BUGFIX: template-require-iframe-title — flag title={{null|undefined|number}}

docs/rules/template-require-iframe-title.md

@@ -6,9 +6,11 @@
 
 ## `<iframe>`
 
-`<iframe>` elements must have a unique title property to indicate its content to the user.
-
-This rule takes no arguments.
+`<iframe>` elements must have a unique title property so assistive
+technology can convey their content to the user. The normative
+requirement is [WCAG SC 4.1.2 (Name, Role, Value)](https://www.w3.org/TR/UNDERSTANDING-WCAG20/ensure-compat-rsv.html);
+the `title` attribute is _one sufficient technique_ for meeting it
+(sufficient technique [H64](https://www.w3.org/WAI/WCAG21/Techniques/html/H64)).
 
 ## Examples
 
@@ -27,12 +29,21 @@ This rule **forbids** the following:
 <template>
   <iframe />
   <iframe title='' />
+  <iframe title='   ' />
+  <iframe title={{null}} />
+  <iframe title={{undefined}} />
+  <iframe title={{true}} />
+  <iframe title={{false}} />
+  <iframe title={{42}} />
 </template>
 ```
 
 ## References
 
-- [Deque University](https://dequeuniversity.com/rules/axe/1.1/frame-title)
-- [Technique H65: Using the title attribute of the frame and iframe elements](https://www.w3.org/TR/2014/NOTE-WCAG20-TECHS-20140408/H64)
-- [WCAG Success Criterion 2.4.1 - Bypass Blocks](https://www.w3.org/TR/UNDERSTANDING-WCAG20/navigation-mechanisms-skip.html)
-- [WCAG Success Criterion 4.1.2 - Name, Role, Value](https://www.w3.org/TR/UNDERSTANDING-WCAG20/ensure-compat-rsv.html)
+- [WCAG SC 4.1.2 — Name, Role, Value](https://www.w3.org/TR/UNDERSTANDING-WCAG20/ensure-compat-rsv.html)
+  — the normative requirement.
+- [WCAG Technique H64 — Using the title attribute of the iframe element](https://www.w3.org/WAI/WCAG21/Techniques/html/H64)
+  — a sufficient technique for SC 4.1.2, not itself normative.
+- [WCAG Success Criterion 2.4.1 — Bypass Blocks](https://www.w3.org/TR/UNDERSTANDING-WCAG20/navigation-mechanisms-skip.html)
+- [ACCNAME 1.2 — accessible-name computation](https://www.w3.org/TR/accname-1.2/)
+- [axe-core rule `frame-title`](https://dequeuniversity.com/rules/axe/4.10/frame-title)

lib/rules/template-no-yield-only.js

@@ -1,3 +1,11 @@
+function isEmptyNode(node) {
+  return (
+    node.type === 'GlimmerMustacheCommentStatement' ||
+    node.type === 'GlimmerCommentStatement' ||
+    (node.type === 'GlimmerTextNode' && !node.chars.trim())
+  );
+}
+
 function isYieldOnly(node) {
   return (
     node.type === 'GlimmerMustacheStatement' &&
@@ -44,7 +52,8 @@ module.exports = {
             ? node.body[0].children
             : node.body;
 
-        if (templateNodes.length === 1 && isYieldOnly(templateNodes[0])) {
+        const nonEmptyNodes = templateNodes.filter((n) => !isEmptyNode(n));
+        if (nonEmptyNodes.length === 1 && isYieldOnly(nonEmptyNodes[0])) {
           isOnlyYield = true;
         }
       },

lib/rules/template-require-iframe-title.js

@@ -1,3 +1,43 @@
+'use strict';
+
+// Non-string literal AST nodes (boolean/null/undefined/number) don't represent
+// a meaningful author-provided title. Even though they would coerce to strings
+// at runtime (e.g. `true` → "true", `42` → "42"), those strings do not describe
+// the frame's content — the rule rejects the literal forms.
+const INVALID_LITERAL_TYPES = new Set([
+  'GlimmerBooleanLiteral',
+  'GlimmerNullLiteral',
+  'GlimmerUndefinedLiteral',
+  'GlimmerNumberLiteral',
+]);
+
+function isInvalidTitleLiteralPath(path) {
+  return INVALID_LITERAL_TYPES.has(path?.type);
+}
+
+function getInvalidLiteralType(path) {
+  if (!path) {
+    return undefined;
+  }
+  switch (path.type) {
+    case 'GlimmerBooleanLiteral': {
+      return 'boolean';
+    }
+    case 'GlimmerNullLiteral': {
+      return 'null';
+    }
+    case 'GlimmerUndefinedLiteral': {
+      return 'undefined';
+    }
+    case 'GlimmerNumberLiteral': {
+      return 'number';
+    }
+    default: {
+      return undefined;
+    }
+  }
+}
+
 /** @type {import('eslint').Rule.RuleModule} */
 module.exports = {
   meta: {
@@ -8,13 +48,15 @@ module.exports = {
       url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-require-iframe-title.md',
       templateMode: 'both',
     },
+    fixable: null,
     schema: [],
     messages: {
-      // Four messageIds (missingTitle, emptyTitle, dynamicFalseTitle,
-      // duplicateTitle) for richer diagnostic detail.
+      // Five messageIds (missingTitle, emptyTitle, invalidTitleLiteral,
+      // duplicateTitleFirst, duplicateTitleOther) for richer diagnostic detail.
       missingTitle: '<iframe> elements must have a unique title property.',
       emptyTitle: '<iframe> elements must have a unique title property.',
-      dynamicFalseTitle: '<iframe> elements must have a unique title property.',
+      invalidTitleLiteral:
+        '<iframe title> must be a non-empty string. Got {{literalType}} literal, which does not describe the frame contents.',
       duplicateTitleFirst: 'This title is not unique. #{{index}}',
       duplicateTitleOther:
         '<iframe> elements must have a unique title property. Value title="{{title}}" already used for different iframe. #{{index}}',
@@ -34,6 +76,40 @@ module.exports = {
     const knownTitles = [];
     let nextDuplicateIndex = 1;
 
+    // Process a statically-known title string (from a text node OR a
+    // mustache string literal OR a single-part concat). Handles the empty /
+    // whitespace / duplicate logic that's shared across those AST shapes.
+    function processStaticTitle(node, raw) {
+      const value = raw.trim();
+      if (value.length === 0) {
+        context.report({ node, messageId: 'emptyTitle' });
+        return;
+      }
+      // Duplicate check — reports BOTH the first and the current occurrence
+      // on every collision, sharing a `#N` index so users can correlate them.
+      // For three or more duplicates the first occurrence is therefore
+      // re-reported once per collision.
+      const existing = knownTitles.find((entry) => entry.value === value);
+      if (existing) {
+        if (existing.index === null) {
+          existing.index = nextDuplicateIndex++;
+        }
+        const index = existing.index;
+        context.report({
+          node: existing.node,
+          messageId: 'duplicateTitleFirst',
+          data: { index: String(index) },
+        });
+        context.report({
+          node,
+          messageId: 'duplicateTitleOther',
+          data: { title: raw, index: String(index) },
+        });
+      } else {
+        knownTitles.push({ value, node, index: null });
+      }
+    }
+
     return {
       GlimmerElementNode(node) {
         if (node.tag !== 'iframe') {
@@ -57,57 +133,55 @@ module.exports = {
         if (titleAttr.value) {
           switch (titleAttr.value.type) {
             case 'GlimmerTextNode': {
-              const value = titleAttr.value.chars.trim();
-              if (value.length === 0) {
-                context.report({ node, messageId: 'emptyTitle' });
-              } else {
-                // Check for duplicate titles. Reports BOTH the first and the
-                // current occurrence on every collision, sharing a `#N` index
-                // so users can correlate them. For three or more duplicates
-                // the first occurrence is therefore re-reported once per
-                // collision.
-                const existing = knownTitles.find((entry) => entry.value === value);
-                if (existing) {
-                  if (existing.index === null) {
-                    existing.index = nextDuplicateIndex++;
-                  }
-                  const index = existing.index;
-
-                  // Report on the first occurrence on every collision.
-                  context.report({
-                    node: existing.node,
-                    messageId: 'duplicateTitleFirst',
-                    data: { index: String(index) },
-                  });
-
-                  // Report on the current (duplicate) occurrence.
-                  context.report({
-                    node,
-                    messageId: 'duplicateTitleOther',
-                    data: { title: titleAttr.value.chars, index: String(index) },
-                  });
-                } else {
-                  knownTitles.push({ value, node, index: null });
-                }
-              }
+              processStaticTitle(node, titleAttr.value.chars);
               break;
             }
             case 'GlimmerMustacheStatement': {
-              // title={{false}} → BooleanLiteral false is invalid
-              if (titleAttr.value.path?.type === 'GlimmerBooleanLiteral') {
-                context.report({ node, messageId: 'dynamicFalseTitle' });
+              // Non-string literal mustaches — boolean / null / undefined /
+              // number — get a specific "invalidTitleLiteral" diagnostic
+              // because the literal coerces to a string at runtime that
+              // doesn't describe the frame contents.
+              if (isInvalidTitleLiteralPath(titleAttr.value.path)) {
+                context.report({
+                  node,
+                  messageId: 'invalidTitleLiteral',
+                  data: { literalType: getInvalidLiteralType(titleAttr.value.path) },
+                });
+                break;
+              }
+              // String-literal mustaches resolve to their static value — a
+              // non-empty literal supplies an accessible name the same as a
+              // text node. Empty / whitespace literals are flagged the same
+              // way as `title=""` / `title="   "`.
+              if (titleAttr.value.path?.type === 'GlimmerStringLiteral') {
+                processStaticTitle(node, titleAttr.value.path.value);
               }
               break;
             }
             case 'GlimmerConcatStatement': {
-              // title="{{false}}" → ConcatStatement with single BooleanLiteral part
               const parts = titleAttr.value.parts || [];
+              // Single-part concat wrapping a non-string literal — same
+              // diagnostic as the bare mustache form.
+              if (
+                parts.length === 1 &&
+                parts[0].type === 'GlimmerMustacheStatement' &&
+                isInvalidTitleLiteralPath(parts[0].path)
+              ) {
+                context.report({
+                  node,
+                  messageId: 'invalidTitleLiteral',
+                  data: { literalType: getInvalidLiteralType(parts[0].path) },
+                });
+                break;
+              }
+              // Single-part concat wrapping a string literal — resolve to
+              // the static value and apply the same checks as a text node.
               if (
                 parts.length === 1 &&
                 parts[0].type === 'GlimmerMustacheStatement' &&
-                parts[0].path?.type === 'GlimmerBooleanLiteral'
+                parts[0].path?.type === 'GlimmerStringLiteral'
               ) {
-                context.report({ node, messageId: 'dynamicFalseTitle' });
+                processStaticTitle(node, parts[0].path.value);
               }
               break;
             }

tests/lib/rules/template-no-yield-only.js

@@ -30,6 +30,16 @@ const invalidHbs = [
     output: null,
     errors: [{ messageId: 'noYieldOnly' }],
   },
+  {
+    code: '{{!-- long-form comment --}}{{yield}}',
+    output: null,
+    errors: [{ messageId: 'noYieldOnly' }],
+  },
+  {
+    code: '<!-- html comment -->{{yield}}',
+    output: null,
+    errors: [{ messageId: 'noYieldOnly' }],
+  },
 ];
 
 function wrapTemplate(entry) {