderable component to assert against.

Reviewer's checklist

• Includes a Github Issue with appropriate flag or Jira ticket number without a link
• Includes thoughtfully written changeset if changes suggested include patch, minor, or major features
• Automated tests cover all use cases and follow best practices for writing
• Validated on all supported browsers
• All VRTs are approved before the author can update Golden Hash

Manual review test cases

• 1st-gen deprecation warnings fire in dev mode

  1. Open any 1st-gen Storybook story for sp-action-button
  2. Open the browser console
  3. Set emphasized, holdAffordance, selected, or toggles on the element
  4. Expect: a window.__swc.warn() deprecation warning appears for each

• 2nd-gen size attribute not reflected by default

  1. Open the 2nd-gen Storybook Playground for swc-action-button
  2. Inspect the host element in DevTools
  3. Expect: no size attribute on the host until one is explicitly set; button.size JS property returns 'm'

• ARIA passthrough: aria-haspopup / aria-expanded forwarded and stripped

  1. In a 2nd-gen Storybook story, set aria-haspopup="true" and aria-expanded="false" on a <swc-action-button>
  2. Inspect the host element in DevTools
  3. Expect: host carries neither aria-haspopup nor aria-expanded
  4. Inspect shadowRoot.querySelector('button') in the console
  5. Expect: the inner <button> carries both aria-haspopup="true" and aria-expanded="false"

Device review

• Did it pass in Desktop?
• Did it pass in (emulated) Mobile?
• Did it pass in (emulated) iPad?

Accessibility testing checklist

Required: Complete each applicable item and document your testing steps.

• Keyboard (required — document steps below)

  1. Open the 2nd-gen Storybook Playground for swc-action-button
  2. Tab to the component
  3. Expect: focus ring visible on the inner <button>, not the host; shadowRoot.activeElement returns the inner <button>
  4. Press Enter and Space
  5. Expect: click event fires and bubbles to the host
  6. Set pending attribute; tab back to the button
  7. Expect: button is still in tab order; Enter / Space do not fire click
  8. Set disabled attribute; tab through the page
  9. Expect: button is skipped entirely

• Screen reader (required — document steps below)

  1. Open the 2nd-gen Storybook Playground for swc-action-button with VoiceOver (macOS) or NVDA (Windows)
  2. Tab to the default <swc-action-button>Edit</swc-action-button>
  3. Expect: announces "Edit, button"
  4. Tab to an icon-only button with accessible-label="Format"
  5. Expect: announces "Format, button"; host element is not announced separately
  6. Set aria-haspopup="true" and aria-expanded="false" on the button
  7. Expect: announces "Edit, button, has popup" (or platform equivalent)
  8. Set pending attribute
  9. Expect: announces something like "Edit, busy, button" (aria-disabled state)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 5e65e8d

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[github-actions]

📚 Branch Preview Links

• Documentation Site (first-gen)
• Storybook (first-gen)
• Storybook (second-gen)

🔍 First Generation Visual Regression Test Results

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

• Spectrum | Light | Medium | LTR
• Spectrum | Dark | Large | RTL
• Express | Light | Medium | LTR
• Express | Dark | Large | RTL
• Spectrum-two | Light | Medium | LTR
• Spectrum-two | Dark | Large | RTL
• High Contrast Mode | Medium | LTR

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