BUGFIX: template-no-empty-headings — recognize boolean aria-hidden

docs/rules/template-no-empty-headings.md

@@ -50,6 +50,21 @@ This rule **allows** the following:
 
 If violations are found, remediation should be planned to ensure text content is present and visible and/or screen-reader accessible. Setting `aria-hidden="false"` or removing `hidden` attributes from the element(s) containing heading text may serve as a quickfix.
 
+## Notes on `aria-hidden` semantics
+
+This rule treats valueless / empty-string `aria-hidden` (`<h1 aria-hidden>` or `<h1 aria-hidden="">`) as exempting the heading from the empty-content check — those forms count as "hidden" for this rule.
+
+**This is a deliberate deviation from [WAI-ARIA 1.2 §`aria-hidden`](https://www.w3.org/TR/wai-aria-1.2/#aria-hidden)**, which resolves valueless / empty-string `aria-hidden` to the default value `undefined` — not `true` — and therefore does not hide the element per spec. The spec-literal reading would say "valueless `aria-hidden` doesn't hide, so the empty heading is still a violation."
+
+We lean toward fewer false positives here: if the author wrote `aria-hidden` at all, they signaled an intent to hide, and flagging the empty heading on top of what is already a malformed `aria-hidden` usage layers a second-order complaint on a first-order problem. Axe-core and the W3C ACT rules consistently treat this shape as INCOMPLETE (needs manual review) rather than a definitive failure, which is consistent with leaning away from a hard flag here.
+
+For rules that ask the _opposite_ question ("is this element authoritatively hidden?"), the spec-literal reading applies — see e.g. `template-no-aria-hidden-on-focusable` and `template-anchor-has-content`, which treat valueless `aria-hidden` as **not** hidden. This split is applied per-rule, picking the interpretation that produces the fewest false positives for each specific check.
+
+Unambiguous forms always follow the spec:
+
+- `aria-hidden="true"` / `aria-hidden={{true}}` / `aria-hidden={{"true"}}` (any case) → hidden, exempts the heading.
+- `aria-hidden="false"` / `aria-hidden={{false}}` / `aria-hidden={{"false"}}` → not hidden, the empty-content check still applies.
+
 ## References
 
 - [WCAG SC 2.4.6 Headings and Labels](https://www.w3.org/TR/UNDERSTANDING-WCAG20/navigation-mechanisms-descriptive.html)

lib/rules/template-no-empty-headings.js

@@ -1,17 +1,55 @@
 const HEADINGS = new Set(['h1', 'h2', 'h3', 'h4', 'h5', 'h6']);
 
+// aria-hidden semantics for valueless / empty / "false" are genuinely
+// contested — four ecosystem positions exist (jsx-a11y / vue-a11y / axe /
+// WAI-ARIA spec), see PR body. This rule leans toward FEWER false positives:
+// when the author has written `aria-hidden` in any form that could plausibly
+// mean "hide this", we exempt the heading from the empty-content check. The
+// downside (missing some genuinely-empty headings) is preferable to flagging
+// correctly-authored headings the developer intentionally decorated.
+//
+// Truthy:
+//  - valueless attr (`<h1 aria-hidden>`) — default-undefined per spec, but
+//    authors who write bare `aria-hidden` plausibly intend hidden.
+//  - empty string `aria-hidden=""` — same.
+//  - `aria-hidden="true"` / "TRUE" / "True" (ASCII case-insensitive).
+//  - `aria-hidden={{true}}` mustache boolean literal.
+//  - `aria-hidden={{"true"}}` / case-variants as mustache string literal.
+// Not truthy (falls through):
+//  - `aria-hidden="false"` / `{{false}}` / `{{"false"}}` — explicit opt-out.
+function isAriaHiddenTruthy(attr) {
+  if (!attr) {
+    return false;
+  }
+  const value = attr.value;
+  // Valueless attribute — no `value` property at all.
+  if (!value) {
+    return true;
+  }
+  if (value.type === 'GlimmerTextNode') {
+    const chars = value.chars.toLowerCase();
+    // Empty string is exempted (lean toward fewer false positives).
+    return chars === '' || chars === 'true';
+  }
+  if (value.type === 'GlimmerMustacheStatement' && value.path) {
+    if (value.path.type === 'GlimmerBooleanLiteral') {
+      return value.path.value === true;
+    }
+    if (value.path.type === 'GlimmerStringLiteral') {
+      return value.path.value.toLowerCase() === 'true';
+    }
+  }
+  return false;
+}
+
 function isHidden(node) {
   if (!node.attributes) {
     return false;
   }
   if (node.attributes.some((a) => a.name === 'hidden')) {
     return true;
   }
-  const ariaHidden = node.attributes.find((a) => a.name === 'aria-hidden');
-  if (ariaHidden?.value?.type === 'GlimmerTextNode' && ariaHidden.value.chars === 'true') {
-    return true;
-  }
-  return false;
+  return isAriaHiddenTruthy(node.attributes.find((a) => a.name === 'aria-hidden'));
 }
 
 function isComponent(node) {

tests/lib/rules/template-no-empty-headings.js

@@ -43,6 +43,17 @@ ruleTester.run('template-no-empty-headings', rule, {
     '<template><h1><this.Heading /></h1></template>',
     '<template><h2><@heading /></h2></template>',
     '<template><h3><ns.Heading /></h3></template>',
+
+    // aria-hidden variants — exempt from empty-heading check (fewer-false-
+    // positives policy; see PR body for the four ecosystem positions).
+    '<template><h1 aria-hidden></h1></template>',
+    '<template><h1 aria-hidden=""></h1></template>',
+    '<template><h1 aria-hidden={{true}}></h1></template>',
+    '<template><h1 aria-hidden="true">Visible to sighted only</h1></template>',
+    '<template><h1 aria-hidden="TRUE"></h1></template>',
+    '<template><h1 aria-hidden="True"></h1></template>',
+    '<template><h1 aria-hidden={{"TRUE"}}></h1></template>',
+    '<template><h1 aria-hidden={{"True"}}></h1></template>',
   ],
   invalid: [
     {
@@ -132,5 +143,23 @@ ruleTester.run('template-no-empty-headings', rule, {
       output: null,
       errors: [{ messageId: 'emptyHeading' }],
     },
+
+    // Explicit falsy aria-hidden does NOT exempt the empty-heading check —
+    // this is the unambiguous opt-out, no ecosystem position disagrees.
+    {
+      code: '<template><h1 aria-hidden="false"></h1></template>',
+      output: null,
+      errors: [{ messageId: 'emptyHeading' }],
+    },
+    {
+      code: '<template><h1 aria-hidden={{false}}></h1></template>',
+      output: null,
+      errors: [{ messageId: 'emptyHeading' }],
+    },
+    {
+      code: '<template><h1 aria-hidden={{"false"}}></h1></template>',
+      output: null,
+      errors: [{ messageId: 'emptyHeading' }],
+    },
   ],
 });