fix(template-require-valid-alt-text): reject empty-string aria-label/aria-labelledby/alt

Before: for <input type="image">, <object>, and <area>, the rule checked
only for the PRESENCE of an accessible-name fallback attribute
(aria-label / aria-labelledby / alt / title). An empty-string value
provides no accessible name but slipped past.

Fix: add hasNonEmptyTextAttr() that requires the attribute's static
value to be non-whitespace. Dynamic values (mustache, concat) remain
accepted — we can't tell at lint time whether they resolve to empty.

<img>'s alt handling is unchanged — alt="" is still valid there
(spec-defined marker for decorative images).

Nine new invalid tests cover the three elements × three fallback attrs.

Author: johanrd

lib/rules/template-require-valid-alt-text.js

@@ -12,6 +12,26 @@ function hasAnyAttr(node, names) {
   return names.some((name) => hasAttr(node, name));
 }
 
+// For accessible-name fallback attributes (aria-label, aria-labelledby, title),
+// an empty string provides no accessible name — it must be checked as "any truthy
+// static value" or "any dynamic value". Returns true iff the attribute is
+// present AND will meaningfully contribute an accessible name.
+function hasNonEmptyTextAttr(node, name) {
+  const attr = findAttr(node, name);
+  if (!attr?.value) {
+    return false;
+  }
+  if (attr.value.type === 'GlimmerTextNode') {
+    return attr.value.chars.trim() !== '';
+  }
+  // Mustache / concat — dynamic; assume truthy.
+  return true;
+}
+
+function hasAnyNonEmptyTextAttr(node, names) {
+  return names.some((name) => hasNonEmptyTextAttr(node, name));
+}
+
 function getTextValue(attr) {
   if (!attr?.value) {
     return undefined;
@@ -166,7 +186,9 @@ module.exports = {
               return;
             }
 
-            if (!hasAnyAttr(node, ['aria-label', 'aria-labelledby', 'alt'])) {
+            // Empty-string aria-label/aria-labelledby/alt provides no accessible
+            // name — require a non-empty fallback value.
+            if (!hasAnyNonEmptyTextAttr(node, ['aria-label', 'aria-labelledby', 'alt'])) {
               context.report({ node, messageId: 'inputImage' });
             }
 
@@ -177,7 +199,7 @@ module.exports = {
             const roleValue = getTextValue(roleAttr);
 
             if (
-              hasAnyAttr(node, ['aria-label', 'aria-labelledby', 'title']) ||
+              hasAnyNonEmptyTextAttr(node, ['aria-label', 'aria-labelledby', 'title']) ||
               hasChildren(node) ||
               (roleValue && ['presentation', 'none'].includes(roleValue))
             ) {
@@ -189,7 +211,7 @@ module.exports = {
             break;
           }
           case 'area': {
-            if (!hasAnyAttr(node, ['aria-label', 'aria-labelledby', 'alt'])) {
+            if (!hasAnyNonEmptyTextAttr(node, ['aria-label', 'aria-labelledby', 'alt'])) {
               context.report({ node, messageId: 'areaMissing' });
             }
 

tests/lib/rules/template-require-valid-alt-text.js

@@ -59,6 +59,53 @@ ruleTester.run('template-require-valid-alt-text', rule, {
     '<template><img role={{unless this.altText "presentation"}} alt={{this.altText}}></template>',
   ],
   invalid: [
+    // Empty-string aria-label / aria-labelledby / alt provides no accessible
+    // name. These must flag (previously accepted by a presence-only check).
+    {
+      code: '<template><input type="image" aria-label="" /></template>',
+      output: null,
+      errors: [{ messageId: 'inputImage' }],
+    },
+    {
+      code: '<template><input type="image" aria-labelledby="" /></template>',
+      output: null,
+      errors: [{ messageId: 'inputImage' }],
+    },
+    {
+      code: '<template><input type="image" alt="" /></template>',
+      output: null,
+      errors: [{ messageId: 'inputImage' }],
+    },
+    {
+      code: '<template><object aria-label=""></object></template>',
+      output: null,
+      errors: [{ messageId: 'objectMissing' }],
+    },
+    {
+      code: '<template><object aria-labelledby=""></object></template>',
+      output: null,
+      errors: [{ messageId: 'objectMissing' }],
+    },
+    {
+      code: '<template><object title=""></object></template>',
+      output: null,
+      errors: [{ messageId: 'objectMissing' }],
+    },
+    {
+      code: '<template><area aria-label=""></template>',
+      output: null,
+      errors: [{ messageId: 'areaMissing' }],
+    },
+    {
+      code: '<template><area aria-labelledby=""></template>',
+      output: null,
+      errors: [{ messageId: 'areaMissing' }],
+    },
+    {
+      code: '<template><area alt=""></template>',
+      output: null,
+      errors: [{ messageId: 'areaMissing' }],
+    },
     {
       code: '<template><img src="/test.jpg" /></template>',
       output: null,