# Form Field Shell

## Objective

Wrap every input in one structure so labels, help, and errors behave the same everywhere.

A single wrapper owning the label, description, error, and status region around any control in the app.

## Before You Begin

This feature is being added to an application that already exists and already
works. Do not scaffold a new project, and do not assume a blank slate.

Inspect the codebase first and establish:

- The existing application structure and where code of this kind already lives.
- The framework and version in use.
- The existing design system — colours, spacing, typography, and component conventions.
- Existing UI components you can reuse instead of writing new ones.
- The existing database structure, if this feature needs to persist anything.
- The existing authentication and authorization system, if this feature is user-scoped.
- Dependencies already installed, so you don't add a library that duplicates one.
- The existing test setup and conventions.

Only start writing code once you understand the above. If the application
already implements part of this feature, extend it rather than replacing it.

## Implementation Instructions

1. Inventory the app's existing fields and find the variations that have accumulated — label above versus beside, error under versus in a tooltip — then route all of them through one shell.
2. Generate a stable identifier per field and use it to link the control to its label, its description, and its error, so the association survives re-renders and does not collide when the same field appears twice on a page.
3. Support required, optional, read-only, and disabled as declared states of the shell, and let the shell pass them to the control rather than each screen setting them by hand.
4. Accept custom controls — comboboxes, date pickers, rich text, file drops — not only native inputs, by letting the shell hand its identifiers to whatever renders inside it.
5. Do not have the shell announce the error and also leave the control announcing its own. One error, one announcement; duplicated messages make a screen reader read the same sentence twice.

## UI and UX Requirements

Match the application's existing design system exactly. Reuse its components,
spacing, and typography. This feature should look like it was always there.

## Responsive Requirements

Works on mobile, tablet, and desktop. Touch targets are large enough to hit on a
phone, and nothing overflows horizontally at 320px.

## Accessibility Requirements

- Fully keyboard navigable.
- Correct semantic elements and ARIA roles.
- Visible focus states.
- Meets WCAG AA contrast.
- Dynamic changes are announced to screen readers.
- Respects prefers-reduced-motion.

## Edge Cases

- Identifiers must be stable across renders and unique across the page — a field repeated inside a repeating group must not point two controls at one label.
- Required, optional, read-only, and disabled are four different things and must be visually and programmatically distinct; a read-only field is still readable and copyable, a disabled one is not.
- An error announced by both the shell's live region and the control's own validation message is read twice; decide which one speaks and silence the other.
- A custom control that renders no native input still needs the label association, the error link, and a focusable element, or the shell will describe something the user cannot reach.
- Help text and error text must both be linked to the control, and when an error appears the description must not be dropped from the association — the user still needs the format rule.
- A field whose label is visually hidden by design still requires an accessible name; no field may rely on placeholder text as its label.
- The wording, placement, and conditional behaviour of the description are owned by Help Text Pattern, and the required marker is owned by Required Field Indicator — this shell owns the slots and the wiring, not the copy.

## Testing

Exercise the feature end to end in the running application. Cover every edge case
above, then run the existing test suite and confirm nothing regressed.

## Acceptance Criteria

- [ ] Every input in the app renders inside the same shell.
- [ ] Each control is programmatically linked to its label, its description, and its error.
- [ ] Required, optional, read-only, and disabled render distinctly and are exposed to assistive technology.
- [ ] Custom controls use the shell with the same associations as native inputs.
- [ ] An error is announced exactly once.
- [ ] Repeating a field within a page produces no duplicate identifiers.
- [ ] The feature matches the existing design system.
- [ ] No existing functionality is broken.

## Adaptation Rules

- Match the existing design system. Do not introduce a new colour palette,
  spacing scale, or component library.
- Reuse existing components and utilities wherever they fit.
- Follow the naming, file layout, and code style already present.
- Do not upgrade, replace, or remove existing dependencies to make this
  feature fit. Adapt the feature to the app, not the app to the feature.
- Do not break existing functionality. If a change is genuinely required in
  existing code, make the smallest one that works and say so.
- If something in these instructions conflicts with how the application is
  built, follow the application and explain the deviation.

## Final Verification

Before you report the work as done:

1. Re-read the acceptance criteria above and check each one against what you
   actually built.
2. Run the application and exercise the feature end to end.
3. Run the existing test suite and confirm you have broken nothing.
4. Check the feature on mobile, tablet, and desktop widths.
5. Check keyboard navigation and focus handling.
6. Summarize what changed: files added, files modified, and anything you
   deliberately did differently because of how this application is built.

If any acceptance criterion is unmet, fix it before reporting completion.