@dloizides/a11y

The accessibility platform seam for the dloizides.com RN-web UI kit.

One authored contract in, platform-correct props out — including the hint, which react-native-web otherwise drops silently.

npm install @dloizides/a11y

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The bug this exists to fix

All seven portals are React Native + Expo but ship web only. On web, react-native-web maps accessibilityLabel → aria-label, but accessibilityHint has no ARIA equivalent and is discarded. An element authored like this:

<TouchableOpacity accessibilityLabel="QR code" accessibilityHint="Opens the QR modal" />

renders aria-label + role + tabindex and no hint attribute at all.

The repo-wide rule "every interactive element needs testID + accessibilityLabel + accessibilityHint" therefore bought nothing on web.

It hid for years because a DOM assertion cannot distinguish a threaded hint from a dropped one — both render identically. No test could see it, so nothing ever failed.

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Usage

import { useA11y } from '@dloizides/a11y';

const { a11yProps, hintNode } = useA11y({
  label: 'Save',
  hint: 'Saves the menu and returns to the list',
  role: 'button',
  state: { disabled, busy: loading },
  testID: 'save-button',
});

return (
  <TouchableOpacity {...a11yProps} onPress={onPress}>
    {children}
    {hintNode}
  </TouchableOpacity>
);

hintNode is null on native and when there is no hint, so an unconditional {hintNode} is always correct.

What comes out

authored	native	web
label	accessibilityLabel	aria-label
hint	accessibilityHint	aria-describedby → a rendered, visually-hidden node
role	accessibilityRole (RN vocabulary)	role (ARIA vocabulary — see below)
state	accessibilityState	aria-disabled / -selected / -expanded / -busy / -checked
testID	testID	testID (RN-web emits data-testid)

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Design notes

Why the hint becomes a node, not an attribute

aria-describedby is a pointer. Without a rendered element carrying the id, the attribute references nothing and assistive technology announces nothing. So the description has to genuinely exist in the document — visually hidden, but present.

The node is rendered as a descendant of the host, so it mounts and unmounts with it; a dangling reference to a node that outlived its owner is not possible. It is hidden with position:absolute + 1×1 + overflow:hidden — never display:none, visibility:hidden or opacity:0, all of which risk removing it from the accessibility tree and silently undoing the entire fix.

Known trade-off: the host's raw textContent now includes the hint

The hidden node is a descendant, so host.textContent returns the label and the hint. This is deliberate and the alternatives are worse (a sibling node needs a wrapper element, which changes flex layout; a detached node can outlive its owner).

What it does not change is the accessible name: aria-label takes precedence over content per the ARIA spec, so getByRole('button', { name }) — which is how every Playwright locator in the fleet targets buttons — is unaffected. There is a test pinning exactly this, because the precedence going missing would be a silent E2E-wide breakage.

The residual exposure is any assertion reading raw textContent off a control that renders a hint. At the time of writing no E2E page object does this on a kit Button (the 20 toHaveText/textContent call sites all target badges, errors, titles and status labels). Prefer getByRole(..., { name }) over text-content matching on interactive elements.

Why it can't be forgotten quietly

Three layers, earliest-catching first:

1. One call returns both. You cannot obtain a11yProps without hintNode landing in the same destructure, one identifier away. No separate import to discover.
2. Dev runtime guard. After commit, on web, the hook checks the described-by target is actually in the document and console.errors if not. The failure mode becomes noisy — the one thing the original bug never was.
3. The dual test gate. Web assertions resolve aria-describedby to real text, so a component that dropped the node fails rather than passing vacuously.

Note who calls this: apps never do. They keep passing accessibilityHint to <Button>. Only the kit components call useA11y, which is a small, reviewed surface.

Why the role table is total

RN's role vocabulary and ARIA's overlap but are not the same set. Pass-through produces invalid ARIA, which browsers ignore — failing the same silent way the hint did. The notable divergences:

RN	ARIA	why
header	heading	header is valid ARIA (a landmark) — pass-through would silently turn every heading into a landmark. Worse than dropping it.
search	searchbox	ARIA's search is a landmark; RN's means a search field.
none	presentation
image	img
adjustable	slider
imagebutton, keyboardkey	button	no ARIA equivalent
text, summary	(omitted)	no faithful equivalent — better to say nothing

The table lists every A11yRole explicitly and is typed Record<A11yRole, Role>, so adding a role without deciding its ARIA spelling is a compile error.

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The dual-platform test gate

npm test runs the suite under two Jest projects with different transforms, environments and module resolution:

project	react-native resolves to	Platform.OS	renderer	transform
web	react-native-web	'web'	@testing-library/react → jsdom	ts-jest
native	the real react-native	'ios'	react-test-renderer	babel-jest (RN preset)

npm test           # both
npm run test:web
npm run test:native

Each project asserts what its platform actually emits — the web suite resolves aria-describedby through the DOM to real text; the native suite asserts accessibilityHint === X. The disagreement is the product. If you ever find yourself making the two agree by weakening an assertion, stop.

Both projects also assert their own platform identity (Platform.OS), so a moduleNameMapper leaking into the native project — which would quietly collapse it into a second copy of the web project — fails loudly instead of passing.