Give placeholder-only exposed filters a visually hidden label

Problem/Motivation

The header search (the header_search display of views.view.search, shipped by Varbase Search Base) exposes keywords with an empty label and the placeholder "Search by keyword". The field has no label on /contact-us, /newsletter, /advertise and /search, and a placeholder is gone once someone types.

Steps to reproduce

1. Install RightUp and open /search as anonymous.
2. The keywords field has no label.

Proposed resolution

In the theme form alter, give any exposed filter that has a placeholder and no title a visually hidden label from its placeholder. It is in the served HTML, no JavaScript.

The duplicate id views-exposed-form-search-header-search comes from the RightUp recipe placing the same search block twice on one page (header and mobile menu). That is left to the recipe.

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ✅ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• A visually hidden label on unlabelled exposed filters. Nothing visible changes.

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A

AI-Generated: Yes