Extract rule: template-require-valid-form-groups

[NullVoxPopuli]

Split from #2371.

[NullVoxPopuli-ai-agent]

Review: template-require-valid-form-groups (PR #2615)

Comparison with ember-template-lint source

General correctness:

1. Parent traversal mechanism: The original ETL uses path.parents() to walk up the ancestor chain, checking all ElementNode ancestors. The ESLint version uses node.parent and manually walks up. This depends on whether the Glimmer ESLint parser sets .parent on nodes. If it does, this works equivalently. If not, hasValidGroupingAncestor would always return false, causing false positives.

2. legend tag handling differs: The original ETL checks ['legend', 'fieldset'].includes(node.tag) — meaning a <legend> tag itself is treated as a valid form group ancestor. The ESLint version does the same in isValidFormGroup. However, <legend> alone doesn't group form controls — it's <fieldset> that does the grouping, with <legend> as its label. Including <legend> as a valid grouping ancestor is technically wrong in both versions, but at least they match.

3. hasMultipleFormElementsInParentScope relies on node.parent: The function checks node.parent and requires it to be a GlimmerElementNode. If the parent is the template root (e.g., GlimmerTemplate), this returns false, meaning form elements directly under the template root would never be flagged. The original ETL checks path.parent.node.type === 'ElementNode' — same behavior.

4. Only checks input elements: Both versions only check <input> elements via FORM_ELEMENTS. Other form elements like <select>, <textarea> are not checked. This matches the original.

Scope analysis (gjs/gts):

Not applicable. This rule checks HTML element tags (input, fieldset, legend) and attributes (role, aria-labelledby). No helper/component name matching.

Tests: Test coverage matches the original ETL tests. Both gjs and hbs modes tested.

Summary: Faithful migration. The main concern is whether node.parent is reliably set by the Glimmer ESLint parser — if so, this is correct.

🤖 Automated review comparing with ember-template-lint source