fix: condition select→combobox implicit role on multiple/size

Per HTML-AAM, <select>'s implicit role is "combobox" only when neither
`multiple` nor `size > 1` is present; otherwise it is "listbox". The
previous commit added `combobox: ['select']` unconditionally, which
caused false positives for <select role="combobox" multiple> and
<select role="combobox" size="5"> (where combobox disagrees with the
implicit listbox role and therefore is not redundant).

Add a selectHasComboboxImplicitRole helper mirroring jsx-a11y's
src/util/implicitRoles/select.js, and short-circuit the redundancy
check for <select role="combobox"> when the implicit role is actually
listbox.

Update the code comment on the `combobox: ['select']` entry to reflect
this (and drop the inaccurate "§4.1" reference — the <select> mapping
lives in the HTML-AAM main conformance table, section 4, without a
numbered subsection).

Tests:
- valid: <select role="combobox" multiple></select>
- valid: <select role="combobox" size="5"></select>
- invalid: <select role="combobox" size="1"></select>  (size=1 → combobox)
- invalid: <select role="COMBOBOX"></select>           (case + implicit)

Author: johanrd

lib/rules/template-no-redundant-role.js

@@ -37,6 +37,25 @@ const ALLOWED_ELEMENT_ROLES = [
   { name: 'input', role: 'combobox' },
 ];
 
+// Per HTML-AAM, <select> maps to "combobox" only when neither `multiple` nor
+// `size > 1` is set; otherwise it maps to "listbox". Mirrors jsx-a11y's
+// src/util/implicitRoles/select.js.
+function selectHasComboboxImplicitRole(node) {
+  const attrs = node.attributes || [];
+  const hasMultiple = attrs.some((a) => a.name === 'multiple');
+  if (hasMultiple) {
+    return false;
+  }
+  const sizeAttr = attrs.find((a) => a.name === 'size');
+  if (sizeAttr && sizeAttr.value && sizeAttr.value.type === 'GlimmerTextNode') {
+    const sizeValue = Number(sizeAttr.value.chars);
+    if (Number.isFinite(sizeValue) && sizeValue > 1) {
+      return false;
+    }
+  }
+  return true;
+}
+
 // Mapping of roles to their corresponding HTML elements
 // From https://www.w3.org/TR/html-aria/
 const ROLE_TO_ELEMENTS = {
@@ -45,8 +64,9 @@ const ROLE_TO_ELEMENTS = {
   button: ['button'],
   cell: ['td'],
   checkbox: ['input'],
-  // <select> is a combobox by default (per HTML-AAM §4.1 — unless `multiple` or
-  // a `size > 1` is set, in which case it's a listbox; both mappings are listed).
+  // <select> is a combobox by default per HTML-AAM (section 4). When
+  // `multiple` is present or `size > 1`, it maps to "listbox" instead;
+  // that case is handled at the call site via selectHasComboboxImplicitRole.
   combobox: ['select'],
   columnheader: ['th'],
   complementary: ['aside'],
@@ -145,6 +165,18 @@ module.exports = {
           return;
         }
 
+        // <select role="combobox"> is only redundant when <select>'s implicit
+        // role actually is "combobox" (no `multiple`, and `size` absent or <= 1).
+        // Otherwise the implicit role is "listbox", so the explicit "combobox"
+        // is not redundant and this rule should not flag it.
+        if (
+          node.tag === 'select' &&
+          roleValue === 'combobox' &&
+          !selectHasComboboxImplicitRole(node)
+        ) {
+          return;
+        }
+
         const isRedundant =
           elementsWithRole.includes(node.tag) &&
           !ALLOWED_ELEMENT_ROLES.some((e) => e.name === node.tag && e.role === roleValue);

tests/lib/rules/template-no-redundant-role.js

@@ -48,6 +48,10 @@ ruleTester.run('template-no-redundant-role', rule, {
       options: [{ checkAllHTMLElements: false }],
     },
     '<template><input role="combobox"></template>',
+    // <select multiple> has implicit role listbox, so combobox is not redundant.
+    '<template><select role="combobox" multiple></select></template>',
+    // <select size="5"> (size > 1) has implicit role listbox.
+    '<template><select role="combobox" size="5"></select></template>',
   ],
   invalid: [
     {
@@ -155,6 +159,12 @@ hbsRuleTester.run('template-no-redundant-role', rule, {
       options: [{ checkAllHTMLElements: false }],
     },
     '<ul class="list" role="combobox"></ul>',
+    // <select> with `multiple` has implicit role "listbox", so role="combobox"
+    // is not redundant (it disagrees with the implicit role, but that is for
+    // other rules to catch — this rule only flags redundancy).
+    '<select role="combobox" multiple></select>',
+    // <select size="5"> (size > 1) has implicit role "listbox", same reasoning.
+    '<select role="combobox" size="5"></select>',
   ],
   invalid: [
     {
@@ -249,6 +259,18 @@ hbsRuleTester.run('template-no-redundant-role', rule, {
       output: '<select></select>',
       errors: [{ message: 'Use of redundant or invalid role: combobox on <select> detected.' }],
     },
+    {
+      // size="1" still defaults to combobox (only size > 1 flips to listbox).
+      code: '<select role="combobox" size="1"></select>',
+      output: '<select size="1"></select>',
+      errors: [{ message: 'Use of redundant or invalid role: combobox on <select> detected.' }],
+    },
+    {
+      // Case-insensitive match on <select>, combined with the implicit-role check.
+      code: '<select role="COMBOBOX"></select>',
+      output: '<select></select>',
+      errors: [{ message: 'Use of redundant or invalid role: combobox on <select> detected.' }],
+    },
     {
       // Case-insensitive matching — ARIA role tokens compare as ASCII-case-insensitive.
       code: '<body role="DOCUMENT"></body>',