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

[johanrd]

Note

This is part of a series where Claude has audited eslint-plugin-ember against jsx-a11y, vuejs-accessibility, angular-eslint, lit-a11y and html-validate, ember-template-lint, and the HTML and WCAG specs.

Summary

• Premise 1: <iframe> elements require an accessible name so assistive tech can convey their content. The normative source is WCAG SC 4.1.2 Name, Role, Value; Technique H64 is a sufficient technique citing title as one way to provide it.

• Premise 2: Mustache literal title values don't supply an author-intended name. At runtime Ember either drops the attribute when the bound value is nullish (no accessible name) or stringifies the literal to "null" / "undefined" / "42" (a coerced placeholder). Empty string literals like {{""}} resolve to "" — same effect as title="".

• Premise 3: Today our rule only rejects title={{false}}. title={{null}}, title={{undefined}}, title={{42}}, title={{""}}, and their title="{{x}}" concat equivalents silently pass.

• Conclusion: Treat GlimmerBooleanLiteral, GlimmerNullLiteral, GlimmerUndefinedLiteral, GlimmerNumberLiteral, and empty/whitespace GlimmerStringLiteral as invalid title values in both the title={{x}} and title="{{x}}" positions.

Fix: extract isInvalidTitleLiteralPath() for the four non-string literal types and a shared processStaticTitle() helper that handles text-node, mustache-string-literal, and concat-string-literal forms uniformly. Empty / whitespace string literals follow the same emptiness path as text-node title="".

Tests cover each literal type × each syntax form (bare-mustache and concat).

Whitespace-only title — now opt-out via schema option

The rule previously flagged title=" " (whitespace-only static) as a hard error. This is stricter than ACCNAME — ACCNAME 1.2 §4.3.2 step 2I (Tooltip) just says "return its value" with no trim (unlike step D AriaLabel, which has an explicit nor, when trimmed of whitespace, is not the empty string check), so a 3-space accessible name is technically assigned. The check remains on by default as an authoring-hygiene guard (useless in practice), but teams that want spec-aligned behavior can opt out via the new allowWhitespaceOnlyTitle: true option. Empty-string title="", the non-string literal cases above, and empty-string-literal mustaches are not affected by this option — they are always flagged as correctness.

Prior art

Peers diverge materially on empty/non-string title handling. Don't assume parity:

Plugin	Rule	Verified behavior
jsx-a11y	iframe-has-title	Check is if (title && typeof title === 'string') → bail. Flags title="" (falsy), flags title={42} (not a string), flags title={null} (falsy). Does NOT flag title=" " (truthy string).
vuejs-accessibility	iframe-has-title	Check is title === null || !["string","object"].includes(typeof title) → flag. Does NOT flag title="" (typeof "string"). Flags :title='2' (number not a string).
lit-a11y	iframe-title	Existence-only at line 38: !element.attribs.title || element.attribs.title === undefined. Flags title="" (falsy), does NOT flag non-string values (parse5 yields strings only).
@angular-eslint/template	—	No iframe-title equivalent in the rules directory.

[NullVoxPopuli]

why would we want to allow this?

[johanrd]

Hehe, basically because I (johan) didn't dare to have strict opinions on the behavior. but I feel somewhat silly defending it.

The option exists because the default is stricter than spec — it's an authoring-hygiene guard, not a normative requirement. Two relevant ACCNAME 1.2 steps from https://www.w3.org/TR/accname-1.2/#computation-steps. title=" " technically produces a three-space accessible name — spec-compliant, useless in practice. The option lets teams opt back to what the spec actually requires rather than our stricter default.

I doubt anyone will intentionally write a whitespace-only title. Should probably drop the option entirely and always flag it

[johanrd]

removed it now