feat(commons/text): support form-associated labels via element internals#5182
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Detect form-associated custom elements in nativeTextAlternative and add labelText, and resolve labels from internals.labels in labelText. Both are gated by the elementInternals run option. Closes issue #5045
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Pull request overview
This PR updates axe-core’s commons/text accessible-name computation to recognize native <label> associations for form-associated custom elements by leveraging ElementInternals.labels (when available and enabled via the existing elementInternals feature flag).
Changes:
- Extend
nativeTextAlternativeto appendlabelTextfor form-associated custom elements detected viaElementInternals. - Update
labelTextto preferinternals.labels(authoritative explicit + implicit labels) and fall back to DOM-based lookup otherwise. - Add/expand test utilities and unit tests covering explicit/implicit/multiple labels, deduping, global map internals, and Shadow DOM scenarios.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
lib/commons/text/native-text-alternative.js |
Detects form-associated custom elements via internals and conditionally adds labelText as a naming method. |
lib/commons/text/label-text.js |
Uses ElementInternals.labels (guarded) to compute label text, falling back to existing DOM resolution. |
test/testutils.js |
Introduces testutils-form-element (form-associated) for label-related tests. |
test/commons/text/native-text-alternative.js |
Adds unit tests validating label pickup + feature-flag gating for form-associated custom elements. |
test/commons/text/label-text.js |
Adds unit tests for internals-based label resolution (including global map + Shadow DOM). |
test/commons/aria/get-role.js |
Adds regression tests clarifying presentational role inheritance behavior with ElementInternals roles. |
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| const internals = virtualNode.elementInternals; | ||
| if (internals && !methods.includes('labelText')) { | ||
| try { | ||
| // `labels` throws on custom elements that aren't form-associated | ||
| internals.labels; | ||
| textMethods.push(nativeTextMethods.labelText); | ||
| } catch { | ||
| // not a form-associated custom element | ||
| } | ||
| } |
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| const { actualNode } = target; | ||
| const internals = actualNode._internals; | ||
| // remove the property protocol so the global map is the only source. | ||
| // elementInternals is read lazily, so the first read happens below | ||
| delete actualNode._internals; | ||
| globalThis._elementInternals = new WeakMap(); | ||
| globalThis._elementInternals.set(actualNode, internals); | ||
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| assert.equal(labelText(target), 'My explicit label'); | ||
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| delete globalThis._elementInternals; | ||
| }); |
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| it('does not add a label when element internals are disabled', () => { | ||
| axe._enableElementInternals = false; | ||
| const vNode = queryFixture(` | ||
| <label for="target">My explicit label</label> | ||
| <testutils-form-element id="target"></testutils-form-element> | ||
| `); | ||
| assert.equal(nativeTextAlternative(vNode), ''); | ||
| axe._enableElementInternals = true; | ||
| }); |
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Summary
Form-associated custom elements (
static formAssociated = true+attachInternals()) can be labeled with native<label>elements, which the browser exposes throughElementInternals.labels. axe-core's accessible-name computation dropped these labels entirely, because:nativeTextAlternativebuilds its naming methods from the element spec, andgetElementSpec()returns{}for custom element names — solabelTextwas never invoked for a custom element.labelTextonly looked at the DOM byid(label[for]) / ancestor wrapping.This wires up the proposal's final step.
Changes
native-text-alternative.js—findTextMethodsdetects a form-associated custom element viaElementInternalsand appendslabelText.label-text.js—labelTextreadsinternals.labelsdirectly when present (the authoritative, complete set of explicit + implicit labels), falling back to the existing DOM resolution otherwise.ElementInternals.labelsthrowsNotSupportedErroron a custom element that isn't form-associated, so both reads are guarded with try/catch. Both paths are gated by the existingelementInternalsrun option — with the flag off,vNode.elementInternalsisundefinedand behavior is unchanged.Why
internals.labels(not the DOM lookup)?It's the browser-authoritative association and is the complete set — it already includes the ancestor-wrapping label. Routing it through the existing explicit + implicit merge would count a wrapping label twice, so
labelTextuses the internals list exclusively when present.Out of scope
checks/label(explicit/implicit) — no change needed. They resolve labels vialabel[for=id]/closest('label'), which already cover custom elements, and thelabelrule selector isinput, textareaanyway. Matches the proposal ("rules that look at implicit/explicit labels will not need to be updated") and feat(checks/label): support ARIA element internals properties #5170 leaving those checks untouched.<label for>— labelable-ness/role territory (ElementInternals: updateimplicitRoleto usegetElementInternals#5039), pre-existing.getResolvedRefs(feat(dom/getResolvedRefs): new function to get the resolved virtual nodes of idrefs #5151) — native<label>/forassociation isn't an ARIA idref, so it doesn't apply here.Testing
test/testutils.js— new sharedtestutils-form-element(form-associated).label-text.js— explicit, implicit, multiple, implicit+explicit dedup, global-map protocol, non-form-associated fall-through, Shadow DOM.native-text-alternative.js— explicit/implicit pickup, gating (non-form-associated gets no label), flag-off no-op.No integration test added — this is a
commons/textchange with no rule/check edits; the nearest rule impact (aria-input-field-nameon a role-bearing custom element) depends on role-via-internals selection (#5039), which isn't wired yet.Closes #5045