fix(template-anchor-has-content): only treat bare-mustache hidden={{false}} as omitted; add test

Author: johanrd

lib/rules/template-anchor-has-content.js

@@ -27,6 +27,26 @@ function isAriaHiddenTrue(attr) {
   return resolved.trim().toLowerCase() === 'true';
 }
 
+// True if the HTML boolean `hidden` attribute renders as present at runtime.
+// Per docs/glimmer-attribute-behavior.md, only bare-mustache boolean-false
+// (`hidden={{false}}`) is omitted at runtime. Concat (`hidden="{{false}}"`)
+// and string-literal (`hidden={{"false"}}`) forms keep the attribute present
+// (and HTML treats any presence — including value "false" — as ON).
+function rendersHidden(attr) {
+  if (!attr) {
+    return false;
+  }
+  const v = attr.value;
+  if (
+    v?.type === 'GlimmerMustacheStatement' &&
+    v.path?.type === 'GlimmerBooleanLiteral' &&
+    v.path.value === false
+  ) {
+    return false;
+  }
+  return true;
+}
+
 // True if the anchor itself declares an accessible name via a statically
 // non-empty `aria-label`, `aria-labelledby`, or `title`, OR via a dynamic
 // value (we can't know at lint time whether a mustache resolves to an empty
@@ -105,7 +125,7 @@ function evaluateChild(child, sourceCode) {
     // from the accessibility tree — equivalent to aria-hidden="true" for
     // accessible-name purposes. A <span hidden>Backup</span> inside an
     // anchor contributes no name at runtime.
-    if (attrs.some((a) => a.name === 'hidden')) {
+    if (rendersHidden(attrs.find((a) => a.name === 'hidden'))) {
       return { dynamic: false, accessible: false };
     }
 
@@ -216,8 +236,7 @@ module.exports = {
         // `hidden` boolean attribute (element is not rendered at all) or
         // `aria-hidden="true"` (element removed from the accessibility tree).
         // In both cases, "accessible name of an anchor" is moot.
-        const hasHidden = attrs.some((a) => a.name === 'hidden');
-        if (hasHidden) {
+        if (rendersHidden(attrs.find((a) => a.name === 'hidden'))) {
           return;
         }
         const ariaHiddenAttr = attrs.find((a) => a.name === 'aria-hidden');

tests/lib/rules/template-anchor-has-content.js

@@ -145,6 +145,15 @@ ruleTester.run('template-anchor-has-content', rule, {
       output: null,
       errors: [{ messageId: 'anchorHasContent' }],
     },
+    // hidden={{false}} is the bare-mustache boolean-false case — Glimmer omits
+    // the attribute at runtime (per docs/glimmer-attribute-behavior.md), so
+    // the anchor is rendered and visible; an empty body still needs a name.
+    {
+      filename: 'test.gjs',
+      code: '<template><a href="/x" hidden={{false}}></a></template>',
+      output: null,
+      errors: [{ messageId: 'anchorHasContent' }],
+    },
     // Empty anchor.
     {
       filename: 'test.gjs',