Update: legend to provide name to optgroup

[scottaohara]

In regards to the updated content model for the select element and its allowed children, an optgroup can have a legend element as its first child, and this legend needs to be able to name the optgroup similarly to how a legend names a fieldset.

see: https://github.com/whatwg/html/pull/10586

WPT - https://github.com/web-platform-tests/wpt/pull/49645

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[scottaohara]

@keithamus would you mind taking another look? I've updated the ordering for the optgroup naming, and added new content to how a description should be calculated.

cc @josepharhar as updates here related to my comments in the update content model for customized select PR

[scottaohara]

examples for tests for how name/desc steps should work

## Name from aria-labelledby and description expectation tests

test 1: name = foo
        description = n/a
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-labelledby=f>
       <div id=f>foo</div> <!-- invalid per content model -->
       <option>test
    </optgroup>
</select>


test 2: name = foo
        description = n/a
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-labelledby=f aria-label=bar>
       <div id=f>foo</div> <!-- invalid per content model -->
       <option>test
    </optgroup>
</select>


test 3: name = foo
        description = bar
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-labelledby=f title=bar>
       <div id=f>foo</div> <!-- invalid per content model -->
       <option>test
    </optgroup>
</select>


## Name from aria-label and description expectation tests

test 1: name = foo
        description = n/a
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-label=foo>
        <option>test
    </optgroup>
</select>

test 2: name = foo
        description = bar
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-label=foo title=bar>
        <option>test
    </optgroup>
</select>



## Name from label attribute and description expectation tests

test 1: name = foo
        description = n/a
<!-- primary use case, no naming mechanism aside from label attribute -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup label=foo>
        <option>test
    </optgroup>
</select>


test 2: name = bar
        description = foo
<!-- aria-label provided which wins out over label attr, but label attr's value is rendered, so still
     expose it as a description so the information is at least still available to AT -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-label=bar label=foo>
        <option>test
    </optgroup>
</select>


test 3: name = foo
        description = bar
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup label=foo title=bar>
        <option>test
    </optgroup>
</select>


## Name from legend element and description expectation tests

test 1: name = foo 
        description = n/a
<!-- primary use case, no naming mechanism aside from legend element -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup>
        <legend>foo</legend>
        <option>test
    </optgroup>
</select>

test 2: name = foo 
        description = n/a
<!-- label attr value is not to render because legend is specified -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup label=bar>
        <legend>foo</legend>
        <option>test
    </optgroup>
</select>

test 3: name = bar 
        description = foo
<!-- aria-label provided which wins out over legend, but legend is rendered, so still
     expose it as a description so the information is at least still available to AT -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-label=bar>
        <legend>foo</legend>
        <option>test
    </optgroup>
</select>

test 4: name = bar 
        description = foo
<!-- aria-labelledby provided which wins out over legend, but legend is rendered, so still
     expose it as a description so the information is at least still available to AT -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-labelledby=b>
        <div id=b>bar</div> <!-- invalid per content model -->
        <legend>foo</legend>
        <option>test
    </optgroup>
</select>


test 5: name = foo 
        description = bar
<!-- legend provides name, title provides description -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup title=bar>
        <legend>foo</legend>
        <option>test
    </optgroup>
</select>


## Name from title attribute and description expectation tests

test 1: name = foo 
        description = n/a
<!-- primary use case, no naming mechanism provided aside from title attribute -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup title=foo>
        <option>test
    </optgroup>
</select>


test 2: name = foo 
        description = n/a
<!-- empty label would otherwise result in no accName - use title as fallback -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup label title=foo>
        <option>test
    </optgroup>
</select>

test 3: name = foo 
        description = n/a
<!-- empty legend would otherwise result in no accName - use title as fallback -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup title=foo>
        <legend></legend>
        <option>test
    </optgroup>
</select>

test 4: name = foo
        description = n/a
<!-- empty aria-label would otherwise result in no accName - use title as fallback -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-label title=foo>
        <legend></legend>
        <option>test
    </optgroup>
</select>

test 5: name = foo
        description = n/a
<!-- aria-labelledby points to empty element which would otherwise result in no accName - use title as fallback -->
<select>
    <button><selectedcontent></selectedcontent></button>
    <optgroup aria-labelledby=f title=foo>
        <div id=f></div>
        <legend></legend>
        <option>test
    </optgroup>
</select>

[scottaohara]

put back into the draft state as I need to revise the bits about how a label attribute and legend element should no longer be expected to render at the same time. re: https://issues.chromium.org/issues/378601807

[josepharhar]

put back into the draft state as I need to revise the bits about how a label attribute and legend element should no longer be expected to render at the same time. re: https://issues.chromium.org/issues/378601807

If you have a recommendation for what to do in this case, let me know and/or comment on the crbug. I haven't implemented anything yet to account for the case where both are present.

[scottaohara]

@josepharhar i think it's totally fine to only have one render / and have a preference for the legend element in this case since it'll allow for authors to do more.

• if only label attribute is specified, render that to be consistent with prior select functionality
• if only legend is specified, render that and if the select is loaded in a browser that doesn't support customization, there is no fallback
• if both are specified,
  • in browsers that support customization render legend element as the group label and do not render label attribute text
  • in browsers that don't support customization render the fallback label attribute text as the group label

[spectranaut]

@scottaohara does this need implementation changes? If so I'll add the PR tracking list.

[spectranaut]

Discussed briefly in last weeks meeting: https://www.w3.org/2025/06/26-aria-minutes.html#58a8